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Duenas MA, Craig RJ, Gallaher SD, Moseley JL, Merchant SS. Leaky ribosomal scanning enables tunable translation of bicistronic ORFs in green algae. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.24.605010. [PMID: 39091764 PMCID: PMC11291117 DOI: 10.1101/2024.07.24.605010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/04/2024]
Abstract
Advances in sequencing technology have unveiled examples of nucleus-encoded polycistronic genes, once considered rare. Exclusively polycistronic transcripts are prevalent in green algae, although the mechanism by which multiple polypeptides are translated from a single transcript is unknown. Here, we used bioinformatic and in vivo mutational analyses to evaluate competing mechanistic models for polycistronic expression in green algae. High-confidence manually curated datasets of bicistronic loci from two divergent green algae, Chlamydomonas reinhardtii and Auxenochlorella protothecoides, revealed 1) a preference for weak Kozak-like sequences for ORF 1 and 2) an underrepresentation of potential initiation codons before ORF 2, which are suitable conditions for leaky scanning to allow ORF 2 translation. We used mutational analysis in Auxenochlorella protothecoides to test the mechanism. In vivo manipulation of the ORF 1 Kozak-like sequence and start codon altered reporter expression at ORF 2, with a weaker Kozak-like sequence enhancing expression and a stronger one diminishing it. A synthetic bicistronic dual reporter demonstrated inversely adjustable activity of green fluorescent protein expressed from ORF 1 and luciferase from ORF 2, depending on the strength of the ORF 1 Kozak-like sequence. Our findings demonstrate that translation of multiple ORFs in green algal bicistronic transcripts is consistent with episodic leaky ribosome scanning of ORF 1 to allow translation at ORF 2. This work has implications for the potential functionality of upstream open reading frames found across eukaryotic genomes and for transgene expression in synthetic biology applications.
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Affiliation(s)
- Marco A. Duenas
- Department of Plant and Microbial Biology, University of California Berkeley, University of California, Berkeley, CA 94720, USA
| | - Rory J. Craig
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
| | - Sean D. Gallaher
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Jeffrey L. Moseley
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
| | - Sabeeha S. Merchant
- Department of Plant and Microbial Biology, University of California Berkeley, University of California, Berkeley, CA 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology and Environmental Genomics and Systems Biology, Lawrence Berkeley National Laboratory, CA, USA
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2
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Gotsmann VL, Ting MKY, Haase N, Rudorf S, Zoschke R, Willmund F. Utilizing high-resolution ribosome profiling for the global investigation of gene expression in Chlamydomonas. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024; 117:1614-1634. [PMID: 38047591 DOI: 10.1111/tpj.16577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 11/20/2023] [Accepted: 11/22/2023] [Indexed: 12/05/2023]
Abstract
Ribosome profiling (Ribo-seq) is a powerful method for the deep analysis of translation mechanisms and regulatory circuits during gene expression. Extraction and sequencing of ribosome-protected fragments (RPFs) and parallel RNA-seq yields genome-wide insight into translational dynamics and post-transcriptional control of gene expression. Here, we provide details on the Ribo-seq method and the subsequent analysis with the unicellular model alga Chlamydomonas reinhardtii (Chlamydomonas) for generating high-resolution data covering more than 10 000 different transcripts. Detailed analysis of the ribosomal offsets on transcripts uncovers presumable transition states during translocation of elongating ribosomes within the 5' and 3' sections of transcripts and characteristics of eukaryotic translation termination, which are fundamentally distinct for chloroplast translation. In chloroplasts, a heterogeneous RPF size distribution along the coding sequence indicates specific regulatory phases during protein synthesis. For example, local accumulation of small RPFs correlates with local slowdown of psbA translation, possibly uncovering an uncharacterized regulatory step during PsbA/D1 synthesis. Further analyses of RPF distribution along specific cytosolic transcripts revealed characteristic patterns of translation elongation exemplified for the major light-harvesting complex proteins, LHCs. By providing high-quality datasets for all subcellular genomes and attaching our data to the Chlamydomonas reference genome, we aim to make ribosome profiles easily accessible for the broad research community. The data can be browsed without advanced bioinformatic background knowledge for translation output levels of specific genes and their splice variants and for monitoring genome annotation.
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Affiliation(s)
- Vincent Leon Gotsmann
- Molecular Genetics of Eukaryotes, RPTU Kaiserslautern-Landau, Paul-Ehrlich-Str. 23, 67663, Kaiserslautern, Germany
| | - Michael Kien Yin Ting
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
| | - Nadin Haase
- Institute of Cell Biology and Biophysics, Leibniz University Hanover, Herrenhäuser-Str. 2, 30419, Hanover, Germany
| | - Sophia Rudorf
- Institute of Cell Biology and Biophysics, Leibniz University Hanover, Herrenhäuser-Str. 2, 30419, Hanover, Germany
| | - Reimo Zoschke
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476, Potsdam-Golm, Germany
| | - Felix Willmund
- Molecular Genetics of Eukaryotes, RPTU Kaiserslautern-Landau, Paul-Ehrlich-Str. 23, 67663, Kaiserslautern, Germany
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3
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Wang L, Patena W, Van Baalen KA, Xie Y, Singer ER, Gavrilenko S, Warren-Williams M, Han L, Harrigan HR, Hartz LD, Chen V, Ton VTNP, Kyin S, Shwe HH, Cahn MH, Wilson AT, Onishi M, Hu J, Schnell DJ, McWhite CD, Jonikas MC. A chloroplast protein atlas reveals punctate structures and spatial organization of biosynthetic pathways. Cell 2023; 186:3499-3518.e14. [PMID: 37437571 DOI: 10.1016/j.cell.2023.06.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 05/06/2023] [Accepted: 06/11/2023] [Indexed: 07/14/2023]
Abstract
Chloroplasts are eukaryotic photosynthetic organelles that drive the global carbon cycle. Despite their importance, our understanding of their protein composition, function, and spatial organization remains limited. Here, we determined the localizations of 1,034 candidate chloroplast proteins using fluorescent protein tagging in the model alga Chlamydomonas reinhardtii. The localizations provide insights into the functions of poorly characterized proteins; identify novel components of nucleoids, plastoglobules, and the pyrenoid; and reveal widespread protein targeting to multiple compartments. We discovered and further characterized cellular organizational features, including eleven chloroplast punctate structures, cytosolic crescent structures, and unexpected spatial distributions of enzymes within the chloroplast. We also used machine learning to predict the localizations of other nuclear-encoded Chlamydomonas proteins. The strains and localization atlas developed here will serve as a resource to accelerate studies of chloroplast architecture and functions.
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Affiliation(s)
- Lianyong Wang
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Weronika Patena
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Kelly A Van Baalen
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Yihua Xie
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Emily R Singer
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Sophia Gavrilenko
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | | | - Linqu Han
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA; MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI 48824, USA
| | - Henry R Harrigan
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Linnea D Hartz
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Vivian Chen
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Vinh T N P Ton
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Saw Kyin
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Henry H Shwe
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Matthew H Cahn
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Alexandra T Wilson
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Masayuki Onishi
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Jianping Hu
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA; MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI 48824, USA
| | - Danny J Schnell
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Claire D McWhite
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Martin C Jonikas
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA.
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4
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Niemeyer J, Fischer L, Aylward FO, Schroda M. Analysis of Viral Promoters for Transgene Expression and of the Effect of 5'-UTRs on Alternative Translational Start Sites in Chlamydomonas. Genes (Basel) 2023; 14:genes14040948. [PMID: 37107706 PMCID: PMC10138193 DOI: 10.3390/genes14040948] [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: 03/14/2023] [Revised: 04/15/2023] [Accepted: 04/19/2023] [Indexed: 04/29/2023] Open
Abstract
Microalgae biotechnology has the potential to produce high quality bioproducts in a sustainable manner. Here, Chlamydomonas reinhardtii has shown great potential as a host for biotechnological exploitation. However, low expression of nuclear transgenes is still a problem and needs to be optimized. In many model organisms, viral promoters are used to drive transgene expression at high levels. However, no viruses are known to infect Chlamydomonas, and known viral promoters are not functional. Recently, two different lineages of giant viruses were identified in the genomes of Chlamydomonas reinhardtii field isolates. In this work, we tested six potentially strong promoters from these viral genomes for their ability to drive transgene expression in Chlamydomonas. We used ble, NanoLUC, and mCherry as reporter genes, and three native benchmark promoters as controls. None of the viral promoters drove expression of any reporter gene beyond background. During our study, we found that mCherry variants are produced by alternative in-frame translational start sites in Chlamydomonas. We show that this problem can be overcome by mutating the responsible methionine codons to codons for leucine and by using the 5'-UTR of βTUB2 instead of the 5'-UTRs of PSAD or RBCS2. Apparently, the βTUB2 5'-UTR promotes the use of the first start codon. This could be mediated by the formation of a stem-loop between sequences of the βTUB2 5'-UTR and sequences downstream of the first AUG in the mCherry reporter, potentially increasing the dwell time of the scanning 40S subunit on the first AUG and thus decreasing the probability of leaky scanning.
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Affiliation(s)
- Justus Niemeyer
- Molecular Biotechnology & Systems Biology, RPTU Kaiserslautern-Landau, Paul-Ehrlich-Straße 23, 67663 Kaiserslautern, Germany
| | - Laura Fischer
- Molecular Biotechnology & Systems Biology, RPTU Kaiserslautern-Landau, Paul-Ehrlich-Straße 23, 67663 Kaiserslautern, Germany
| | | | - Michael Schroda
- Molecular Biotechnology & Systems Biology, RPTU Kaiserslautern-Landau, Paul-Ehrlich-Straße 23, 67663 Kaiserslautern, Germany
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5
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Craig RJ, Gallaher SD, Shu S, Salomé PA, Jenkins JW, Blaby-Haas CE, Purvine SO, O’Donnell S, Barry K, Grimwood J, Strenkert D, Kropat J, Daum C, Yoshinaga Y, Goodstein DM, Vallon O, Schmutz J, Merchant SS. The Chlamydomonas Genome Project, version 6: Reference assemblies for mating-type plus and minus strains reveal extensive structural mutation in the laboratory. THE PLANT CELL 2023; 35:644-672. [PMID: 36562730 PMCID: PMC9940879 DOI: 10.1093/plcell/koac347] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 10/12/2022] [Accepted: 12/16/2022] [Indexed: 05/20/2023]
Abstract
Five versions of the Chlamydomonas reinhardtii reference genome have been produced over the last two decades. Here we present version 6, bringing significant advances in assembly quality and structural annotations. PacBio-based chromosome-level assemblies for two laboratory strains, CC-503 and CC-4532, provide resources for the plus and minus mating-type alleles. We corrected major misassemblies in previous versions and validated our assemblies via linkage analyses. Contiguity increased over ten-fold and >80% of filled gaps are within genes. We used Iso-Seq and deep RNA-seq datasets to improve structural annotations, and updated gene symbols and textual annotation of functionally characterized genes via extensive manual curation. We discovered that the cell wall-less classical reference strain CC-503 exhibits genomic instability potentially caused by deletion of the helicase RECQ3, with major structural mutations identified that affect >100 genes. We therefore present the CC-4532 assembly as the primary reference, although this strain also carries unique structural mutations and is experiencing rapid proliferation of a Gypsy retrotransposon. We expect all laboratory strains to harbor gene-disrupting mutations, which should be considered when interpreting and comparing experimental results. Collectively, the resources presented here herald a new era of Chlamydomonas genomics and will provide the foundation for continued research in this important reference organism.
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Affiliation(s)
- Rory J Craig
- California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720, USA
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Sean D Gallaher
- California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720, USA
| | - Shengqiang Shu
- United States Department of Energy, Joint Genome Institute, Berkeley, California 94720, USA
| | - Patrice A Salomé
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
- Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095, USA
| | - Jerry W Jenkins
- HudsonAlpha Genome Sequencing Center, HudsonAlpha Institute for Biotechnology, Huntsville, Alabama 35806, USA
| | - Crysten E Blaby-Haas
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Samuel O Purvine
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
| | - Samuel O’Donnell
- Laboratory of Computational and Quantitative Biology, UMR 7238, CNRS, Institut de Biologie Paris-Seine, Sorbonne Université, Paris 75005, France
| | - Kerrie Barry
- United States Department of Energy, Joint Genome Institute, Berkeley, California 94720, USA
| | - Jane Grimwood
- HudsonAlpha Genome Sequencing Center, HudsonAlpha Institute for Biotechnology, Huntsville, Alabama 35806, USA
| | - Daniela Strenkert
- California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720, USA
| | - Janette Kropat
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
| | - Chris Daum
- United States Department of Energy, Joint Genome Institute, Berkeley, California 94720, USA
| | - Yuko Yoshinaga
- United States Department of Energy, Joint Genome Institute, Berkeley, California 94720, USA
| | - David M Goodstein
- United States Department of Energy, Joint Genome Institute, Berkeley, California 94720, USA
| | - Olivier Vallon
- Unité Mixte de Recherche 7141, CNRS, Institut de Biologie Physico-Chimique, Sorbonne Université, Paris 75005, France
| | - Jeremy Schmutz
- United States Department of Energy, Joint Genome Institute, Berkeley, California 94720, USA
- HudsonAlpha Genome Sequencing Center, HudsonAlpha Institute for Biotechnology, Huntsville, Alabama 35806, USA
| | - Sabeeha S Merchant
- California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA
- Division of Environmental Genomics and Systems Biology, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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6
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Abstract
Historically, it has been understood that for gene expression in eukaryotes, each messenger RNA encodes a single protein. With the recent development of technologies to sequence full-length transcripts en masse, we have discovered hundreds of examples in two species of green algae where two, three, or more proteins are translated from a single transcript. These “polycistronic” transcripts are found in diverse species throughout the green algal lineage, which highlights their biological importance. We have leveraged these findings to coexpress pairs of genes on polycistronic transcripts in vitro, which should facilitate efforts to engineer algae for research and industrial applications. Polycistronic gene expression, common in prokaryotes, was thought to be extremely rare in eukaryotes. The development of long-read sequencing of full-length transcript isomers (Iso-Seq) has facilitated a reexamination of that dogma. Using Iso-Seq, we discovered hundreds of examples of polycistronic expression of nuclear genes in two divergent species of green algae: Chlamydomonas reinhardtii and Chromochloris zofingiensis. Here, we employ a range of independent approaches to validate that multiple proteins are translated from a common transcript for hundreds of loci. A chromatin immunoprecipitation analysis using trimethylation of lysine 4 on histone H3 marks confirmed that transcription begins exclusively at the upstream gene. Quantification of polyadenylated [poly(A)] tails and poly(A) signal sequences confirmed that transcription ends exclusively after the downstream gene. Coexpression analysis found nearly perfect correlation for open reading frames (ORFs) within polycistronic loci, consistent with expression in a shared transcript. For many polycistronic loci, terminal peptides from both ORFs were identified from proteomics datasets, consistent with independent translation. Synthetic polycistronic gene pairs were transcribed and translated in vitro to recapitulate the production of two distinct proteins from a common transcript. The relative abundance of these two proteins can be modified by altering the Kozak-like sequence of the upstream gene. Replacement of the ORFs with selectable markers or reporters allows production of such heterologous proteins, speaking to utility in synthetic biology approaches. Conservation of a significant number of polycistronic gene pairs between C. reinhardtii, C. zofingiensis, and five other species suggests that this mechanism may be evolutionarily ancient and biologically important in the green algal lineage.
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7
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Emrich-Mills TZ, Yates G, Barrett J, Girr P, Grouneva I, Lau CS, Walker CE, Kwok TK, Davey JW, Johnson MP, Mackinder LCM. A recombineering pipeline to clone large and complex genes in Chlamydomonas. THE PLANT CELL 2021; 33:1161-1181. [PMID: 33723601 PMCID: PMC8633747 DOI: 10.1093/plcell/koab024] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 01/18/2021] [Indexed: 05/10/2023]
Abstract
The ability to clone genes has greatly advanced cell and molecular biology research, enabling researchers to generate fluorescent protein fusions for localization and confirm genetic causation by mutant complementation. Most gene cloning is polymerase chain reaction (PCR)�or DNA synthesis-dependent, which can become costly and technically challenging as genes increase in size, particularly if they contain complex regions. This has been a long-standing challenge for the Chlamydomonas reinhardtii research community, as this alga has a high percentage of genes containing complex sequence structures. Here we overcame these challenges by developing a recombineering pipeline for the rapid parallel cloning of genes from a Chlamydomonas bacterial artificial chromosome collection. To generate fluorescent protein fusions for localization, we applied the pipeline at both batch and high-throughput scales to 203 genes related to the Chlamydomonas CO2 concentrating mechanism (CCM), with an overall cloning success rate of 77%. Cloning success was independent of gene size and complexity, with cloned genes as large as 23 kb. Localization of a subset of CCM targets confirmed previous mass spectrometry data, identified new pyrenoid components, and enabled complementation of mutants. We provide vectors and detailed protocols to facilitate easy adoption of this technology, which we envision will open up new possibilities in algal and plant research.
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Affiliation(s)
- Tom Z Emrich-Mills
- Department of Biology, University of York, York YO10 5DD, UK
- Department Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Gary Yates
- Department of Biology, University of York, York YO10 5DD, UK
| | - James Barrett
- Department of Biology, University of York, York YO10 5DD, UK
| | - Philipp Girr
- Department of Biology, University of York, York YO10 5DD, UK
| | - Irina Grouneva
- Department of Biology, University of York, York YO10 5DD, UK
| | - Chun Sing Lau
- Department of Biology, University of York, York YO10 5DD, UK
| | | | - Tsz Kam Kwok
- Department of Biology, University of York, York YO10 5DD, UK
| | - John W Davey
- Department of Biology, University of York, York YO10 5DD, UK
| | - Matthew P Johnson
- Department Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Luke C M Mackinder
- Department of Biology, University of York, York YO10 5DD, UK
- Author for correspondence: (L.C.M.M.)
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8
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Craig RJ, Hasan AR, Ness RW, Keightley PD. Comparative genomics of Chlamydomonas. THE PLANT CELL 2021; 33:1016-1041. [PMID: 33793842 PMCID: PMC8226300 DOI: 10.1093/plcell/koab026] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 01/22/2021] [Indexed: 05/06/2023]
Abstract
Despite its role as a reference organism in the plant sciences, the green alga Chlamydomonas reinhardtii entirely lacks genomic resources from closely related species. We present highly contiguous and well-annotated genome assemblies for three unicellular C. reinhardtii relatives: Chlamydomonas incerta, Chlamydomonas schloesseri, and the more distantly related Edaphochlamys debaryana. The three Chlamydomonas genomes are highly syntenous with similar gene contents, although the 129.2 Mb C. incerta and 130.2 Mb C. schloesseri assemblies are more repeat-rich than the 111.1 Mb C. reinhardtii genome. We identify the major centromeric repeat in C. reinhardtii as a LINE transposable element homologous to Zepp (the centromeric repeat in Coccomyxa subellipsoidea) and infer that centromere locations and structure are likely conserved in C. incerta and C. schloesseri. We report extensive rearrangements, but limited gene turnover, between the minus mating type loci of these Chlamydomonas species. We produce an eight-species core-Reinhardtinia whole-genome alignment, which we use to identify several hundred false positive and missing genes in the C. reinhardtii annotation and >260,000 evolutionarily conserved elements in the C. reinhardtii genome. In summary, these resources will enable comparative genomics analyses for C. reinhardtii, significantly extending the analytical toolkit for this emerging model system.
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Affiliation(s)
| | - Ahmed R Hasan
- Department of Biology, University of Toronto Mississauga, Mississauga, Onatrio, Canada L5L 1C6
| | - Rob W Ness
- Department of Biology, University of Toronto Mississauga, Mississauga, Onatrio, Canada L5L 1C6
| | - Peter D Keightley
- School of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, EH9 3FL Edinburgh, UK
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9
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Yu F, Wang L, Li W, Lu L. Identification of a novel membrane-associated protein from the S7 segment of grass carp reovirus. J Gen Virol 2019; 100:369-379. [PMID: 30688636 DOI: 10.1099/jgv.0.001223] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Aquareovirus is a genus of viruses in family Reoviridae, subfamily Spinareovirinae, members of which infect fish, shellfish and crustaceans. Grass carp reovirus (GCRV), a genotype 1 reovirus isolated from grass carp, has served as a model strain for investigating aquareovirus-host interactions. Herein, we report a neglected open reading frame (ORF), tentatively named NS12, residing between NS16 and NS31 in segment 7 (S7) of the virus genome. With an additional reading frame, the nucleotide sequence of NS12 partially overlaps with the 3' expressible nucleotide sequence of NS16. NS12 is not a pseudogene during virus replication, as confirmed in fish cells infected with GCRV and based on amino acid sequence analysis and protein expression pattern. Bioinformatics analysis indicated that NS12 is a transmembrane protein, which was confirmed by its exclusive presence in the membrane-associated fraction of the cell lysate. However, unlike fusion protein NS16, NS12 alone could not induce visible syncytium formation in fish cells. Thus, NS12 is functionally distinct from known aquareovirus membrane-associated protein NS16. NS12-like ORFs (with an AUG or non-AUG initiator codon) are also present in the S7 segment of other aquareoviruses, suggesting that NS12 homologues may be widely distributed in the genus Aquareovirus.
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Affiliation(s)
- Fei Yu
- 1National Pathogen Collection Center for Aquatic Animals, Shanghai Ocean University, Shanghai, PR China
| | - Longlong Wang
- 2Key Laboratory of Agriculture Ministry for Freshwater Aquatic Genetic Resources, Shanghai Ocean University, Shanghai, PR China
| | - Wanjuan Li
- 3National Experimental Teaching Demonstration Center for Fishery Sciences, Shanghai Ocean University, Shanghai, PR China
| | - Liqun Lu
- 1National Pathogen Collection Center for Aquatic Animals, Shanghai Ocean University, Shanghai, PR China
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10
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Breker M, Lieberman K, Cross FR. Comprehensive Discovery of Cell-Cycle-Essential Pathways in Chlamydomonas reinhardtii. THE PLANT CELL 2018; 30:1178-1198. [PMID: 29743196 PMCID: PMC6048789 DOI: 10.1105/tpc.18.00071] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/26/2018] [Accepted: 05/08/2018] [Indexed: 05/05/2023]
Abstract
We generated a large collection of temperature-sensitive lethal mutants in the unicellular green alga Chlamydomonas reinhardtii, focusing on mutations specifically affecting cell cycle regulation. We used UV mutagenesis and robotically assisted phenotypic screening to isolate candidates. To overcome the bottleneck at the critical step of molecular identification of the causative mutation ("driver"), we developed MAPS-SEQ (meiosis-assisted purifying selection sequencing), a multiplexed genetic/bioinformatics strategy. MAPS-SEQ allowed us to perform multiplexed simultaneous determination of the driver mutations from hundreds of neutral "passenger" mutations in each member of a large pool of mutants. This method should work broadly, including in multicellular diploid genetic systems, for any scorable trait. Using MAPS-SEQ, we identified essential genes spanning a wide range of molecular functions. Phenotypic clustering based on DNA content analysis and cell morphology indicated that the mutated genes function in the cell cycle at multiple points and by diverse mechanisms. The collection is sufficiently complete to allow specific conditional inactivation of almost all cell-cycle-regulatory pathways. Approximately seventy-five percent of the essential genes identified in this project had clear orthologs in land plant genomes, a huge enrichment compared with the value of ∼20% for the Chlamydomonas genome overall. Findings about these mutants will likely have direct relevance to essential cell biology in land plants.
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Affiliation(s)
- Michal Breker
- Laboratory of Cell Cycle Genetics, The Rockefeller University, New York, New York 10065
| | - Kristi Lieberman
- Laboratory of Cell Cycle Genetics, The Rockefeller University, New York, New York 10065
| | - Frederick R Cross
- Laboratory of Cell Cycle Genetics, The Rockefeller University, New York, New York 10065
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11
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Mackinder LCM, Chen C, Leib RD, Patena W, Blum SR, Rodman M, Ramundo S, Adams CM, Jonikas MC. A Spatial Interactome Reveals the Protein Organization of the Algal CO 2-Concentrating Mechanism. Cell 2017; 171:133-147.e14. [PMID: 28938113 PMCID: PMC5616186 DOI: 10.1016/j.cell.2017.08.044] [Citation(s) in RCA: 160] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 06/30/2017] [Accepted: 08/22/2017] [Indexed: 11/20/2022]
Abstract
Approximately one-third of global CO2 fixation is performed by eukaryotic algae. Nearly all algae enhance their carbon assimilation by operating a CO2-concentrating mechanism (CCM) built around an organelle called the pyrenoid, whose protein composition is largely unknown. Here, we developed tools in the model alga Chlamydomonas reinhardtii to determine the localizations of 135 candidate CCM proteins and physical interactors of 38 of these proteins. Our data reveal the identity of 89 pyrenoid proteins, including Rubisco-interacting proteins, photosystem I assembly factor candidates, and inorganic carbon flux components. We identify three previously undescribed protein layers of the pyrenoid: a plate-like layer, a mesh layer, and a punctate layer. We find that the carbonic anhydrase CAH6 is in the flagella, not in the stroma that surrounds the pyrenoid as in current models. These results provide an overview of proteins operating in the eukaryotic algal CCM, a key process that drives global carbon fixation.
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Affiliation(s)
- Luke C M Mackinder
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Chris Chen
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA; Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Ryan D Leib
- Stanford University Mass Spectrometry, Stanford University, Stanford, CA 94305, USA
| | - Weronika Patena
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Sean R Blum
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Matthew Rodman
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Silvia Ramundo
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA
| | - Christopher M Adams
- Stanford University Mass Spectrometry, Stanford University, Stanford, CA 94305, USA
| | - Martin C Jonikas
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA; Department of Biology, Stanford University, Stanford, CA 94305, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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Abstract
In many contexts, the problem arises of determining which of many candidate mutations is the most likely to be causative for some phenotype. It is desirable to have a way to evaluate this probability that relies as little as possible on previous knowledge, to avoid bias against discovering new genes or functions. We have isolated mutants with blocked cell cycle progression in Chlamydomonas and determined mutant genome sequences. Due to the intensity of UV mutagenesis required for efficient mutant collection, the mutants contain multiple mutations altering coding sequence. To provide a quantitative estimate of probability that each individual mutation in a given mutant is the causative one, we developed a Bayesian approach. The approach employs four independent indicators: sequence conservation of the mutated coding sequence with Arabidopsis; severity of the mutation relative to Chlamydomonas wild-type based on Blosum62 scores; meiotic mapping information for location of the causative mutation relative to known molecular markers; and, for a subset of mutants, the transcriptional profile of the candidate wild-type genes through the mitotic cell cycle. These indicators are statistically independent, and so can be combined quantitatively into a single probability calculation. We validate this calculation: recently isolated mutations that were not in the training set for developing the indicators, with high calculated probability of causality, are confirmed in every case by additional genetic data to indeed be causative. Analysis of “best reciprocal BLAST” (BRB) relationships among Chlamydomonas and other eukaryotes indicate that the temperature sensitive-lethal (Ts-lethal) mutants that our procedure recovers are highly enriched for fundamental cell-essential functions conserved broadly across plants and other eukaryotes, accounting for the high information content of sequence alignment to Arabidopsis.
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Robust Transgene Expression from Bicistronic mRNA in the Green Alga Chlamydomonas reinhardtii. G3-GENES GENOMES GENETICS 2016; 6:4115-4125. [PMID: 27770025 PMCID: PMC5144980 DOI: 10.1534/g3.116.033035] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The unicellular green alga Chlamydomonas reinhardtii is a model organism that provides an opportunity to understand the evolution and functional biology of the lineage that includes the land plants, as well as aspects of the fundamental core biology conserved throughout the eukaryotic phylogeny. Although many tools are available to facilitate genetic, molecular biological, biochemical, and cell biological studies in Chlamydomonas, expression of unselected transgenes of interest (GOIs) has been challenging. In most methods used previously, the GOI and a selectable marker are expressed from two separate mRNAs, so that their concomitant expression is not guaranteed. In this study, we developed constructs that allow expression of an upstream GOI and downstream selectable marker from a single bicistronic mRNA. Although this approach in other systems has typically required a translation-enhancing element such as an internal ribosome entry site for the downstream marker, we found that a short stretch of unstructured junction sequence was sufficient to obtain adequate expression of the downstream gene, presumably through post-termination reinitiation. With this system, we obtained robust expression of both endogenous and heterologous GOIs, including fluorescent proteins and tagged fusion proteins, in the vast majority of transformants, thus eliminating the need for tedious secondary screening for GOI-expressing transformants. This improved efficiency should greatly facilitate a variety of genetic and cell-biological studies in Chlamydomonas and also enable new applications such as expression-based screens and large-scale production of foreign proteins.
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Abstract
The Chlamydomonas genome has been sequenced, assembled, and annotated to produce a rich resource for genetics and molecular biology in this well-studied model organism. However, the current reference genome contains ∼1000 blocks of unknown sequence (‘N-islands’), which are frequently placed in introns of annotated gene models. We developed a strategy to search for previously unknown exons hidden within such blocks, and determine the sequence, and exon/intron boundaries, of such exons. These methods are based on assembly and alignment of short cDNA and genomic DNA reads, completely independent of prior reference assembly or annotation. Our evidence indicates that a substantial proportion of the annotated intronic N-islands contain hidden exons. For most of these, our algorithm recovers full exonic sequence with associated splice junctions and exon-adjacent intronic sequence. These new exons represent de novo sequence generally present nowhere in the assembled genome, and the added sequence improves evolutionary conservation of the predicted encoded peptides.
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