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de Tomás C, Vicient CM. The Genomic Shock Hypothesis: Genetic and Epigenetic Alterations of Transposable Elements after Interspecific Hybridization in Plants. EPIGENOMES 2023; 8:2. [PMID: 38247729 PMCID: PMC10801548 DOI: 10.3390/epigenomes8010002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 12/21/2023] [Accepted: 12/24/2023] [Indexed: 01/23/2024] Open
Abstract
Transposable elements (TEs) are major components of plant genomes with the ability to change their position in the genome or to create new copies of themselves in other positions in the genome. These can cause gene disruption and large-scale genomic alterations, including inversions, deletions, and duplications. Host organisms have evolved a set of mechanisms to suppress TE activity and counter the threat that they pose to genome integrity. These includes the epigenetic silencing of TEs mediated by a process of RNA-directed DNA methylation (RdDM). In most cases, the silencing machinery is very efficient for the vast majority of TEs. However, there are specific circumstances in which TEs can evade such silencing mechanisms, for example, a variety of biotic and abiotic stresses or in vitro culture. Hybridization is also proposed as an inductor of TE proliferation. In fact, the discoverer of the transposons, Barbara McClintock, first hypothesized that interspecific hybridization provides a "genomic shock" that inhibits the TE control mechanisms leading to the mobilization of TEs. However, the studies carried out on this topic have yielded diverse results, showing in some cases a total absence of mobilization or being limited to only some TE families. Here, we review the current knowledge about the impact of interspecific hybridization on TEs in plants and the possible implications of changes in the epigenetic mechanisms.
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Affiliation(s)
| | - Carlos M. Vicient
- Centre for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, 08193 Barcelona, Spain
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2
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Liu B, Zhao M. How transposable elements are recognized and epigenetically silenced in plants? CURRENT OPINION IN PLANT BIOLOGY 2023; 75:102428. [PMID: 37481986 DOI: 10.1016/j.pbi.2023.102428] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 06/27/2023] [Accepted: 06/28/2023] [Indexed: 07/25/2023]
Abstract
Plant genomes are littered with transposable elements (TEs). Because TEs are potentially highly mutagenic, host organisms have evolved a set of defense mechanisms to recognize and epigenetically silence them. Although the maintenance of TE silencing is well studied, our understanding of the initiation of TE silencing is limited, but it clearly involves small RNAs and DNA methylation. Once TEs are silent, the silent state can be maintained to subsequent generations. However, under some circumstances, such inheritance is unstable, leading to the escape of TEs to the silencing machinery, resulting in the transcriptional activation of TEs. Epigenetic control of TEs has been found to be closely linked to many other epigenetic phenomena, such as genomic imprinting, and is known to contribute to regulation of genes, especially those near TEs. Here we review and discuss the current models of TE silencing, its unstable inheritance after hybridization, and the effects of epigenetic regulation of TEs on genomic imprinting.
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Affiliation(s)
- Beibei Liu
- Department of Biology, Miami University, Oxford, OH 45056, USA
| | - Meixia Zhao
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA.
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3
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Zhang P, Mbodj A, Soundiramourtty A, Llauro C, Ghesquière A, Ingouff M, Keith Slotkin R, Pontvianne F, Catoni M, Mirouze M. Extrachromosomal circular DNA and structural variants highlight genome instability in Arabidopsis epigenetic mutants. Nat Commun 2023; 14:5236. [PMID: 37640706 PMCID: PMC10462705 DOI: 10.1038/s41467-023-41023-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 08/21/2023] [Indexed: 08/31/2023] Open
Abstract
Abundant extrachromosomal circular DNA (eccDNA) is associated with transposable element (TE) activity. However, how the eccDNA compartment is controlled by epigenetic regulations and what is its impact on the genome is understudied. Here, using long reads, we sequence both the eccDNA compartment and the genome of Arabidopsis thaliana mutant plants affected in DNA methylation and post-transcriptional gene silencing. We detect a high load of TE-derived eccDNA with truncated and chimeric forms. On the genomic side, on top of truncated and full length TE neo-insertions, we detect complex structural variations (SVs) notably at a disease resistance cluster being a natural hotspot of SV. Finally, we serendipitously identify large tandem duplications in hypomethylated plants, suggesting that SVs could have been overlooked in epigenetic mutants. We propose that a high eccDNA load may alter DNA repair pathways leading to genome instability and the accumulation of SVs, at least in plants.
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Affiliation(s)
- Panpan Zhang
- Institut de Recherche pour le Développement (IRD), Laboratory of Plant Genome and Development, Perpignan, France
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France
- University of Montpellier, Montpellier, France
| | - Assane Mbodj
- Institut de Recherche pour le Développement (IRD), Laboratory of Plant Genome and Development, Perpignan, France
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France
| | - Abirami Soundiramourtty
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France
- University of Perpignan, Perpignan, France
| | - Christel Llauro
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France
- Centre National de la Recherche Scientifique (CNRS), Laboratory of Plant Genome and Development, Perpignan, France
| | - Alain Ghesquière
- DIADE, University of Montpellier, IRD, CIRAD, Montpellier, France
| | - Mathieu Ingouff
- DIADE, University of Montpellier, IRD, CIRAD, Montpellier, France
| | - R Keith Slotkin
- Donald Danforth Plant Science Center, St. Louis, MO, 63132, USA
- Division of Biological Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - Frédéric Pontvianne
- Centre National de la Recherche Scientifique (CNRS), Laboratory of Plant Genome and Development, Perpignan, France
| | - Marco Catoni
- School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Marie Mirouze
- Institut de Recherche pour le Développement (IRD), Laboratory of Plant Genome and Development, Perpignan, France.
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France.
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4
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Liu P, Cuerda-Gil D, Shahid S, Slotkin RK. The Epigenetic Control of the Transposable Element Life Cycle in Plant Genomes and Beyond. Annu Rev Genet 2022; 56:63-87. [DOI: 10.1146/annurev-genet-072920-015534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Within the life cycle of a living organism, another life cycle exists for the selfish genome inhabitants, which are called transposable elements (TEs). These mobile sequences invade, duplicate, amplify, and diversify within a genome, increasing the genome's size and generating new mutations. Cells act to defend their genome, but rather than permanently destroying TEs, they use chromatin-level repression and epigenetic inheritance to silence TE activity. This level of silencing is ephemeral and reversible, leading to a dynamic equilibrium between TE suppression and reactivation within a host genome. The coexistence of the TE and host genome can also lead to the domestication of the TE to serve in host genome evolution and function. In this review, we describe the life cycle of a TE, with emphasis on how epigenetic regulation is harnessed to control TEs for host genome stability and innovation.
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Affiliation(s)
- Peng Liu
- Donald Danforth Plant Science Center, St. Louis, Missouri, USA
| | - Diego Cuerda-Gil
- Donald Danforth Plant Science Center, St. Louis, Missouri, USA
- Graduate Program in the Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, USA
| | - Saima Shahid
- Donald Danforth Plant Science Center, St. Louis, Missouri, USA
| | - R. Keith Slotkin
- Donald Danforth Plant Science Center, St. Louis, Missouri, USA
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, USA
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5
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Valli AA, Gonzalo-Magro I, Sanchez DH. Rearranged Endogenized Plant Pararetroviruses as Evidence of Heritable RNA-based Immunity. Mol Biol Evol 2022; 40:6794085. [PMID: 36322467 PMCID: PMC9868043 DOI: 10.1093/molbev/msac240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 09/05/2022] [Accepted: 10/25/2022] [Indexed: 01/24/2023] Open
Abstract
Eukaryotic genomics frequently revealed historical spontaneous endogenization events of external invading nucleic acids, such as viral elements. In plants, an extensive occurrence of endogenous plant pararetroviruses (EPRVs) is usually believed to endow hosts with an additional layer of internal suppressive weaponry. However, an actual demonstration of this activity remains speculative. We analyzed the EPRV component and accompanying silencing effectors of Solanum lycopersicum, documenting that intronic/intergenic pararetroviral integrations bearing inverted-repeats fuel the plant's RNA-based immune system with suitable transcripts capable of evoking a silencing response. A surprisingly small set of rearrangements explained a substantial fraction of pararetroviral-derived endogenous small-interfering (si)RNAs, enriched in 22-nt forms typically associated with anti-viral post-transcriptional gene silencing. We provide preliminary evidence that such genetic and immunological signals may be found in other species outside the genus Solanum. Based on molecular dating, bioinformatics, and empirical explorations, we propose that homology-dependent silencing emerging from particular immuno-competent rearranged chromosomal areas that constitute an adaptive heritable trans-acting record of past infections, with potential impact against the unlocking of plant latent EPRVs and cognate-free pararetroviruses.
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Affiliation(s)
| | - Irene Gonzalo-Magro
- Centro Nacional de Biotecnología (CNB-CSIC), Calle Darwin 3, 28049 Madrid, Spain
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Wang D, Yu C, Zhang J, Peterson T. Excision and reinsertion of Ac macrotransposons in maize. Genetics 2022; 221:iyac067. [PMID: 35471241 PMCID: PMC9339288 DOI: 10.1093/genetics/iyac067] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 04/18/2022] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic Macrotransposons (MTns) can be formed by 2 nearby elements flanking a segment of host DNA. The maize Ac transposon can form Ac::MTns, but little is known about Ac::MTn transposition activities. Here, we studied 3 Ac::MTns at the maize p1 locus, each of which is composed of a segment of maize p1 genomic DNA (up to 15 kb) bounded by a fractured Ac element (fAc, 2039 bp), and a full-length Ac element in direct orientation. The resulting Ac::MTns are of 16, 16.5, and 22 kb total length. From these 3 Ac::MTns, we identified 10 independent cases of macrotransposition, and observed similar features of transposition between Ac::MTn and standard Ac/Ds, including characteristic excision footprints and insertion target site duplications. Nine out of the 10 Ac::MTn reinsertion targets were genetically linked to the donor sites, another similarity with Ac/Ds standard transposition. We also identified a MTn-like structure in the maize B73 reference genome and 5 NAM founder lines. The MTn in diverse lines is flanked by target site duplications, confirming the historic occurrence of MTn transposition during genome evolution. Our results show that Ac::MTns are capable of mobilizing segments of DNA long enough to include a typical full-length plant gene and in theory could erode gene colinearity in syntenic regions during plant genome evolution.
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Affiliation(s)
- Dafang Wang
- Division of Math and Sciences, Delta State University, Cleveland, MS 38733-0001, USA
| | - Chuanhe Yu
- The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Jianbo Zhang
- Department of Horticultural Science, Mountain Horticultural Crops Research and Extension Center, North Carolina State University, Mills River, NC 28759, USA
| | - Thomas Peterson
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011-3260, USA
- Department of Agronomy, Iowa State University, Ames, IA 50011-3260, USA
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7
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Sasaki T, Ro K, Caillieux E, Manabe R, Bohl-Viallefond G, Baduel P, Colot V, Kakutani T, Quadrana L. Fast co-evolution of anti-silencing systems shapes the invasiveness of Mu-like DNA transposons in eudicots. EMBO J 2022; 41:e110070. [PMID: 35285528 PMCID: PMC9016345 DOI: 10.15252/embj.2021110070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 02/10/2022] [Accepted: 02/15/2022] [Indexed: 01/09/2023] Open
Abstract
Transposable elements (TEs) constitute a major threat to genome stability and are therefore typically silenced by epigenetic mechanisms. In response, some TEs have evolved counteracting systems to suppress epigenetic silencing. In the model plant Arabidopsis thaliana, two such anti-silencing systems have been identified and found to be mediated by the VANC DNA-binding proteins encoded by VANDAL transposons. Here, we show that anti-silencing systems have rapidly diversified since their origin in eudicots by gaining and losing VANC-containing domains, such as DUF1985, DUF287, and Ulp1, as well as target sequence motifs. We further demonstrate that these motifs determine anti-silencing specificity by sequence, density, and helical periodicity. Moreover, such rapid diversification yielded at least 10 distinct VANC-induced anti-silencing systems in Arabidopsis. Strikingly, anti-silencing of non-autonomous VANDALs, which can act as reservoirs of 24-nt small RNAs, is critical to prevent the demise of cognate autonomous TEs and to ensure their propagation. Our findings illustrate how complex co-evolutionary dynamics between TEs and host suppression pathways have shaped the emergence of new epigenetic control mechanisms.
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Affiliation(s)
- Taku Sasaki
- Department of Biological Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Kyudo Ro
- Department of Biological Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Erwann Caillieux
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Ecole Normale Supérieure, PSL Research University, Paris, France
| | - Riku Manabe
- Department of Biological Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Grégoire Bohl-Viallefond
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Ecole Normale Supérieure, PSL Research University, Paris, France
| | - Pierre Baduel
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Ecole Normale Supérieure, PSL Research University, Paris, France
| | - Vincent Colot
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Ecole Normale Supérieure, PSL Research University, Paris, France
| | - Tetsuji Kakutani
- Department of Biological Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Leandro Quadrana
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Ecole Normale Supérieure, PSL Research University, Paris, France
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8
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Sharma SP, Zuo T, Peterson T. Transposon-induced inversions activate gene expression in the maize pericarp. Genetics 2021; 218:iyab062. [PMID: 33905489 PMCID: PMC8225341 DOI: 10.1093/genetics/iyab062] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 04/09/2021] [Indexed: 11/28/2022] Open
Abstract
Chromosomal inversions can have considerable biological and agronomic impacts including disrupted gene function, change in gene expression, and inhibited recombination. Here, we describe the molecular structure and functional impact of six inversions caused by Alternative Transpositions between p1 and p2 genes responsible for floral pigmentation in maize. In maize line p1-wwB54, the p1 gene is null and the p2 gene is expressed in anther and silk but not in pericarp, making the kernels white. By screening for kernels with red pericarp, we identified inversions in this region caused by transposition of Ac and fractured Ac (fAc) transposable elements. We hypothesize that these inversions place the p2 gene promoter near a p1 gene enhancer, thereby activating p2 expression in kernel pericarp. To our knowledge, this is the first report of multiple recurrent inversions that change the position of a gene promoter relative to an enhancer to induce ectopic expression in a eukaryote.
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Affiliation(s)
- Sharu Paul Sharma
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Tao Zuo
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Thomas Peterson
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
- Department of Agronomy, Iowa State University, Ames, IA 50011, USA
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9
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Liu B, Iwata-Otsubo A, Yang D, Baker RL, Liang C, Jackson SA, Liu S, Ma J, Zhao M. Analysis of CACTA transposase genes unveils the mechanism of intron loss and distinct small RNA silencing pathways underlying divergent evolution of Brassica genomes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 105:34-48. [PMID: 33098166 DOI: 10.1111/tpj.15037] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 10/19/2020] [Accepted: 10/13/2020] [Indexed: 06/11/2023]
Abstract
In comparison with retrotransposons, DNA transposons make up a smaller proportion of most plant genomes. However, these elements are often proximal to genes to affect gene expression depending on the activity of the transposons, which is largely reflected by the activity of the transposase genes. Here, we show that three AT-rich introns were retained in the TNP2-like transposase genes of the Bot1 (Brassica oleracea transposon 1) CACTA transposable elements in Brassica oleracea, but were lost in the majority of the Bot1 elements in Brassica rapa. A recent burst of transposition of Bot1 was observed in B. oleracea, but not in B. rapa. This burst of transposition is likely related to the activity of the TNP2-like transposase genes as the expression values of the transposase genes were higher in B. oleracea than in B. rapa. In addition, distinct populations of small RNAs (21, 22 and 24 nt) were detected from the Bot1 elements in B. oleracea, but the vast majority of the small RNAs from the Bot1 elements in B. rapa are 24 nt in length. We hypothesize that the different activity of the TNP2-like transposase genes is likely associated with the three introns, and intron loss is likely reverse transcriptase mediated. Furthermore, we propose that the Bot1 family is currently undergoing silencing in B. oleracea, but has already been silenced in B. rapa. Taken together, our data provide new insights into the differentiation of transposons and their role in the asymmetric evolution of these two closely related Brassica species.
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Affiliation(s)
- Beibei Liu
- Department of Biology, Miami University, Oxford, OH, 45056, USA
| | - Aiko Iwata-Otsubo
- Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602,, USA
| | - Diya Yang
- Department of Biology, Miami University, Oxford, OH, 45056, USA
| | - Robert L Baker
- Department of Biology, Miami University, Oxford, OH, 45056, USA
| | - Chun Liang
- Department of Biology, Miami University, Oxford, OH, 45056, USA
| | - Scott A Jackson
- Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602,, USA
| | - Shengyi Liu
- Oil Crops Research Institute, Chinese Academy of Agricultural Sciences, Wuhan, 430062, China
| | - Jianxin Ma
- Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA
| | - Meixia Zhao
- Department of Biology, Miami University, Oxford, OH, 45056, USA
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10
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Su W, Zuo T, Peterson T. Ectopic Expression of a Maize Gene Is Induced by Composite Insertions Generated Through Alternative Transposition. Genetics 2020; 216:1039-1049. [PMID: 32988986 PMCID: PMC7768264 DOI: 10.1534/genetics.120.303592] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Accepted: 09/23/2020] [Indexed: 12/25/2022] Open
Abstract
Transposable elements (TEs) are DNA sequences that can mobilize and proliferate throughout eukaryotic genomes. Previous studies have shown that in plant genomes, TEs can influence gene expression in various ways, such as inserting in introns or exons to alter transcript structure and content, and providing novel promoters and regulatory elements to generate new regulatory patterns. Furthermore, TEs can also regulate gene expression at the epigenetic level by modifying chromatin structure, changing DNA methylation status, and generating small RNAs. In this study, we demonstrated that Ac/fractured Ac (fAc) TEs are able to induce ectopic gene expression by duplicating and shuffling enhancer elements. Ac/fAc elements belong to the hAT family of class II TEs. They can undergo standard transposition events, which involve the two termini of a single transposon, or alternative transposition events that involve the termini of two different nearby elements. Our previous studies have shown that alternative transposition can generate various genome rearrangements such as deletions, duplications, inversions, translocations, and composite insertions (CIs). We identified >50 independent cases of CIs generated by Ac/fAc alternative transposition and analyzed 10 of them in detail. We show that these CIs induced ectopic expression of the maize pericarp color 2 (p2) gene, which encodes a Myb-related protein. All the CIs analyzed contain sequences including a transcriptional enhancer derived from the nearby p1 gene, suggesting that the CI-induced activation of p2 is affected by mobilization of the p1 enhancer. This is further supported by analysis of a mutant in which the CI is excised and p2 expression is lost. These results show that alternative transposition events are not only able to induce genome rearrangements, but also generate CIs that can control gene expression.
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Affiliation(s)
- Weijia Su
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50011-3260
| | - Tao Zuo
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50011-3260
| | - Thomas Peterson
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50011-3260
- Department of Agronomy, Iowa State University, Ames, Iowa 50011-3260
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