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Zhang K, Zhang L, Cui Y, Yang Y, Wu J, Liang J, Li X, Zhang X, Zhang Y, Guo Z, Zhang L, Chen S, Ruan J, Freeling M, Wang X, Cheng F. The lack of negative association between TE load and subgenome dominance in synthesized Brassica allotetraploids. Proc Natl Acad Sci U S A 2023; 120:e2305208120. [PMID: 37816049 PMCID: PMC10589682 DOI: 10.1073/pnas.2305208120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 09/01/2023] [Indexed: 10/12/2023] Open
Abstract
Polyploidization is important to the evolution of plants. Subgenome dominance is a distinct phenomenon associated with most allopolyploids. A gene on the dominant subgenome tends to express to higher RNA levels in all organs as compared to the expression of its syntenic paralogue (homoeolog). The mechanism that underlies the formation of subgenome dominance remains unknown, but there is evidence for the involvement of transposon/DNA methylation density differences nearby the genes of parents as being causal. The subgenome with lower density of transposon and methylation near genes is positively associated with subgenome dominance. Here, we generated eight generations of allotetraploid progenies from the merging of parental genomes Brassica rapa and Brassica oleracea. We found that transposon/methylation density differ near genes between the parental (rapa:oleracea) existed in the wide hybrid, persisted in the neotetraploids (the synthetic Brassica napus), but these neotetraploids expressed no expected subgenome dominance. This absence of B. rapa vs. B. oleracea subgenome dominance is particularly significant because, while there is no negative relationship between transposon/methylation level and subgenome dominance in the neotetraploids, the more ancient parental subgenomes for all Brassica did show differences in transposon/methylation densities near genes and did express, in the same samples of cells, biased gene expression diagnostic of subgenome dominance. We conclude that subgenome differences in methylated transposon near genes are not sufficient to initiate the biased gene expressions defining subgenome dominance. Our result was unexpected, and we suggest a "nuclear chimera" model to explain our data.
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Affiliation(s)
- Kang Zhang
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Lingkui Zhang
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Yinan Cui
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
- Chengde Academy of Agriculture and Forestry Sciences, Chengde067032, China
| | - Yinqing Yang
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Jian Wu
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Jianli Liang
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Xing Li
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Xin Zhang
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Yiyue Zhang
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Zhongwei Guo
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Lei Zhang
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Shumin Chen
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Jue Ruan
- Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen518120, China
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA94720-3102
| | - Xiaowu Wang
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
| | - Feng Cheng
- State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture and Rural Affairs, Sino-Dutch Joint Laboratory of Horticultural Genomics, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing100081, China
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2
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Burgess D, Chow HT, Grover JW, Freeling M, Mosher RA. Ovule siRNAs methylate protein-coding genes in trans. Plant Cell 2022; 34:3647-3664. [PMID: 35781738 PMCID: PMC9516104 DOI: 10.1093/plcell/koac197] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 06/24/2022] [Indexed: 05/31/2023]
Abstract
Twenty-four-nucleotide (nt) small interfering RNAs (siRNAs) maintain asymmetric DNA methylation at thousands of euchromatic transposable elements in plant genomes in a process called RNA-directed DNA methylation (RdDM). RdDM is dispensable for growth and development in Arabidopsis thaliana, but is required for reproduction in other plants, such as Brassica rapa. The 24-nt siRNAs are abundant in maternal reproductive tissue, due largely to overwhelming expression from a few loci in the ovule and developing seed coat, termed siren loci. A recent study showed that 24-nt siRNAs produced in the anther tapetal tissue can methylate male meiocyte genes in trans. Here we show that in B. rapa, a similar process takes place in female tissue. siRNAs are produced from gene fragments embedded in some siren loci, and these siRNAs can trigger methylation in trans at related protein-coding genes. This trans-methylation is associated with silencing of some target genes and may be responsible for seed abortion in RdDM mutants. Furthermore, we demonstrate that a consensus sequence in at least two families of DNA transposons is associated with abundant siren expression, most likely through recruitment of CLASSY3, a putative chromatin remodeler. This research describes a mechanism whereby RdDM influences gene expression and sheds light on the role of RdDM during plant reproduction.
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3
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Zhang K, Yang Y, Wu J, Liang J, Chen S, Zhang L, Lv H, Yin X, Zhang X, Zhang Y, Zhang L, Zhang Y, Freeling M, Wang X, Cheng F. A cluster of transcripts identifies a transition stage initiating leafy head growth in heading morphotypes of Brassica. Plant J 2022; 110:688-706. [PMID: 35118736 PMCID: PMC9314147 DOI: 10.1111/tpj.15695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 01/24/2022] [Accepted: 01/26/2022] [Indexed: 05/10/2023]
Abstract
Leaf heading is an important and economically valuable horticultural trait in many vegetables. The formation of a leafy head is a specialized leaf morphogenesis characterized by the emergence of the enlarged incurving leaves. However, the transcriptional regulation mechanisms underlying the transition to leaf heading remain unclear. We carried out large-scale time-series transcriptome assays covering the major vegetative growth phases of two headingBrassica crops, Chinese cabbage and cabbage, with the non-heading morphotype Taicai as the control. A regulatory transition stage that initiated the heading process is identified, accompanied by a developmental switch from rosette leaf to heading leaf in Chinese cabbages. This transition did not exist in the non-heading control. Moreover, we reveal that the heading transition stage is also conserved in the cabbage clade. Chinese cabbage acquired through domestication a leafy head independently from the origins of heading in other cabbages; phylogenetics supports that the ancestor of all cabbages is non-heading. The launch of the transition stage is closely associated with the ambient temperature. In addition, examination of the biological activities in the transition stage identified the ethylene pathway as particularly active, and we hypothesize that this pathway was targeted for selection for domestication to form the heading trait specifically in Chinese cabbage. In conclusion, our findings on the transcriptome transition that initiated the leaf heading in Chinese cabbage and cabbage provide a new perspective for future studies of leafy head crops.
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Affiliation(s)
- Kang Zhang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Yinqing Yang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Jian Wu
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Jianli Liang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Shumin Chen
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Lei Zhang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Honghao Lv
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Xiaona Yin
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Xin Zhang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Yiyue Zhang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Lingkui Zhang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Yangyong Zhang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Michael Freeling
- Department of Plant and Microbial BiologyUniversity of California, BerkeleyBerkeleyCAUSA
| | - Xiaowu Wang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
| | - Feng Cheng
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agricultureand Rural Affairs, Sino‐Dutch Joint Laboratory of Horticultural GenomicsBeijingChina
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4
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Woodhouse MR, Sen S, Schott D, Portwood JL, Freeling M, Walley JW, Andorf CM, Schnable JC. qTeller: a tool for comparative multi-genomic gene expression analysis. Bioinformatics 2021; 38:236-242. [PMID: 34406385 DOI: 10.1093/bioinformatics/btab604] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 07/23/2021] [Accepted: 08/17/2021] [Indexed: 02/03/2023] Open
Abstract
MOTIVATION Over the last decade, RNA-Seq whole-genome sequencing has become a widely used method for measuring and understanding transcriptome-level changes in gene expression. Since RNA-Seq is relatively inexpensive, it can be used on multiple genomes to evaluate gene expression across many different conditions, tissues and cell types. Although many tools exist to map and compare RNA-Seq at the genomics level, few web-based tools are dedicated to making data generated for individual genomic analysis accessible and reusable at a gene-level scale for comparative analysis between genes, across different genomes and meta-analyses. RESULTS To address this challenge, we revamped the comparative gene expression tool qTeller to take advantage of the growing number of public RNA-Seq datasets. qTeller allows users to evaluate gene expression data in a defined genomic interval and also perform two-gene comparisons across multiple user-chosen tissues. Though previously unpublished, qTeller has been cited extensively in the scientific literature, demonstrating its importance to researchers. Our new version of qTeller now supports multiple genomes for intergenomic comparisons, and includes capabilities for both mRNA and protein abundance datasets. Other new features include support for additional data formats, modernized interface and back-end database and an optimized framework for adoption by other organisms' databases. AVAILABILITY AND IMPLEMENTATION The source code for qTeller is open-source and available through GitHub (https://github.com/Maize-Genetics-and-Genomics-Database/qTeller). A maize instance of qTeller is available at the Maize Genetics and Genomics database (MaizeGDB) (https://qteller.maizegdb.org/), where we have mapped over 200 unique datasets from GenBank across 27 maize genomes. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
| | - Shatabdi Sen
- Department of Plant Pathology & Microbiology, Iowa State University, Ames, IA 50011, USA
| | - David Schott
- Department of Computer Science, Iowa State University, Ames, IA 50011, USA
| | - John L Portwood
- USDA-ARS, Corn Insects and Crop Genetics Research Unit, Ames, IA 50011, USA
| | - Michael Freeling
- Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Justin W Walley
- Department of Plant Pathology & Microbiology, Iowa State University, Ames, IA 50011, USA
| | - Carson M Andorf
- USDA-ARS, Corn Insects and Crop Genetics Research Unit, Ames, IA 50011, USA.,Department of Computer Science, Iowa State University, Ames, IA 50011, USA
| | - James C Schnable
- Center for Plant Science Innovation & Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
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5
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Cai X, Chang L, Zhang T, Chen H, Zhang L, Lin R, Liang J, Wu J, Freeling M, Wang X. Impacts of allopolyploidization and structural variation on intraspecific diversification in Brassica rapa. Genome Biol 2021; 22:166. [PMID: 34059118 PMCID: PMC8166115 DOI: 10.1186/s13059-021-02383-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/20/2021] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Despite the prevalence and recurrence of polyploidization in the speciation of flowering plants, its impacts on crop intraspecific genome diversification are largely unknown. Brassica rapa is a mesopolyploid species that is domesticated into many subspecies with distinctive morphotypes. RESULTS Herein, we report the consequences of the whole-genome triplication (WGT) on intraspecific diversification using a pan-genome analysis of 16 de novo assembled and two reported genomes. Among the genes that derive from WGT, 13.42% of polyploidy-derived genes accumulate more transposable elements and non-synonymous mutations than other genes during individual genome evolution. We denote such genes as being "flexible." We construct the Brassica rapa ancestral genome and observe the continuing influence of the dominant subgenome on intraspecific diversification in B. rapa. The gene flexibility is biased to the more fractionated subgenomes (MFs), in contrast to the more intact gene content of the dominant LF (least fractionated) subgenome. Furthermore, polyploidy-derived flexible syntenic genes are implicated in the response to stimulus and the phytohormone auxin; this may reflect adaptation to the environment. Using an integrated graph-based genome, we investigate the structural variation (SV) landscapes in 524 B. rapa genomes. We observe that SVs track morphotype domestication. Four out of 266 candidate genes for Chinese cabbage domestication are speculated to be involved in the leafy head formation. CONCLUSIONS This pan-genome uncovers the possible contributions of allopolyploidization on intraspecific diversification and the possible and underexplored role of SVs in favorable trait domestication. Collectively, our work serves as a rich resource for genome-based B. rapa improvement.
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Affiliation(s)
- Xu Cai
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China
| | - Lichun Chang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China
| | - Tingting Zhang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China
| | - Haixu Chen
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China
| | - Lei Zhang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China
| | - Runmao Lin
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China
| | - Jianli Liang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China
| | - Jian Wu
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Xiaowu Wang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, No.12, Haidian District, Beijing, 100081, China.
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6
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Hao Y, Mabry ME, Edger PP, Freeling M, Zheng C, Jin L, VanBuren R, Colle M, An H, Abrahams RS, Washburn JD, Qi X, Barry K, Daum C, Shu S, Schmutz J, Sankoff D, Barker MS, Lyons E, Pires JC, Conant GC. The contributions from the progenitor genomes of the mesopolyploid Brassiceae are evolutionarily distinct but functionally compatible. Genome Res 2021; 31:799-810. [PMID: 33863805 PMCID: PMC8092008 DOI: 10.1101/gr.270033.120] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 03/05/2021] [Indexed: 01/08/2023]
Abstract
The members of the tribe Brassiceae share a whole-genome triplication (WGT), and one proposed model for its formation is a two-step pair of hybridizations producing hexaploid descendants. However, evidence for this model is incomplete, and the evolutionary and functional constraints that drove evolution after the hexaploidy are even less understood. Here, we report a new genome sequence of Crambe hispanica, a species sister to most sequenced Brassiceae. Using this new genome and three others that share the hexaploidy, we traced the history of gene loss after the WGT using the Polyploidy Orthology Inference Tool (POInT). We confirm the two-step formation model and infer that there was a significant temporal gap between those two allopolyploidizations, with about a third of the gene losses from the first two subgenomes occurring before the arrival of the third. We also, for the 90,000 individual genes in our study, make parental subgenome assignments, inferring, with measured uncertainty, from which of the progenitor genomes of the allohexaploidy each gene derives. We further show that each subgenome has a statistically distinguishable rate of homoeolog losses. There is little indication of functional distinction between the three subgenomes: the individual subgenomes show no patterns of functional enrichment, no excess of shared protein-protein or metabolic interactions between their members, and no biases in their likelihood of having experienced a recent selective sweep. We propose a "mix and match" model of allopolyploidy, in which subgenome origin drives homoeolog loss propensities but where genes from different subgenomes function together without difficulty.
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Affiliation(s)
- Yue Hao
- Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Makenzie E Mabry
- Division of Biological Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA
| | - Patrick P Edger
- Department of Horticulture, Michigan State University, East Lansing, Michigan 48824, USA
- Genetics and Genome Sciences, Michigan State University, East Lansing, Michigan 48824, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA
| | - Chunfang Zheng
- Department of Mathematics and Statistics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Lingling Jin
- Department of Computer Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
| | - Robert VanBuren
- Department of Horticulture, Michigan State University, East Lansing, Michigan 48824, USA
- Plant Resilience Institute, Michigan State University, East Lansing, Michigan 48824, USA
| | - Marivi Colle
- Department of Horticulture, Michigan State University, East Lansing, Michigan 48824, USA
| | - Hong An
- Division of Biological Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA
| | - R Shawn Abrahams
- Division of Biological Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA
| | - Jacob D Washburn
- Plant Genetics Research Unit, USDA-ARS, Columbia, Missouri 65211, USA
| | - Xinshuai Qi
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA
| | - Kerrie Barry
- Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Christopher Daum
- Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Shengqiang Shu
- Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jeremy Schmutz
- Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- HudsonAlpha Institute for Biotechnology, Huntsville, Alabama 35806, USA
| | - David Sankoff
- Department of Mathematics and Statistics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Michael S Barker
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA
| | - Eric Lyons
- School of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA
- BIO5 Institute, University of Arizona, Tucson, Arizona 85721, USA
| | - J Chris Pires
- Division of Biological Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA
- Informatics Institute, University of Missouri-Columbia, Columbia, Missouri 65211, USA
| | - Gavin C Conant
- Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina 27695, USA
- Program in Genetics, North Carolina State University, Raleigh, North Carolina 27695, USA
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27695, USA
- Division of Animal Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA
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7
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Abstract
Recent pangenome studies have revealed a large fraction of the gene content within a species exhibits presence-absence variation (PAV). However, coding regions alone provide an incomplete assessment of functional genomic sequence variation at the species level. Little to no attention has been paid to noncoding regulatory regions in pangenome studies, though these sequences directly modulate gene expression and phenotype. To uncover regulatory genetic variation, we generated chromosome-scale genome assemblies for thirty Arabidopsis thaliana accessions from multiple distinct habitats and characterized species level variation in Conserved Noncoding Sequences (CNS). Our analyses uncovered not only PAV and positional variation (PosV) but that diversity in CNS is nonrandom, with variants shared across different accessions. Using evolutionary analyses and chromatin accessibility data, we provide further evidence supporting roles for conserved and variable CNS in gene regulation. Additionally, our data suggests that transposable elements contribute to CNS variation. Characterizing species-level diversity in all functional genomic sequences may later uncover previously unknown mechanistic links between genotype and phenotype.
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Affiliation(s)
- Alan E Yocca
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA.,Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Zefu Lu
- Department of Genetics, University of Georgia, Athens, GA, USA
| | | | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Patrick P Edger
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA
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8
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Edger PP, Poorten TJ, VanBuren R, Hardigan MA, Colle M, McKain MR, Smith RD, Teresi SJ, Nelson ADL, Wai CM, Alger EI, Bird KA, Yocca AE, Pumplin N, Ou S, Ben-Zvi G, Brodt A, Baruch K, Swale T, Shiue L, Acharya CB, Cole GS, Mower JP, Childs KL, Jiang N, Lyons E, Freeling M, Puzey JR, Knapp SJ. Author Correction: Origin and evolution of the octoploid strawberry genome. Nat Genet 2019; 51:765. [PMID: 30842601 PMCID: PMC7608257 DOI: 10.1038/s41588-019-0380-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Patrick P Edger
- Department of Horticulture, Michigan State University, East Lansing, MI, USA. .,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA.
| | - Thomas J Poorten
- Department of Plant Sciences, University of California-Davis, Davis, CA, USA
| | - Robert VanBuren
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Plant Resilience Institute, Michigan State University, East Lansing, MI, USA
| | - Michael A Hardigan
- Department of Plant Sciences, University of California-Davis, Davis, CA, USA
| | - Marivi Colle
- Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Michael R McKain
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, USA
| | - Ronald D Smith
- Department of Biology, College of William and Mary, Williamsburg, VA, USA
| | - Scott J Teresi
- Department of Biology, College of William and Mary, Williamsburg, VA, USA
| | | | - Ching Man Wai
- Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Elizabeth I Alger
- Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Kevin A Bird
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA
| | - Alan E Yocca
- Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Nathan Pumplin
- Department of Plant Sciences, University of California-Davis, Davis, CA, USA
| | - Shujun Ou
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA
| | | | | | | | | | | | - Charlotte B Acharya
- Department of Plant Sciences, University of California-Davis, Davis, CA, USA
| | - Glenn S Cole
- Department of Plant Sciences, University of California-Davis, Davis, CA, USA
| | - Jeffrey P Mower
- Center for Plant Science Innovation, University of Nebraska, Lincoln, NE, USA
| | - Kevin L Childs
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA.,Center for Genomics Enabled Plant Science, Michigan State University, East Lansing, MI, USA
| | - Ning Jiang
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA
| | - Eric Lyons
- School of Plant Sciences, University of Arizona, Tucson, AZ, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Joshua R Puzey
- School of Plant Sciences, University of Arizona, Tucson, AZ, USA
| | - Steven J Knapp
- Department of Plant Sciences, University of California-Davis, Davis, CA, USA.
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9
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Edger PP, Poorten TJ, VanBuren R, Hardigan MA, Colle M, McKain MR, Smith RD, Teresi SJ, Nelson ADL, Wai CM, Alger EI, Bird KA, Yocca AE, Pumplin N, Ou S, Ben-Zvi G, Brodt A, Baruch K, Swale T, Shiue L, Acharya CB, Cole GS, Mower JP, Childs KL, Jiang N, Lyons E, Freeling M, Puzey JR, Knapp SJ. Origin and evolution of the octoploid strawberry genome. Nat Genet 2019; 51:541-547. [PMID: 30804557 PMCID: PMC6882729 DOI: 10.1038/s41588-019-0356-4] [Citation(s) in RCA: 304] [Impact Index Per Article: 60.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 01/15/2019] [Indexed: 01/19/2023]
Abstract
Cultivated strawberry emerged from the hybridization of two wild octoploid species, both descendants from the merger of four diploid progenitor species into a single nucleus more than 1 million years ago. Here we report a near-complete chromosome-scale assembly for cultivated octoploid strawberry (Fragaria × ananassa) and uncovered the origin and evolutionary processes that shaped this complex allopolyploid. We identified the extant relatives of each diploid progenitor species and provide support for the North American origin of octoploid strawberry. We examined the dynamics among the four subgenomes in octoploid strawberry and uncovered the presence of a single dominant subgenome with significantly greater gene content, gene expression abundance, and biased exchanges between homoeologous chromosomes, as compared with the other subgenomes. Pathway analysis showed that certain metabolomic and disease-resistance traits are largely controlled by the dominant subgenome. These findings and the reference genome should serve as a powerful platform for future evolutionary studies and enable molecular breeding in strawberry. Chromosome-scale assembly for the cultivated octoploid strawberry (Fragaria × ananassa) uncovers the origin and evolutionary processes that shaped this complex allopolyploid, providing a useful resource for genome-wide analyses and molecular breeding.
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Affiliation(s)
- Patrick P Edger
- Department of Horticulture, Michigan State University, East Lansing, MI, USA. .,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA.
| | - Thomas J Poorten
- Department of Plant Sciences, University of California-Davis, Davis, California, USA
| | - Robert VanBuren
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Plant Resilience Institute, Michigan State University, East Lansing, MI, USA
| | - Michael A Hardigan
- Department of Plant Sciences, University of California-Davis, Davis, California, USA
| | - Marivi Colle
- Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Michael R McKain
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, USA
| | - Ronald D Smith
- Department of Biology, College of William and Mary, Williamsburg, VA, USA
| | - Scott J Teresi
- Department of Biology, College of William and Mary, Williamsburg, VA, USA
| | | | - Ching Man Wai
- Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Elizabeth I Alger
- Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Kevin A Bird
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA
| | - Alan E Yocca
- Department of Horticulture, Michigan State University, East Lansing, MI, USA
| | - Nathan Pumplin
- Department of Plant Sciences, University of California-Davis, Davis, California, USA
| | - Shujun Ou
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA
| | | | | | | | | | | | - Charlotte B Acharya
- Department of Plant Sciences, University of California-Davis, Davis, California, USA
| | - Glenn S Cole
- Department of Plant Sciences, University of California-Davis, Davis, California, USA
| | - Jeffrey P Mower
- Center for Plant Science Innovation, University of Nebraska, Lincoln, NE, USA
| | - Kevin L Childs
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA.,Center for Genomics Enabled Plant Science, Michigan State University, East Lansing, MI, USA
| | - Ning Jiang
- Department of Horticulture, Michigan State University, East Lansing, MI, USA.,Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, USA
| | - Eric Lyons
- School of Plant Sciences, University of Arizona, Tucson, AZ, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Joshua R Puzey
- Department of Biology, College of William and Mary, Williamsburg, VA, USA
| | - Steven J Knapp
- Department of Plant Sciences, University of California-Davis, Davis, California, USA.
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10
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Reiser L, Harper L, Freeling M, Han B, Luan S. FAIR: A Call to Make Published Data More Findable, Accessible, Interoperable, and Reusable. Mol Plant 2018; 11:1105-1108. [PMID: 30076986 DOI: 10.1016/j.molp.2018.07.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 07/25/2018] [Accepted: 07/30/2018] [Indexed: 06/08/2023]
Affiliation(s)
- Leonore Reiser
- The Arabidopsis Information Resource/Phoenix Bioinformatics, Fremont, CA 94538, USA.
| | - Lisa Harper
- Maize Genome Database/United States Department of Agriculture, Albany, CA 94710, USA.
| | - Michael Freeling
- Department of Plant Biology, University of California, Berkeley, CA 94720, USA
| | - Bin Han
- National Center for Gene Research, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200233, China
| | - Sheng Luan
- Department of Plant Biology, University of California, Berkeley, CA 94720, USA
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11
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Cheng F, Wu J, Cai X, Liang J, Freeling M, Wang X. Gene retention, fractionation and subgenome differences in polyploid plants. Nat Plants 2018; 4:258-268. [PMID: 29725103 DOI: 10.1038/s41477-018-0136-7] [Citation(s) in RCA: 170] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 03/20/2018] [Indexed: 05/22/2023]
Abstract
All natural plant species are evolved from ancient polyploids. Polyloidization plays an important role in plant genome evolution, species divergence and crop domestication. We review how the pattern of polyploidy within the plant phylogenetic tree has engendered hypotheses involving mass extinctions, lag-times following polyploidy, and epochs of asexuality. Polyploidization has happened repeatedly in plant evolution and, we conclude, is important for crop domestication. Once duplicated, the effect of purifying selection on any one duplicated gene is relaxed, permitting duplicate gene and regulatory element loss (fractionation). We review the general topic of fractionation, and how some gene categories are retained more than others. Several explanations, including neofunctionalization, subfunctionalization and gene product dosage balance, have been shown to influence gene content over time. For allopolyploids, genetic differences between parental lines immediately manifest as subgenome dominance in the wide-hybrid, and persist and propagate for tens of millions of years. While epigenetic modifications are certainly involved in genome dominance, it has been difficult to determine which came first, the chromatin marks being measured or gene expression. Data support the conclusion that genome dominance and heterosis are antagonistic and mechanically entangled; both happen immediately in the synthetic wide-cross hybrid. Also operating in this hybrid are mechanisms of 'paralogue interference'. We present a foundation model to explain gene expression and vigour in a wide hybrid/new allotetraploid. This Review concludes that some mechanisms operate immediately at the wide-hybrid, and other mechanisms begin their operations later. Direct interaction of new paralogous genes, as measured using high-resolution chromatin conformation capture, should inform future research and single cell transcriptome sequencing should help achieve specificity while studying gene sub- and neo-functionalization.
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Affiliation(s)
- Feng Cheng
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Sino-Dutch Joint Laboratory of Horticultural Genomics, Beijing, China
| | - Jian Wu
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Sino-Dutch Joint Laboratory of Horticultural Genomics, Beijing, China
| | - Xu Cai
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Sino-Dutch Joint Laboratory of Horticultural Genomics, Beijing, China
| | - Jianli Liang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Sino-Dutch Joint Laboratory of Horticultural Genomics, Beijing, China
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA.
| | - Xiaowu Wang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops of the Ministry of Agriculture, Sino-Dutch Joint Laboratory of Horticultural Genomics, Beijing, China.
- Shandong Provincial Key Laboratory of Protected Vegetable Molecular Breeding, Shandong Shouguang Vegetable Seed Industry Group Co. Ltd., Shandong Province, China.
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12
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Grover JW, Kendall T, Baten A, Burgess D, Freeling M, King GJ, Mosher RA. Maternal components of RNA-directed DNA methylation are required for seed development in Brassica rapa. Plant J 2018; 94:575-582. [PMID: 29569777 DOI: 10.1111/tpj.13910] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 03/10/2018] [Accepted: 03/13/2018] [Indexed: 05/20/2023]
Abstract
Small RNAs trigger repressive DNA methylation at thousands of transposable elements in a process called RNA-directed DNA methylation (RdDM). The molecular mechanism of RdDM is well characterized in Arabidopsis, yet the biological function remains unclear, as loss of RdDM in Arabidopsis causes no overt defects, even after generations of inbreeding. It is known that 24 nucleotide Pol IV-dependent siRNAs, the hallmark of RdDM, are abundant in flowers and developing seeds, indicating that RdDM might be important during reproduction. Here we show that, unlike Arabidopsis, mutations in the Pol IV-dependent small RNA pathway cause severe and specific reproductive defects in Brassica rapa. High rates of abortion occur when seeds have RdDM mutant mothers, but not when they have mutant fathers. Although abortion occurs after fertilization, RdDM function is required in maternal somatic tissue, not in the female gametophyte or the developing zygote, suggesting that siRNAs from the maternal soma might function in filial tissues. We propose that recently outbreeding species such as B. rapa are key to understanding the role of RdDM during plant reproduction.
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Affiliation(s)
- Jeffrey W Grover
- Department of Molecular & Cellular Biology, The University of Arizona, Tucson, AZ, 85721, USA
| | - Timmy Kendall
- The School of Plant Sciences, The University of Arizona, Tucson, AZ, 85721, USA
| | - Abdul Baten
- Southern Cross Plant Science, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Diane Burgess
- Department of Plant and Microbial Biology, The University of California, Berkeley, CA, 94720, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, The University of California, Berkeley, CA, 94720, USA
| | - Graham J King
- Southern Cross Plant Science, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Rebecca A Mosher
- Department of Molecular & Cellular Biology, The University of Arizona, Tucson, AZ, 85721, USA
- The School of Plant Sciences, The University of Arizona, Tucson, AZ, 85721, USA
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13
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Grover JW, Kendall T, Baten A, Burgess D, Freeling M, King GJ, Mosher RA. Maternal components of RNA-directed DNA methylation are required for seed development in Brassica rapa. Plant J 2018; 94:573-574. [PMID: 29569777 DOI: 10.1111/tpj.13935] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 03/10/2018] [Accepted: 03/13/2018] [Indexed: 05/24/2023]
Abstract
Small RNAs trigger repressive DNA methylation at thousands of transposable elements in a process called RNA-directed DNA methylation (RdDM). The molecular mechanism of RdDM is well characterized in Arabidopsis, yet the biological function remains unclear, as loss of RdDM in Arabidopsis causes no overt defects, even after generations of inbreeding. It is known that 24 nucleotide Pol IV-dependent siRNAs, the hallmark of RdDM, are abundant in flowers and developing seeds, indicating that RdDM might be important during reproduction. Here we show that, unlike Arabidopsis, mutations in the Pol IV-dependent small RNA pathway cause severe and specific reproductive defects in Brassica rapa. High rates of abortion occur when seeds have RdDM mutant mothers, but not when they have mutant fathers. Although abortion occurs after fertilization, RdDM function is required in maternal somatic tissue, not in the female gametophyte or the developing zygote, suggesting that siRNAs from the maternal soma might function in filial tissues. We propose that recently outbreeding species such as B. rapa are key to understanding the role of RdDM during plant reproduction.
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Affiliation(s)
- Jeffrey W Grover
- Department of Molecular & Cellular Biology, The University of Arizona, Tucson, AZ, 85721, USA
| | - Timmy Kendall
- The School of Plant Sciences, The University of Arizona, Tucson, AZ, 85721, USA
| | - Abdul Baten
- Southern Cross Plant Science, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Diane Burgess
- Department of Plant and Microbial Biology, The University of California, Berkeley, CA, 94720, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, The University of California, Berkeley, CA, 94720, USA
| | - Graham J King
- Southern Cross Plant Science, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Rebecca A Mosher
- Department of Molecular & Cellular Biology, The University of Arizona, Tucson, AZ, 85721, USA
- The School of Plant Sciences, The University of Arizona, Tucson, AZ, 85721, USA
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14
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Freeling M. Picking up the Ball at the K/Pg Boundary: The Distribution of Ancient Polyploidies in the Plant Phylogenetic Tree as a Spandrel of Asexuality with Occasional Sex. Plant Cell 2017; 29:202-206. [PMID: 28213362 PMCID: PMC5354197 DOI: 10.1105/tpc.16.00836] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/05/2017] [Accepted: 02/15/2017] [Indexed: 05/23/2023]
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15
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Cheng F, Sun C, Wu J, Schnable J, Woodhouse MR, Liang J, Cai C, Freeling M, Wang X. Epigenetic regulation of subgenome dominance following whole genome triplication in Brassica rapa. New Phytol 2016; 211:288-99. [PMID: 26871271 DOI: 10.1111/nph.13884] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 12/28/2015] [Indexed: 05/10/2023]
Abstract
Subgenome dominance is an important phenomenon observed in allopolyploids after whole genome duplication, in which one subgenome retains more genes as well as contributes more to the higher expressing gene copy of paralogous genes. To dissect the mechanism of subgenome dominance, we systematically investigated the relationships of gene expression, transposable element (TE) distribution and small RNA targeting, relating to the multicopy paralogous genes generated from whole genome triplication in Brassica rapa. The subgenome dominance was found to be regulated by a relatively stable factor established previously, then inherited by and shared among B. rapa varieties. In addition, we found a biased distribution of TEs between flanking regions of paralogous genes. Furthermore, the 24-nt small RNAs target TEs and are negatively correlated to the dominant expression of individual paralogous gene pairs. The biased distribution of TEs among subgenomes and the targeting of 24-nt small RNAs together produce the dominant expression phenomenon at a subgenome scale. Based on these findings, we propose a bucket hypothesis to illustrate subgenome dominance and hybrid vigor. Our findings and hypothesis are valuable for the evolutionary study of polyploids, and may shed light on studies of hybrid vigor, which is common to most species.
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Affiliation(s)
- Feng Cheng
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Chao Sun
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Jian Wu
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - James Schnable
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, 68588, USA
| | - Margaret R Woodhouse
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Jianli Liang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Chengcheng Cai
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Xiaowu Wang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
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16
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Freeling M, Scanlon MJ, Fowler JE. Fractionation and subfunctionalization following genome duplications: mechanisms that drive gene content and their consequences. Curr Opin Genet Dev 2015; 35:110-8. [PMID: 26657818 DOI: 10.1016/j.gde.2015.11.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 11/09/2015] [Accepted: 11/09/2015] [Indexed: 12/11/2022]
Abstract
A gene's duplication relaxes selection. Loss of duplicate, low-function DNA (fractionation) sometimes follows, mostly by deletion in plants, but mostly via the pseudogene pathway in fish and other clades with smaller population sizes. Subfunctionalization--the founding term of the Xfunctionalization lexicon--while not the general cause of differences in duplicate gene retention, becomes primary as the number of a gene's cis-regulatory sites increases. Balanced gene drive explains retention for the average gene. Both maintenance-of-balance and subfunctionalization drive gene content nonrandomly, and currently fall outside of our accepted Theory of Evolution. The 'typical' mutation encountered by a gene duplicate is not a neutral loss-of-function; dominant mutations (Muller's lexicon; these are not neutral) abound, and confound X functionalization terms like 'neofunctionalization'. Confusion of words may cause confusion of thought. As with many plants, fish tetraploidies provide a higher throughput surrogate-genetic method to infer function from human and other vertebrate ENCODE-like regulatory sites.
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Affiliation(s)
- Michael Freeling
- Department of Plant and Microbial Biology, Univ. California, Berkeley, CA 94720, United States.
| | - Michael J Scanlon
- Section of Plant Biology, Cornell University, Ithaca, NY 14853, United States
| | - John E Fowler
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, United States
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17
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Ming R, VanBuren R, Wai CM, Tang H, Schatz MC, Bowers JE, Lyons E, Wang ML, Chen J, Biggers E, Zhang J, Huang L, Zhang L, Miao W, Zhang J, Ye Z, Miao C, Lin Z, Wang H, Zhou H, Yim WC, Priest HD, Zheng C, Woodhouse M, Edger PP, Guyot R, Guo HB, Guo H, Zheng G, Singh R, Sharma A, Min X, Zheng Y, Lee H, Gurtowski J, Sedlazeck FJ, Harkess A, McKain MR, Liao Z, Fang J, Liu J, Zhang X, Zhang Q, Hu W, Qin Y, Wang K, Chen LY, Shirley N, Lin YR, Liu LY, Hernandez AG, Wright CL, Bulone V, Tuskan GA, Heath K, Zee F, Moore PH, Sunkar R, Leebens-Mack JH, Mockler T, Bennetzen JL, Freeling M, Sankoff D, Paterson AH, Zhu X, Yang X, Smith JAC, Cushman JC, Paull RE, Yu Q. The pineapple genome and the evolution of CAM photosynthesis. Nat Genet 2015; 47:1435-42. [PMID: 26523774 PMCID: PMC4867222 DOI: 10.1038/ng.3435] [Citation(s) in RCA: 301] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 10/05/2015] [Indexed: 12/21/2022]
Abstract
Pineapple (Ananas comosus (L.) Merr.) is the most economically valuable crop possessing crassulacean acid metabolism (CAM), a photosynthetic carbon assimilation pathway with high water-use efficiency, and the second most important tropical fruit. We sequenced the genomes of pineapple varieties F153 and MD2 and a wild pineapple relative, Ananas bracteatus accession CB5. The pineapple genome has one fewer ancient whole-genome duplication event than sequenced grass genomes and a conserved karyotype with seven chromosomes from before the ρ duplication event. The pineapple lineage has transitioned from C3 photosynthesis to CAM, with CAM-related genes exhibiting a diel expression pattern in photosynthetic tissues. CAM pathway genes were enriched with cis-regulatory elements associated with the regulation of circadian clock genes, providing the first cis-regulatory link between CAM and circadian clock regulation. Pineapple CAM photosynthesis evolved by the reconfiguration of pathways in C3 plants, through the regulatory neofunctionalization of preexisting genes and not through the acquisition of neofunctionalized genes via whole-genome or tandem gene duplication.
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Affiliation(s)
- Ray Ming
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Robert VanBuren
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Donald Danforth Plant Science Center, St. Louis, MO, USA
| | - Ching Man Wai
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Haibao Tang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
- iPlant Collaborative/University of Arizona, Tuscon, AZ 85719, USA
| | | | - John E. Bowers
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Eric Lyons
- iPlant Collaborative/University of Arizona, Tuscon, AZ 85719, USA
| | - Ming-Li Wang
- Hawaii Agriculture Research Center, Kunia, HI 96759, USA
| | - Jung Chen
- Department of Tropical Plant and Soil Sciences, University of Hawaii, Honolulu, HI 96822, USA
| | - Eric Biggers
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY11724, USA
| | - Jisen Zhang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Lixian Huang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Lingmao Zhang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Wenjing Miao
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Jian Zhang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Zhangyao Ye
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Chenyong Miao
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Zhicong Lin
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Hao Wang
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Hongye Zhou
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Won C. Yim
- Department of Biochemistry and Molecular Biology, MS330, University of Nevada, Reno, NV 89557-0330, USA
| | | | - Chunfang Zheng
- Department of Mathematics and Statistics, University of Ottawa, Ottawa, Canada K1N 6N5
| | - Margaret Woodhouse
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
| | - Patrick P. Edger
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
| | - Romain Guyot
- IRD, UMR DIADE, EVODYN, BP 64501, 34394 Montpellier Cedex 5, France
| | - Hao-Bo Guo
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Hong Guo
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Guangyong Zheng
- Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Ratnesh Singh
- Texas A&M AgriLife Research, Department of Plant Pathology & Microbiology, Texas A&M University System, Dallas, TX 75252, USA
| | - Anupma Sharma
- Texas A&M AgriLife Research, Department of Plant Pathology & Microbiology, Texas A&M University System, Dallas, TX 75252, USA
| | - Xiangjia Min
- Department of Biological Sciences, Youngstown State University, Youngstown, OH 44555, USA
| | - Yun Zheng
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
| | - Hayan Lee
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY11724, USA
| | - James Gurtowski
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY11724, USA
| | | | - Alex Harkess
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | | | - Zhenyang Liao
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Jingping Fang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Juan Liu
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Xiaodan Zhang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Qing Zhang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Weichang Hu
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Yuan Qin
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Kai Wang
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Li-Yu Chen
- FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China
| | - Neil Shirley
- ARC Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Waite Campus Urrbrae, South Australia 5064, Australia
| | - Yann-Rong Lin
- Department of Agronomy, National Taiwan University, Taipei 10617, Taiwan
| | - Li-Yu Liu
- Department of Agronomy, National Taiwan University, Taipei 10617, Taiwan
| | - Alvaro G. Hernandez
- W.M. Keck Center, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Chris L. Wright
- W.M. Keck Center, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Vincent Bulone
- ARC Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Waite Campus Urrbrae, South Australia 5064, Australia
| | - Gerald A. Tuskan
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Katy Heath
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Francis Zee
- USDA-ARS, Pacific Basin Agricultural Research Center, Hilo, HI 96720, USA
| | - Paul H. Moore
- Hawaii Agriculture Research Center, Kunia, HI 96759, USA
| | - Ramanjulu Sunkar
- Department of Biochemistry and Molecular Biology, 246 Noble Research Center, Oklahoma State University, Stillwater, OK 74078, USA
| | | | - Todd Mockler
- Donald Danforth Plant Science Center, St. Louis, MO, USA
| | | | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
| | - David Sankoff
- Department of Mathematics and Statistics, University of Ottawa, Ottawa, Canada K1N 6N5
| | - Andrew H. Paterson
- Plant Genome Mapping Laboratory, University of Georgia, Athens, GA 30602, USA
| | - Xinguang Zhu
- Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiaohan Yang
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - J. Andrew C. Smith
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - John C. Cushman
- Department of Biochemistry and Molecular Biology, MS330, University of Nevada, Reno, NV 89557-0330, USA
| | - Robert E. Paull
- Department of Tropical Plant and Soil Sciences, University of Hawaii, Honolulu, HI 96822, USA
| | - Qingyi Yu
- Texas A&M AgriLife Research, Department of Plant Pathology & Microbiology, Texas A&M University System, Dallas, TX 75252, USA
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18
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VanBuren R, Bryant D, Edger PP, Tang H, Burgess D, Challabathula D, Spittle K, Hall R, Gu J, Lyons E, Freeling M, Bartels D, Ten Hallers B, Hastie A, Michael TP, Mockler TC. Single-molecule sequencing of the desiccation-tolerant grass Oropetium thomaeum. Nature 2015; 527:508-11. [PMID: 26560029 DOI: 10.1038/nature15714] [Citation(s) in RCA: 233] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 09/10/2015] [Indexed: 12/20/2022]
Abstract
Plant genomes, and eukaryotic genomes in general, are typically repetitive, polyploid and heterozygous, which complicates genome assembly. The short read lengths of early Sanger and current next-generation sequencing platforms hinder assembly through complex repeat regions, and many draft and reference genomes are fragmented, lacking skewed GC and repetitive intergenic sequences, which are gaining importance due to projects like the Encyclopedia of DNA Elements (ENCODE). Here we report the whole-genome sequencing and assembly of the desiccation-tolerant grass Oropetium thomaeum. Using only single-molecule real-time sequencing, which generates long (>16 kilobases) reads with random errors, we assembled 99% (244 megabases) of the Oropetium genome into 625 contigs with an N50 length of 2.4 megabases. Oropetium is an example of a 'near-complete' draft genome which includes gapless coverage over gene space as well as intergenic sequences such as centromeres, telomeres, transposable elements and rRNA clusters that are typically unassembled in draft genomes. Oropetium has 28,466 protein-coding genes and 43% repeat sequences, yet with 30% more compact euchromatic regions it is the smallest known grass genome. The Oropetium genome demonstrates the utility of single-molecule real-time sequencing for assembling high-quality plant and other eukaryotic genomes, and serves as a valuable resource for the plant comparative genomics community.
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Affiliation(s)
- Robert VanBuren
- Donald Danforth Plant Science Center, St Louis, Missouri 63132, USA
| | - Doug Bryant
- Donald Danforth Plant Science Center, St Louis, Missouri 63132, USA
| | - Patrick P Edger
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720, USA.,Department of Horticulture, Michigan State University, East Lansing, Michigan 48823, USA
| | - Haibao Tang
- iPlant Collaborative, School of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.,Center for Genomics and Biotechnology, Haixia Institute of Science and Technology (HIST), Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Diane Burgess
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720, USA
| | | | | | - Richard Hall
- Pacific Biosciences, Menlo Park, California 94025, USA
| | - Jenny Gu
- Pacific Biosciences, Menlo Park, California 94025, USA
| | - Eric Lyons
- iPlant Collaborative, School of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720, USA
| | | | | | - Alex Hastie
- BioNano Genomics, San Diego, California 92121, USA
| | | | - Todd C Mockler
- Donald Danforth Plant Science Center, St Louis, Missouri 63132, USA
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19
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Burgess DG, Xu J, Freeling M. Advances in understanding cis regulation of the plant gene with an emphasis on comparative genomics. Curr Opin Plant Biol 2015; 27:141-7. [PMID: 26247124 DOI: 10.1016/j.pbi.2015.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 06/26/2015] [Accepted: 07/07/2015] [Indexed: 05/07/2023]
Abstract
The plant gene model remains largely an extrapolation from animals, with the cis functional unit, the gene, cast as a dynamic looping structure. Molecular genetics with model plants continues to make advances; highlighted here are quantitative-occupancy results from the Arabidopsis thaliana (Arabidopsis) Phytochrome-Interacting bHLH transcription Factors (PIF) quartet. Compared to this complex snapshot, results from chromatin occupancy and other Encyclopedia of DNA Elements (ENCODE)-like approaches increase our transcription factor-motif cognate library, but regulation cannot by itself be inferred from binding. Complementary published Arabidopsis conserved noncoding sequence lists are compared, evaluated, merged, and released. Comparative genomic approaches have identified a cis modifier of a gene's expression-hypothetically, a transposon-based 'rheostat'-that works in all cells, times and places.
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Affiliation(s)
- Diane G Burgess
- Department of Plant and Microbial Biology, University of California, Berkeley 94720, United States.
| | - Jie Xu
- Maize Research Institute, Sichuan Agricultural University, Wenjiang, Sichuan 611130, China
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley 94720, United States
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20
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Freeling M, Xu J, Woodhouse M, Lisch D. A Solution to the C-Value Paradox and the Function of Junk DNA: The Genome Balance Hypothesis. Mol Plant 2015; 8:899-910. [PMID: 25743198 DOI: 10.1016/j.molp.2015.02.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 02/03/2015] [Accepted: 02/18/2015] [Indexed: 05/11/2023]
Abstract
The Genome Balance Hypothesis originated from a recent study that provided a mechanism for the phenomenon of genome dominance in ancient polyploids: unique 24nt RNA coverage near genes is greater in genes on the recessive subgenome irrespective of differences in gene expression. 24nt RNAs target transposons. Transposon position effects are now hypothesized to balance the expression of networked genes and provide spring-like tension between pericentromeric heterochromatin and microtubules. The balance (coordination) of gene expression and centromere movement is under selection. Our hypothesis states that this balance can be maintained by many or few transposons about equally well. We explain known balanced distributions of junk DNA within genomes and between subgenomes in allopolyploids (and our hypothesis passes "the onion test" for any so-called solution to the C-value paradox). Importantly, when the allotetraploid maize chromosomes delete redundant genes, their nearby transposons are also lost; this result is explained if transposons near genes function. The Genome Balance Hypothesis is hypothetical because the position effect mechanisms implicated are not proved to apply to all junk DNA, and the continuous nature of the centromeric and gene position effects have not yet been studied as a single phenomenon.
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Affiliation(s)
- Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
| | - Jie Xu
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA; Maize Research Institute, Sichuan Agricultural University, Wenjiang, Sichuan 611130, China
| | - Margaret Woodhouse
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
| | - Damon Lisch
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA
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21
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de Almeida AMR, Yockteng R, Schnable J, Alvarez-Buylla ER, Freeling M, Specht CD. Co-option of the polarity gene network shapes filament morphology in angiosperms. Sci Rep 2014; 4:6194. [PMID: 25168962 PMCID: PMC5385836 DOI: 10.1038/srep06194] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 07/29/2014] [Indexed: 11/09/2022] Open
Abstract
The molecular genetic mechanisms underlying abaxial-adaxial polarity in plants have been studied as a property of lateral and flattened organs, such as leaves. In leaves, laminar expansion occurs as a result of balanced abaxial-adaxial gene expression. Over- or under- expression of either abaxializing or adaxializing genes inhibits laminar growth, resulting in a mutant radialized phenotype. Here, we show that co-option of the abaxial-adaxial polarity gene network plays a role in the evolution of stamen filament morphology in angiosperms. RNA-Seq data from species bearing laminar (flattened) or radial (cylindrical) filaments demonstrates that species with laminar filaments exhibit balanced expression of abaxial-adaxial (ab-ad) genes, while overexpression of a YABBY gene is found in species with radial filaments. This result suggests that unbalanced expression of ab-ad genes results in inhibition of laminar outgrowth, leading to a radially symmetric structure as found in many angiosperm filaments. We anticipate that co-option of the polarity gene network is a fundamental mechanism shaping many aspects of plant morphology during angiosperm evolution.
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Affiliation(s)
| | - Roxana Yockteng
- 1] Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720 USA [2] Institut de Systématique, Evolution et Biodiversité (UMR 7205 CNRS, Muséum National d'Histoire Naturelle, CP39, 16 rue Buffon, 75231 Paris Cedex 05, France
| | - James Schnable
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720 USA
| | - Elena R Alvarez-Buylla
- 1] Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720 USA [2] Laboratorio de Genética, Epigenética, Desarrollo y Evolución de Plantas, Instituto de Ecología, Universidad Nacional Autónoma de México, Ciudad Universitaria, 3er Circuito Exterior Junto a Jardín Botánico, Coyoacán, México DF 04510
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720 USA
| | - Chelsea D Specht
- 1] Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720 USA [2] Department of Integrative Biology and The University and Jepson Herbaria, University of California, Berkeley, CA 94720 USA
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22
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Burgess D, Freeling M. The most deeply conserved noncoding sequences in plants serve similar functions to those in vertebrates despite large differences in evolutionary rates. Plant Cell 2014; 26:946-61. [PMID: 24681619 PMCID: PMC4001403 DOI: 10.1105/tpc.113.121905] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
In vertebrates, conserved noncoding elements (CNEs) are functionally constrained sequences that can show striking conservation over >400 million years of evolutionary distance and frequently are located megabases away from target developmental genes. Conserved noncoding sequences (CNSs) in plants are much shorter, and it has been difficult to detect conservation among distantly related genomes. In this article, we show not only that CNS sequences can be detected throughout the eudicot clade of flowering plants, but also that a subset of 37 CNSs can be found in all flowering plants (diverging ∼170 million years ago). These CNSs are functionally similar to vertebrate CNEs, being highly associated with transcription factor and development genes and enriched in transcription factor binding sites. Some of the most highly conserved sequences occur in genes encoding RNA binding proteins, particularly the RNA splicing-associated SR genes. Differences in sequence conservation between plants and animals are likely to reflect differences in the biology of the organisms, with plants being much more able to tolerate genomic deletions and whole-genome duplication events due, in part, to their far greater fecundity compared with vertebrates.
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23
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Bolduc N, Tyers RG, Freeling M, Hake S. Unequal redundancy in maize knotted1 homeobox genes. Plant Physiol 2014; 164:229-38. [PMID: 24218490 PMCID: PMC3875803 DOI: 10.1104/pp.113.228791] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 11/08/2013] [Indexed: 05/24/2023]
Abstract
The knotted1 (kn1) homeobox (knox) gene family was first identified through gain-of-function dominant mutants in maize (Zea mays). Class I knox members are expressed in meristems but excluded from leaves. In maize, a loss-of-function phenotype has only been characterized for kn1. To assess the function of another knox member, we characterized a loss-of-function mutation of rough sheath1 (rs1). rs1-mum1 has no phenotype alone but exacerbates several aspects of the kn1 phenotype. In permissive backgrounds in which kn1 mutants grow to maturity, loss of a single copy of rs1 enhances the tassel branch reduction phenotype, while loss of both copies results in limited shoots. In less introgressed lines, double mutants can grow to maturity but are shorter. Using a KNOX antibody, we demonstrate that RS1 binds in vivo to some of the KN1 target genes, which could partially explain why KN1 binds many genes but modulates few. Our results demonstrate an unequal redundancy between knox genes, with a role for rs1 only revealed in the complete absence of kn1.
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24
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Abstract
Whole genome duplications (WGDs) occurred in the distant evolutionary history of many lineages and are particularly frequent in the flowering plant lineages. Following paleopolyploidization in plants, most duplicated genes are deleted by intrachromosomal recombination, a process referred to as fractionation. In the examples studied so far, genes are disproportionately lost from one of the parental subgenomes (biased fractionation) and the subgenome having lost the lowest number of genes is more expressed (genome dominance). In the present study, we analyzed the pattern of gene deletion and gene expression following the most recent WGD in banana (alpha event) and extended our analyses to seven other sequenced plant genomes: poplar, soybean, medicago, arabidopsis, sorghum, brassica, and maize. We propose a new class of ancient WGD, with Musa (alpha), poplar, and soybean as members, where genes are both deleted and expressed to an equal extent (unbiased fractionation and genome equivalence). We suggest that WGDs with genome dominance and biased fractionation (Class I) may result from ancient allotetraploidies, while WGDs without genome dominance or biased fractionation (Class II) may result from ancient autotetraploidies.
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Affiliation(s)
- Olivier Garsmeur
- Centre de Cooperation Internationale en Recherche Agronomique pour le Developpement (CIRAD), UMR AGAP, Montpellier, France
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25
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Subramaniam S, Wang X, Freeling M, Pires JC. The fate of Arabidopsis thaliana homeologous CNSs and their motifs in the Paleohexaploid Brassica rapa. Genome Biol Evol 2013; 5:646-60. [PMID: 23493633 PMCID: PMC3641636 DOI: 10.1093/gbe/evt035] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Following polyploidy, duplicate genes are often deleted, and if they are not, then duplicate regulatory regions are sometimes lost. By what mechanism is this loss and what is the chance that such a loss removes function? To explore these questions, we followed individual Arabidopsis thaliana–A. thaliana conserved noncoding sequences (CNSs) into the Brassica ancestor, through a paleohexaploidy and into Brassica rapa. Thus, a single Brassicaceae CNS has six potential orthologous positions in B. rapa; a single Arabidopsis CNS has three potential homeologous positions. We reasoned that a CNS, if present on a singlet Brassica gene, would be unlikely to lose function compared with a more redundant CNS, and this is the case. Redundant CNSs go nondetectable often. Using this logic, each mechanism of CNS loss was assigned a metric of functionality. By definition, proved deletions do not function as sequence. Our results indicated that CNSs that go nondetectable by base substitution or large insertion are almost certainly still functional (redundancy does not matter much to their detectability frequency), whereas those lost by inferred deletion or indels are approximately 75% likely to be nonfunctional. Overall, an average nondetectable, once-redundant CNS more than 30 bp in length has a 72% chance of being nonfunctional, and that makes sense because 97% of them sort to a molecular mechanism with “deletion” in its description, but base substitutions do cause loss. Similarly, proved-functional G-boxes go undetectable by deletion 82% of the time. Fractionation mutagenesis is a procedure that uses polyploidy as a mutagenic agent to genetically alter RNA expression profiles, and then to construct testable hypotheses as to the function of the lost regulatory site. We show fractionation mutagenesis to be a “deletion machine” in the Brassica lineage.
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26
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Affiliation(s)
- Xiaowu Wang
- The Institute of Vegetables and Flowers, Chinese Academy of Agricultural SciencesBeijing, China
| | - Michael Freeling
- Plant and Microbial Biology, University of CaliforniaBerkeley, CA, USA
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27
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Turco G, Schnable JC, Pedersen B, Freeling M. Automated conserved non-coding sequence (CNS) discovery reveals differences in gene content and promoter evolution among grasses. Front Plant Sci 2013; 4:170. [PMID: 23874343 PMCID: PMC3708275 DOI: 10.3389/fpls.2013.00170] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 05/13/2013] [Indexed: 05/07/2023]
Abstract
Conserved non-coding sequences (CNS) are islands of non-coding sequence that, like protein coding exons, show less divergence in sequence between related species than functionless DNA. Several CNSs have been demonstrated experimentally to function as cis-regulatory regions. However, the specific functions of most CNSs remain unknown. Previous searches for CNS in plants have either anchored on exons and only identified nearby sequences or required years of painstaking manual annotation. Here we present an open source tool that can accurately identify CNSs between any two related species with sequenced genomes, including both those immediately adjacent to exons and distal sequences separated by >12 kb of non-coding sequence. We have used this tool to characterize new motifs, associate CNSs with additional functions, and identify previously undetected genes encoding RNA and protein in the genomes of five grass species. We provide a list of 15,363 orthologous CNSs conserved across all grasses tested. We were also able to identify regulatory sequences present in the common ancestor of grasses that have been lost in one or more extant grass lineages. Lists of orthologous gene pairs and associated CNSs are provided for reference inbred lines of arabidopsis, Japonica rice, foxtail millet, sorghum, brachypodium, and maize.
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Affiliation(s)
| | - James C. Schnable
- *Correspondence: James C. Schnable and Michael Freeling, Department of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, CA 94720, USA e-mail: ;
| | | | - Michael Freeling
- *Correspondence: James C. Schnable and Michael Freeling, Department of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, CA 94720, USA e-mail: ;
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28
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Freeling M, Woodhouse MR, Subramaniam S, Turco G, Lisch D, Schnable JC. Fractionation mutagenesis and similar consequences of mechanisms removing dispensable or less-expressed DNA in plants. Curr Opin Plant Biol 2012; 15:131-9. [PMID: 22341793 DOI: 10.1016/j.pbi.2012.01.015] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 12/07/2011] [Accepted: 01/21/2012] [Indexed: 05/06/2023]
Abstract
Unlike in mammals, plants rapidly delete functionless, nonrepetitive DNA from their genomes. Following paleopolyploidies, duplicate genes are deleted by intrachromosomal recombination. This may explain how flowering plants have survived multiple whole genome duplications. Genes are disproportionately lost from one parental subgenome, the subgenome that is less expressed in the polyploid. The origin of this unbalanced expression between genomes remains unknown. The consequences of the tradeoffs between transposon repression and gene expression represent one potential explanation of genome dominance. If so, the same mechanisms may act in heterosis: genome dominance is like inbreeding depression. Regulatory DNA deletion following polyploidy combined with abundant RNA-seq expression datasets are being used to generate testable hypothesizes regarding the function of specific cis-regulatory sequences.
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Affiliation(s)
- Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
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29
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Abstract
The grasses, Poaceae, are one of the largest and most successful angiosperm families. Like many radiations of flowering plants, the divergence of the major grass lineages was preceded by a whole-genome duplication (WGD), although these events are not rare for flowering plants. By combining identification of syntenic gene blocks with measures of gene pair divergence and different frequencies of ancient gene loss, we have separated the two subgenomes present in modern grasses. Reciprocal loss of duplicated genes or genomic regions has been hypothesized to reproductively isolate populations and, thus, speciation. However, in contrast to previous studies in yeast and teleost fishes, we found very little evidence of reciprocal loss of homeologous genes between the grasses, suggesting that post-WGD gene loss may not be the cause of the grass radiation. The sets of homeologous and orthologous genes and predicted locations of deleted genes identified in this study, as well as links to the CoGe comparative genomics web platform for analyzing pan-grass syntenic regions, are provided along with this paper as a resource for the grass genetics community.
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Affiliation(s)
- James C Schnable
- Department of Plant and Microbial Biology, University of California-Berkeley, CA, USA
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30
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Abstract
• Whole genome duplication events provide a lineage with a large reservoir of genes that can be molded by evolutionary forces into phenotypes that fit alternative environments. A well-studied whole genome duplication, the α-event, occurred in an ancestor of the model plant Arabidopsis thaliana. Retained segments of the α-event have been defined in recent years in the form of duplicate protein coding sequences (α-pairs) and associated conserved noncoding DNA sequences (CNSs). Our aim was to identify any association between CNSs and α-pair co-functionality at the gene expression level. • Here, we tested for correlation between CNS counts and α-pair co-expression and expression intensity across nine expression datasets: aerial tissue, flowers, leaves, roots, rosettes, seedlings, seeds, shoots and whole plants. • We provide evidence for a putative regulatory role of the CNSs. The association of CNSs with α-pair co-expression and expression intensity varied by gene function, subgene position and the presence of transcription factor binding motifs. A range of possible CNS regulatory mechanisms, including intron-mediated enhancement, messenger RNA fold stability and transcriptional regulation, are discussed. • This study provides a framework to understand how CNS motifs are involved in the maintenance of gene expression after a whole genome duplication event.
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Affiliation(s)
- Jacob B Spangler
- Department of Genetics & Biochemistry, Clemson University, Clemson, SC 29634, USA
| | - Sabarinath Subramaniam
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - F Alex Feltus
- Department of Genetics & Biochemistry, Clemson University, Clemson, SC 29634, USA
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31
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Schnable JC, Wang X, Pires JC, Freeling M. Escape from preferential retention following repeated whole genome duplications in plants. Front Plant Sci 2012; 3:94. [PMID: 22639677 PMCID: PMC3355610 DOI: 10.3389/fpls.2012.00094] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 04/24/2012] [Indexed: 05/21/2023]
Abstract
The well supported gene dosage hypothesis predicts that genes encoding proteins engaged in dose-sensitive interactions cannot be reduced back to single copies once all interacting partners are simultaneously duplicated in a whole genome duplication. The genomes of extant flowering plants are the result of many sequential rounds of whole genome duplication, yet the fraction of genomes devoted to encoding complex molecular machines does not increase as fast as expected through multiple rounds of whole genome duplications. Using parallel interspecies genomic comparisons in the grasses and crucifers, we demonstrate that genes retained as duplicates following a whole genome duplication have only a 50% chance of being retained as duplicates in a second whole genome duplication. Genes which fractionated to a single copy following a second whole genome duplication tend to be the member of a gene pair with less complex promoters, lower levels of expression, and to be under lower levels of purifying selection. We suggest the copy with lower levels of expression and less purifying selection contributes less to effective gene-product dosage and therefore is under less dosage constraint in future whole genome duplications, providing an explanation for why flowering plant genomes are not overrun with subunits of large dose-sensitive protein complexes.
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Affiliation(s)
- James C. Schnable
- Freeling Lab, Plant and Microbial Biology, University of California – BerkeleyBerkeley, CA, USA
| | - Xiaowu Wang
- Molecular Genetics Lab, Biotechnology Department, Institute of vegetables and flowers, Chinese Academy of Agricultural SciencesBeijing, China
| | - J. Chris Pires
- Biological Sciences, Bond Life Sciences Center, University of MissouriColombia, MO, USA
| | - Michael Freeling
- Freeling Lab, Plant and Microbial Biology, University of California – BerkeleyBerkeley, CA, USA
- *Correspondence: Michael Freeling, Freeling Lab, Plant and Microbial Biology, University of California – Berkeley, 111 Koshland Hall, PMB, Berkeley, CA 94720, USA. e-mail:
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Woodhouse MR, Tang H, Freeling M. Different gene families in Arabidopsis thaliana transposed in different epochs and at different frequencies throughout the rosids. Plant Cell 2011; 23:4241-53. [PMID: 22180627 PMCID: PMC3269863 DOI: 10.1105/tpc.111.093567] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Certain types of gene families, such as those encoding most families of transcription factors, maintain their chromosomal syntenic positions throughout angiosperm evolutionary time. Other nonsyntenic gene families are prone to deletion, tandem duplication, and transposition. Here, we describe the chromosomal positional history of all genes in Arabidopsis thaliana throughout the rosid superorder. We introduce a public database where researchers can look up the positional history of their favorite A. thaliana gene or gene family. Finally, we show that specific gene families transposed at specific points in evolutionary time, particularly after whole-genome duplication events in the Brassicales, and suggest that genes in mobile gene families are under different selection pressure than syntenic genes.
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Affiliation(s)
- Margaret R Woodhouse
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
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Abstract
Gene expression is controlled by the complex interaction of transcription factors binding to promoters and other regulatory DNA elements. One common characteristic of the genomic regions associated with regulatory proteins is a pronounced sensitivity to DNase I digestion. We generated genome-wide high-resolution maps of DNase I hypersensitive (DH) sites from both seedling and callus tissues of rice (Oryza sativa). Approximately 25% of the DH sites from both tissues were found in putative promoters, indicating that the vast majority of the gene regulatory elements in rice are not located in promoter regions. We found 58% more DH sites in the callus than in the seedling. For DH sites detected in both the seedling and callus, 31% displayed significantly different levels of DNase I sensitivity within the two tissues. Genes that are differentially expressed in the seedling and callus were frequently associated with DH sites in both tissues. The DNA sequences contained within the DH sites were hypomethylated, consistent with what is known about active gene regulatory elements. Interestingly, tissue-specific DH sites located in the promoters showed a higher level of DNA methylation than the average DNA methylation level of all the DH sites located in the promoters. A distinct elevation of H3K27me3 was associated with intergenic DH sites. These results suggest that epigenetic modifications play a role in the dynamic changes of the numbers and DNase I sensitivity of DH sites during development.
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Affiliation(s)
- Wenli Zhang
- Department of Horticulture, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Eichten SR, Swanson-Wagner RA, Schnable JC, Waters AJ, Hermanson PJ, Liu S, Yeh CT, Jia Y, Gendler K, Freeling M, Schnable PS, Vaughn MW, Springer NM. Heritable epigenetic variation among maize inbreds. PLoS Genet 2011; 7:e1002372. [PMID: 22125494 PMCID: PMC3219600 DOI: 10.1371/journal.pgen.1002372] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 09/20/2011] [Indexed: 11/26/2022] Open
Abstract
Epigenetic variation describes heritable differences that are not attributable to changes in DNA sequence. There is the potential for pure epigenetic variation that occurs in the absence of any genetic change or for more complex situations that involve both genetic and epigenetic differences. Methylation of cytosine residues provides one mechanism for the inheritance of epigenetic information. A genome-wide profiling of DNA methylation in two different genotypes of Zea mays (ssp. mays), an organism with a complex genome of interspersed genes and repetitive elements, allowed the identification and characterization of examples of natural epigenetic variation. The distribution of DNA methylation was profiled using immunoprecipitation of methylated DNA followed by hybridization to a high-density tiling microarray. The comparison of the DNA methylation levels in the two genotypes, B73 and Mo17, allowed for the identification of approximately 700 differentially methylated regions (DMRs). Several of these DMRs occur in genomic regions that are apparently identical by descent in B73 and Mo17 suggesting that they may be examples of pure epigenetic variation. The methylation levels of the DMRs were further studied in a panel of near-isogenic lines to evaluate the stable inheritance of the methylation levels and to assess the contribution of cis- and trans- acting information to natural epigenetic variation. The majority of DMRs that occur in genomic regions without genetic variation are controlled by cis-acting differences and exhibit relatively stable inheritance. This study provides evidence for naturally occurring epigenetic variation in maize, including examples of pure epigenetic variation that is not conditioned by genetic differences. The epigenetic differences are variable within maize populations and exhibit relatively stable trans-generational inheritance. The detected examples of epigenetic variation, including some without tightly linked genetic variation, may contribute to complex trait variation. Heritable variation within a species provides the basis for natural and artificial selection. A substantial portion of heritable variation is based on alterations in DNA sequence among individuals and is termed genetic variation. There is also evidence for epigenetic variation, which refers to heritable differences that are not caused by DNA sequence changes. Methylation of cytosine residues provides one molecular mechanism for epigenetic variation in many eukaryotic species. The genome-wide distribution of DNA methylation was assessed in two different inbred genotypes of maize to identify differentially methylated regions that may contribute to epigenetic variation. There are hundreds of genomic regions that have differences in DNA methylation levels in these two different genotypes, including methylation differences in regions without genetic variation. By studying the inheritance of the differential methylation in near-isogenic progeny of the two inbred lines, it is possible to demonstrate relatively stable inheritance of epigenetic variation, even in the absence of DNA sequence changes. The epigenetic variation among individuals of the same species may provide important contributions to phenotypic variation within a species even in the absence of genetic differences.
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Affiliation(s)
- Steve R. Eichten
- Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Ruth A. Swanson-Wagner
- Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - James C. Schnable
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Amanda J. Waters
- Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Peter J. Hermanson
- Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Sanzhen Liu
- Iowa State University, Ames, Iowa, United States of America
| | - Cheng-Ting Yeh
- Iowa State University, Ames, Iowa, United States of America
| | - Yi Jia
- Iowa State University, Ames, Iowa, United States of America
| | - Karla Gendler
- Texas Advanced Computing Center, University of Texas–Austin, Austin, Texas, United States of America
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | | | - Matthew W. Vaughn
- Texas Advanced Computing Center, University of Texas–Austin, Austin, Texas, United States of America
- * E-mail: (MWV); (NMS)
| | - Nathan M. Springer
- Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, Saint Paul, Minnesota, United States of America
- * E-mail: (MWV); (NMS)
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Wang X, Wang H, Wang J, Sun R, Wu J, Liu S, Bai Y, Mun JH, Bancroft I, Cheng F, Huang S, Li X, Hua W, Wang J, Wang X, Freeling M, Pires JC, Paterson AH, Chalhoub B, Wang B, Hayward A, Sharpe AG, Park BS, Weisshaar B, Liu B, Li B, Liu B, Tong C, Song C, Duran C, Peng C, Geng C, Koh C, Lin C, Edwards D, Mu D, Shen D, Soumpourou E, Li F, Fraser F, Conant G, Lassalle G, King GJ, Bonnema G, Tang H, Wang H, Belcram H, Zhou H, Hirakawa H, Abe H, Guo H, Wang H, Jin H, Parkin IAP, Batley J, Kim JS, Just J, Li J, Xu J, Deng J, Kim JA, Li J, Yu J, Meng J, Wang J, Min J, Poulain J, Wang J, Hatakeyama K, Wu K, Wang L, Fang L, Trick M, Links MG, Zhao M, Jin M, Ramchiary N, Drou N, Berkman PJ, Cai Q, Huang Q, Li R, Tabata S, Cheng S, Zhang S, Zhang S, Huang S, Sato S, Sun S, Kwon SJ, Choi SR, Lee TH, Fan W, Zhao X, Tan X, Xu X, Wang Y, Qiu Y, Yin Y, Li Y, Du Y, Liao Y, Lim Y, Narusaka Y, Wang Y, Wang Z, Li Z, Wang Z, Xiong Z, Zhang Z. The genome of the mesopolyploid crop species Brassica rapa. Nat Genet 2011; 43:1035-9. [PMID: 21873998 DOI: 10.1038/ng.919] [Citation(s) in RCA: 1258] [Impact Index Per Article: 96.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 08/03/2011] [Indexed: 11/09/2022]
Abstract
We report the annotation and analysis of the draft genome sequence of Brassica rapa accession Chiifu-401-42, a Chinese cabbage. We modeled 41,174 protein coding genes in the B. rapa genome, which has undergone genome triplication. We used Arabidopsis thaliana as an outgroup for investigating the consequences of genome triplication, such as structural and functional evolution. The extent of gene loss (fractionation) among triplicated genome segments varies, with one of the three copies consistently retaining a disproportionately large fraction of the genes expected to have been present in its ancestor. Variation in the number of members of gene families present in the genome may contribute to the remarkable morphological plasticity of Brassica species. The B. rapa genome sequence provides an important resource for studying the evolution of polyploid genomes and underpins the genetic improvement of Brassica oil and vegetable crops.
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Affiliation(s)
- Xiaowu Wang
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences (IVF, CAAS), Beijing, China
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Tang H, Lyons E, Pedersen B, Schnable JC, Paterson AH, Freeling M. Screening synteny blocks in pairwise genome comparisons through integer programming. BMC Bioinformatics 2011; 12:102. [PMID: 21501495 PMCID: PMC3088904 DOI: 10.1186/1471-2105-12-102] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Accepted: 04/18/2011] [Indexed: 12/01/2022] Open
Abstract
Background It is difficult to accurately interpret chromosomal correspondences such as true orthology and paralogy due to significant divergence of genomes from a common ancestor. Analyses are particularly problematic among lineages that have repeatedly experienced whole genome duplication (WGD) events. To compare multiple "subgenomes" derived from genome duplications, we need to relax the traditional requirements of "one-to-one" syntenic matchings of genomic regions in order to reflect "one-to-many" or more generally "many-to-many" matchings. However this relaxation may result in the identification of synteny blocks that are derived from ancient shared WGDs that are not of interest. For many downstream analyses, we need to eliminate weak, low scoring alignments from pairwise genome comparisons. Our goal is to objectively select subset of synteny blocks whose total scores are maximized while respecting the duplication history of the genomes in comparison. We call this "quota-based" screening of synteny blocks in order to appropriately fill a quota of syntenic relationships within one genome or between two genomes having WGD events. Results We have formulated the synteny block screening as an optimization problem known as "Binary Integer Programming" (BIP), which is solved using existing linear programming solvers. The computer program QUOTA-ALIGN performs this task by creating a clear objective function that maximizes the compatible set of synteny blocks under given constraints on overlaps and depths (corresponding to the duplication history in respective genomes). Such a procedure is useful for any pairwise synteny alignments, but is most useful in lineages affected by multiple WGDs, like plants or fish lineages. For example, there should be a 1:2 ploidy relationship between genome A and B if genome B had an independent WGD subsequent to the divergence of the two genomes. We show through simulations and real examples using plant genomes in the rosid superorder that the quota-based screening can eliminate ambiguous synteny blocks and focus on specific genomic evolutionary events, like the divergence of lineages (in cross-species comparisons) and the most recent WGD (in self comparisons). Conclusions The QUOTA-ALIGN algorithm screens a set of synteny blocks to retain only those compatible with a user specified ploidy relationship between two genomes. These blocks, in turn, may be used for additional downstream analyses such as identifying true orthologous regions in interspecific comparisons. There are two major contributions of QUOTA-ALIGN: 1) reducing the block screening task to a BIP problem, which is novel; 2) providing an efficient software pipeline starting from all-against-all BLAST to the screened synteny blocks with dot plot visualizations. Python codes and full documentations are publicly available http://github.com/tanghaibao/quota-alignment. QUOTA-ALIGN program is also integrated as a major component in SynMap http://genomevolution.com/CoGe/SynMap.pl, offering easier access to thousands of genomes for non-programmers.
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Affiliation(s)
- Haibao Tang
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
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Schnable JC, Freeling M. Genes identified by visible mutant phenotypes show increased bias toward one of two subgenomes of maize. PLoS One 2011; 6:e17855. [PMID: 21423772 PMCID: PMC3053395 DOI: 10.1371/journal.pone.0017855] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 02/10/2011] [Indexed: 12/31/2022] Open
Abstract
Not all genes are created equal. Despite being supported by sequence conservation and expression data, knockout homozygotes of many genes show no visible effects, at least under laboratory conditions. We have identified a set of maize (Zea mays L.) genes which have been the subject of a disproportionate share of publications recorded at MaizeGDB. We manually anchored these "classical" maize genes to gene models in the B73 reference genome, and identified syntenic orthologs in other grass genomes. In addition to proofing the most recent version 2 maize gene models, we show that a subset of these genes, those that were identified by morphological phenotype prior to cloning, are retained at syntenic locations throughout the grasses at much higher levels than the average expressed maize gene, and are preferentially found on the maize1 subgenome even with a duplicate copy is still retained on the opposite subgenome. Maize1 is the subgenome that experienced less gene loss following the whole genome duplication in maize lineage 5-12 million years ago and genes located on this subgenome tend to be expressed at higher levels in modern maize. Links to the web based software that supported our syntenic analyses in the grasses should empower further research and support teaching involving the history of maize genetic research. Our findings exemplify the concept of "grasses as a single genetic system," where what is learned in one grass may be applied to another.
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Affiliation(s)
- James C Schnable
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America.
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Abstract
We here develop computational methods to facilitate use of 454 whole genome shotgun sequencing to identify mutations in Escherichia coli K12. We had Roche sequence eight related strains derived as spontaneous mutants in a background without a whole genome sequence. They provided difference tables based on assembling each genome to reference strain E. coli MG1655 (NC_000913). Due to the evolutionary distance to MG1655, these contained a large number of both false negatives and positives. By manual analysis of the dataset, we detected all the known mutations (24 at nine locations) and identified and genetically confirmed new mutations necessary and sufficient for the phenotypes we had selected in four strains. We then had Roche assemble contigs de novo, which we further assembled to full-length pseudomolecules based on synteny with MG1655. This hybrid method facilitated detection of insertion mutations and allowed annotation from MG1655. After removing one genome with less than the optimal 20- to 30-fold sequence coverage, we identified 544 putative polymorphisms that included all of the known and selected mutations apart from insertions. Finally, we detected seven new mutations in a total of only 41 candidates by comparing single genomes to composite data for the remaining six and using a ranking system to penalize homopolymer sequencing and misassembly errors. An additional benefit of the analysis is a table of differences between MG1655 and a physiologically robust E. coli wild-type strain NCM3722. Both projects were greatly facilitated by use of comparative genomics tools in the CoGe software package (http://genomevolution.org/).
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Affiliation(s)
- Eric Lyons
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
- * E-mail:
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
| | - Sydney Kustu
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
| | - William Inwood
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
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Schnable JC, Pedersen BS, Subramaniam S, Freeling M. Dose-sensitivity, conserved non-coding sequences, and duplicate gene retention through multiple tetraploidies in the grasses. Front Plant Sci 2011; 2:2. [PMID: 22645525 PMCID: PMC3355796 DOI: 10.3389/fpls.2011.00002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Accepted: 02/19/2011] [Indexed: 05/08/2023]
Abstract
Whole genome duplications, or tetraploidies, are an important source of increased gene content. Following whole genome duplication, duplicate copies of many genes are lost from the genome. This loss of genes is biased both in the classes of genes deleted and the subgenome from which they are lost. Many or all classes are genes preferentially retained as duplicate copies are engaged in dose sensitive protein-protein interactions, such that deletion of any one duplicate upsets the status quo of subunit concentrations, and presumably lowers fitness as a result. Transcription factors are also preferentially retained following every whole genome duplications studied. This has been explained as a consequence of protein-protein interactions, just as for other highly retained classes of genes. We show that the quantity of conserved noncoding sequences (CNSs) associated with genes predicts the likelihood of their retention as duplicate pairs following whole genome duplication. As many CNSs likely represent binding sites for transcriptional regulators, we propose that the likelihood of gene retention following tetraploidy may also be influenced by dose-sensitive protein-DNA interactions between the regulatory regions of CNS-rich genes - nicknamed bigfoot genes - and the proteins that bind to them. Using grass genomes, we show that differential loss of CNSs from one member of a pair following the pre-grass tetraploidy reduces its chance of retention in the subsequent maize lineage tetraploidy.
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Affiliation(s)
- James C. Schnable
- Department of Plant and Microbial Biology, University of California BerkeleyBerkeley, CA, USA
| | - Brent S. Pedersen
- Department of Plant and Microbial Biology, University of California BerkeleyBerkeley, CA, USA
| | - Sabarinath Subramaniam
- Department of Plant and Microbial Biology, University of California BerkeleyBerkeley, CA, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California BerkeleyBerkeley, CA, USA
- *Correspondence: Michael Freeling, Department of Plant and Microbial Biology, University of California-Berkeley, 111 Koshland Hall, Berkeley, CA 94720, United States of America e-mail:
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Woodward JB, Abeydeera ND, Paul D, Phillips K, Rapala-Kozik M, Freeling M, Begley TP, Ealick SE, McSteen P, Scanlon MJ. A maize thiamine auxotroph is defective in shoot meristem maintenance. Plant Cell 2010; 22:3305-17. [PMID: 20971897 PMCID: PMC2990124 DOI: 10.1105/tpc.110.077776] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 08/27/2010] [Accepted: 09/25/2010] [Indexed: 05/18/2023]
Abstract
Plant shoots undergo organogenesis throughout their life cycle via the perpetuation of stem cell pools called shoot apical meristems (SAMs). SAM maintenance requires the coordinated equilibrium between stem cell division and differentiation and is regulated by integrated networks of gene expression, hormonal signaling, and metabolite sensing. Here, we show that the maize (Zea mays) mutant bladekiller1-R (blk1-R) is defective in leaf blade development and meristem maintenance and exhibits a progressive reduction in SAM size that results in premature shoot abortion. Molecular markers for stem cell maintenance and organ initiation reveal that both of these meristematic functions are progressively compromised in blk1-R mutants, especially in the inflorescence and floral meristems. Positional cloning of blk1-R identified a predicted missense mutation in a highly conserved amino acid encoded by thiamine biosynthesis2 (thi2). Consistent with chromosome dosage studies suggesting that blk1-R is a null mutation, biochemical analyses confirm that the wild-type THI2 enzyme copurifies with a thiazole precursor to thiamine, whereas the mutant enzyme does not. Heterologous expression studies confirm that THI2 is targeted to chloroplasts. All blk1-R mutant phenotypes are rescued by exogenous thiamine supplementation, suggesting that blk1-R is a thiamine auxotroph. These results provide insight into the role of metabolic cofactors, such as thiamine, during the proliferation of stem and initial cell populations.
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Affiliation(s)
- John B. Woodward
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | | | - Debamita Paul
- Department of Chemistry, Cornell University, Ithaca, New York 14853
| | - Kimberly Phillips
- Biology Department, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Maria Rapala-Kozik
- Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Krakow 30-387, Poland
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94704
| | - Tadhg P. Begley
- Department of Chemistry, Texas A&M University, College Station, Texas 77842
| | - Steven E. Ealick
- Department of Chemistry, Cornell University, Ithaca, New York 14853
| | - Paula McSteen
- Biology Department, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Michael J. Scanlon
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
- Address correspondence to
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Woodhouse MR, Schnable JC, Pedersen BS, Lyons E, Lisch D, Subramaniam S, Freeling M. Following tetraploidy in maize, a short deletion mechanism removed genes preferentially from one of the two homologs. PLoS Biol 2010; 8:e1000409. [PMID: 20613864 PMCID: PMC2893956 DOI: 10.1371/journal.pbio.1000409] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 05/20/2010] [Indexed: 12/02/2022] Open
Abstract
Following genome duplication and selfish DNA expansion, maize used a heretofore unknown mechanism to shed redundant genes and functionless DNA with bias toward one of the parental genomes. Previous work in Arabidopsis showed that after an ancient tetraploidy event, genes were preferentially removed from one of the two homeologs, a process known as fractionation. The mechanism of fractionation is unknown. We sought to determine whether such preferential, or biased, fractionation exists in maize and, if so, whether a specific mechanism could be implicated in this process. We studied the process of fractionation using two recently sequenced grass species: sorghum and maize. The maize lineage has experienced a tetraploidy since its divergence from sorghum approximately 12 million years ago, and fragments of many knocked-out genes retain enough sequence similarity to be easily identifiable. Using sorghum exons as the query sequence, we studied the fate of both orthologous genes in maize following the maize tetraploidy. We show that genes are predominantly lost, not relocated, and that single-gene loss by deletion is the rule. Based on comparisons with orthologous sorghum and rice genes, we also infer that the sequences present before the deletion events were flanked by short direct repeats, a signature of intra-chromosomal recombination. Evidence of this deletion mechanism is found 2.3 times more frequently on one of the maize homeologs, consistent with earlier observations of biased fractionation. The over-fractionated homeolog is also a greater than 3-fold better target for transposon removal, but does not have an observably higher synonymous base substitution rate, nor could we find differentially placed methylation domains. We conclude that fractionation is indeed biased in maize and that intra-chromosomal or possibly a similar illegitimate recombination is the primary mechanism by which fractionation occurs. The mechanism of intra-chromosomal recombination explains the observed bias in both gene and transposon loss in the maize lineage. The existence of fractionation bias demonstrates that the frequency of deletion is modulated. Among the evolutionary benefits of this deletion/fractionation mechanism is bulk DNA removal and the generation of novel combinations of regulatory sequences and coding regions. All genomes can accumulate dispensable DNA in the form of duplications of individual genes or even partial or whole genome duplications. Genomes also can accumulate selfish DNA elements. Duplication events specifically are often followed by extensive gene loss. The maize genome is particularly extreme, having become tetraploid 10 million years ago and played host to massive transposon amplifications. We compared the genome of sorghum (which is homologous to the pre-tetraploid maize genome) with the two identifiable parental genomes retained in maize. The two maize genomes differ greatly: one of the parental genomes has lost 2.3 times more genes than the other, and the selfish DNA regions between genes were even more frequently lost, suggesting maize can distinguish between the parental genomes present in the original tetraploid. We show that genes are actually lost, not simply relocated. Deletions were rarely longer than a single gene, and occurred between repeated DNA sequences, suggesting mis-recombination as a mechanism of gene removal. We hypothesize an epigenetic mechanism of genome distinction to account for the selective loss. To the extent that the rate of base substitutions tracks time, we neither support nor refute claims of maize allotetraploidy. Finally, we explain why it makes sense that purifying selection in mammals does not operate at all like the gene and genome deletion program we describe here.
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Affiliation(s)
- Margaret R. Woodhouse
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - James C. Schnable
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Brent S. Pedersen
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Eric Lyons
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Damon Lisch
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Shabarinath Subramaniam
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
- * E-mail:
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Abstract
The ability to stain mature pollen grains for the presence of alcohol dehydrogenase (ADH) activity permits the quantitation of ADH( +) gametophytes at frequencies below 10(-6). This resolution allows reversion and genetic fine structure analyses. The rationale of pollen analysis follows Nelson's prototype studies with waxy. As with the waxy gene, revertant frequencies for seven Adh1-deficient ( Adh1(-)) alleles appear to be in excess of microbially derived expectations. Each of the seven Adh1(-) alleles were derived from one of three naturally occurring isoalleles. Based on Schwartz's protein level characterizations of the mutants' products, it was anticipated that the seven Adh1(-) alleles should recombine to yield ADH(+) cistrons in certain pairwise combinations. This expectation was not met. The parental "wild-type" isoalleles from which the mutants were derived appear to be structurally divergent. The discussion interprets these data in view of understanding naturally occurring cistronic variation.
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Affiliation(s)
- M Freeling
- Department of Genetics, University of California, Berkeley, California 94720
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44
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Abstract
Allozyme balances serve as markers of quantitative behavior of electrophoretically distinguishable alleles. By the use of ADH Set I allozyme balances, it is demonstrated that all Adh1-S/Adh1-F individuals from more than 20 diverse S/F families exhibit a reciprocal correlation between Adh1 quantitative behavior in two maize organs: the scutellum and primary root. Within an electrophoretic mobility class, the Adh1 allele that is relatively underexpressed in the scutellum is relatively overexpressed in the primary root, and vice versa. Segregation tests prove that this "reciprocal effect" is the property of a cis-acting site that is closely linked to or within the Adh1 structural gene, and it is not affected by diverse genetic backgrounds. Immunological and [(3)H]-leucine incorporation experiments establish that Adh1 quantitative variants differ in ADH1.ADH1 synthetic rates in the anaerobic primary root. The reciprocal-effect phenomenon suggests that the cis-acting loci controlling Adh1 quantitative expression in each respective organ are at least in close proximity, or may share common DNA sequences. We discuss the possibility that the reciprocal-effect locus is a regulatory component of the Adh1 cistron.
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Affiliation(s)
- J C Woodman
- Department of Genetics, University of California, Berkeley, California 94720
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45
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Abstract
Local gene duplication is a prominent mechanism of gene copy number expansion. Elucidating the mechanisms by which local duplicates arise is necessary in understanding the evolution of genomes and their host organisms. Chromosome one of Arabidopsis thaliana contains an 81-gene array subdivided into 27 triplet units (t-units), with each t-unit containing three pre-transfer RNA genes. We utilized phylogenetic tree reconstructions and comparative genomics to order the events leading to the array's formation, and propose a model using unequal crossing-over as the primary mechanism of array formation. The model is supported by additional phylogenetic information from intergenic spacer sequences separating each t-unit, comparative analysis to an orthologous array of 12 t-units in the sister taxa Arabidopsis lyrata, and additional modeling using a stochastic simulation of orthologous array divergence. Lastly, comparative phylogenetic analysis demonstrates that the two orthologous t-unit arrays undergo concerted evolution within each taxa and are likely fluctuating in copy number under neutral evolutionary drift. These findings hold larger implications for future research concerning gene and genome evolution.
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Affiliation(s)
- Joshua Kane
- Department of Plant and Microbial Biology, University of California at Berkeley, 311 Koshland Hall, Berkeley, CA 94720, USA
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46
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Abstract
The next decade will see essentially completed sequences for multiple branches of virtually all angiosperm clades that include major crops and/or botanical models. These sequences will provide a powerful framework for relating genome-level events to aspects of morphological and physiological variation that have contributed to the colonization of much of the planet by angiosperms. Clarification of the fundamental angiosperm gene set, its arrangement, lineage-specific variations in gene repertoire and arrangement, and the fates of duplicated gene pairs will advance knowledge of functional and regulatory diversity and perhaps shed light on adaptation by lineages to whole-genome duplication, which is a distinguishing feature of angiosperm evolution. Better understanding of the relationships among angiosperm genomes promises to provide a firm foundation upon which to base translational genomics: the leveraging of hard-won structural and functional genomic information from crown botanical models to dissect novel and, in some cases, economically important features in many additional organisms.
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Affiliation(s)
- Andrew H Paterson
- Department of Plant Biology, University of Georgia, Athens, Georgia.
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Freeling M, Subramaniam S. Conserved noncoding sequences (CNSs) in higher plants. Curr Opin Plant Biol 2009; 12:126-32. [PMID: 19249238 DOI: 10.1016/j.pbi.2009.01.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Revised: 01/22/2009] [Accepted: 01/22/2009] [Indexed: 05/09/2023]
Abstract
Plant conserved noncoding sequences (CNSs)--a specific category of phylogenetic footprint--have been shown experimentally to function. No plant CNS is conserved to the extent that ultraconserved noncoding sequences are conserved in vertebrates. Plant CNSs are enriched in known transcription factor or other cis-acting binding sites, and are usually clustered around genes. Genes that encode transcription factors and/or those that respond to stimuli are particularly CNS-rich. Only rarely could this function involve small RNA binding. Some transcribed CNSs encode short translation products as a form of negative control. Approximately 4% of Arabidopsis gene content is estimated to be both CNS-rich and occupies a relatively long stretch of chromosome: Bigfoot genes (long phylogenetic footprints). We discuss a 'DNA-templated protein assembly' idea that might help explain Bigfoot gene CNSs.
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Affiliation(s)
- Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
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Paterson AH, Bowers JE, Bruggmann R, Dubchak I, Grimwood J, Gundlach H, Haberer G, Hellsten U, Mitros T, Poliakov A, Schmutz J, Spannagl M, Tang H, Wang X, Wicker T, Bharti AK, Chapman J, Feltus FA, Gowik U, Grigoriev IV, Lyons E, Maher CA, Martis M, Narechania A, Otillar RP, Penning BW, Salamov AA, Wang Y, Zhang L, Carpita NC, Freeling M, Gingle AR, Hash CT, Keller B, Klein P, Kresovich S, McCann MC, Ming R, Peterson DG, Mehboob-ur-Rahman, Ware D, Westhoff P, Mayer KFX, Messing J, Rokhsar DS. The Sorghum bicolor genome and the diversification of grasses. Nature 2009; 457:551-6. [PMID: 19189423 DOI: 10.1038/nature07723] [Citation(s) in RCA: 1628] [Impact Index Per Article: 108.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Sorghum, an African grass related to sugar cane and maize, is grown for food, feed, fibre and fuel. We present an initial analysis of the approximately 730-megabase Sorghum bicolor (L.) Moench genome, placing approximately 98% of genes in their chromosomal context using whole-genome shotgun sequence validated by genetic, physical and syntenic information. Genetic recombination is largely confined to about one-third of the sorghum genome with gene order and density similar to those of rice. Retrotransposon accumulation in recombinationally recalcitrant heterochromatin explains the approximately 75% larger genome size of sorghum compared with rice. Although gene and repetitive DNA distributions have been preserved since palaeopolyploidization approximately 70 million years ago, most duplicated gene sets lost one member before the sorghum-rice divergence. Concerted evolution makes one duplicated chromosomal segment appear to be only a few million years old. About 24% of genes are grass-specific and 7% are sorghum-specific. Recent gene and microRNA duplications may contribute to sorghum's drought tolerance.
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Affiliation(s)
- Andrew H Paterson
- Plant Genome Mapping Laboratory, University of Georgia, Athens, Georgia 30602, USA.
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49
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Abstract
Each mode of gene duplication (tandem, tetraploid, segmental, transpositional) retains genes in a biased manner. A reciprocal relationship exists between plant genes retained postpaleotetraploidy versus genes retained after an ancient tandem duplication. Among the models (C, neofunctionalization, balanced gene drive) and ideas that might explain this relationship, only balanced gene drive predicts reciprocity. The gene balance hypothesis explains that more "connected" genes--by protein-protein interactions in a heteromer, for example--are less likely to be retained as a tandem or transposed duplicate and are more likely to be retained postpaleotetraploidy; otherwise, selectively negative dosage effects are created. Biased duplicate retention is an instant and neutral by-product, a spandrel, of purifying selection. Balanced gene drive expanded plant gene families, including those encoding proteasomal proteins, protein kinases, motors, and transcription factors, with each paleotetraploidy, which could explain trends involving complexity. Balanced gene drive is a saltation mechanism in the mutationist tradition.
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Affiliation(s)
- Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
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Lyons E, Pedersen B, Kane J, Alam M, Ming R, Tang H, Wang X, Bowers J, Paterson A, Lisch D, Freeling M. Finding and comparing syntenic regions among Arabidopsis and the outgroups papaya, poplar, and grape: CoGe with rosids. Plant Physiol 2008; 148:1772-81. [PMID: 18952863 PMCID: PMC2593677 DOI: 10.1104/pp.108.124867] [Citation(s) in RCA: 273] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Accepted: 10/19/2008] [Indexed: 05/18/2023]
Abstract
In addition to the genomes of Arabidopsis (Arabidopsis thaliana) and poplar (Populus trichocarpa), two near-complete rosid genome sequences, grape (Vitis vinifera) and papaya (Carica papaya), have been recently released. The phylogenetic relationship among these four genomes and the placement of their three independent, fractionated tetraploidies sum to a powerful comparative genomic system. CoGe, a platform of multiple whole or near-complete genome sequences, provides an integrative Web-based system to find and align syntenic chromosomal regions and visualize the output in an intuitive and interactive manner. CoGe has been customized to specifically support comparisons among the rosids. Crucial facts and definitions are presented to clearly describe the sorts of biological questions that might be answered in part using CoGe, including patterns of DNA conservation, accuracy of annotation, transposability of individual genes, subfunctionalization and/or fractionation of syntenic gene sets, and conserved noncoding sequence content. This précis of an online tutorial, CoGe with Rosids (http://tinyurl.com/4a23pk), presents sample results graphically.
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Affiliation(s)
- Eric Lyons
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
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