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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: 14] [Impact Index Per Article: 14.0] [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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Shi Y, Luo C, Xiang Y, Qian D. Rab GTPases, tethers, and SNAREs work together to regulate Arabidopsis cell plate formation. FRONTIERS IN PLANT SCIENCE 2023; 14:1120841. [PMID: 36844074 PMCID: PMC9950755 DOI: 10.3389/fpls.2023.1120841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 01/30/2023] [Indexed: 06/18/2023]
Abstract
Cell plates are transient structures formed by the fusion of vesicles at the center of the dividing plane; furthermore, these are precursors to new cell walls and are essential for cytokinesis. Cell plate formation requires a highly coordinated process of cytoskeletal rearrangement, vesicle accumulation and fusion, and membrane maturation. Tethering factors have been shown to interact with the Ras superfamily of small GTP binding proteins (Rab GTPases) and soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), which are essential for cell plate formation during cytokinesis and are fundamental for maintaining normal plant growth and development. In Arabidopsis thaliana, members of the Rab GTPases, tethers, and SNAREs are localized in cell plates, and mutations in the genes encoding these proteins result in typical cytokinesis-defective phenotypes, such as the formation of abnormal cell plates, multinucleated cells, and incomplete cell walls. This review highlights recent findings on vesicle trafficking during cell plate formation mediated by Rab GTPases, tethers, and SNAREs.
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A Preliminary Study on the Mechanisms of Growth and Physiological Changes in Response to Different Temperatures in Neopyropia yezoensis (Rhodophyta). WATER 2022. [DOI: 10.3390/w14142175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
As an economically valuable red seaweed, Neopyropia yezoensis (Rhodophyta) is cultivated in intertidal areas, and its growth and development are greatly influenced by environmental factors such as temperature. Although much effort has been devoted to delineating the influence, the underlying cellular and molecular mechanisms remain elusive. In this study, the gametophyte blades and protoplasts were cultured at different temperatures (13 °C, 17 °C, 21 °C, 25 °C). Only blades cultured at 13 °C maintained a normal growth state (the relative growth rate of thalli was positive, and the content of phycobiliprotein and pigments changed little); the survival and division rates of protoplasts were high at 13 °C, but greatly decreased with the increase in temperature, suggesting that 13 °C is suitable for the growth of N. yezoensis. In our efforts to delineate the underlying mechanism, a partial coding sequence (CDS) of Cyclin B and the complete CDS of cyclin-dependent-kinase B (CDKB) in N. yezoensis were cloned. Since Cyclin B controls G2/M phase transition by activating CDK and regulates the progression of cell division, we then analyzed how Cyclin B expression in the gametophyte blades might change with temperatures by qPCR and Western blotting. The results showed that the expression of Cyclin B first increased and then decreased after transfer from 13 °C to higher temperatures, and the downregulation of Cyclin B was more obvious with the increase in temperature. The phosphorylation of extracellular signal-regulated kinase (ERK) decreased with the increase in temperature, suggesting inactivation of ERK at higher temperatures; inhibition of ERK by FR180204 significantly decreased the survival and division rates of protoplasts cultured at 13 °C. These results suggest that downregulation of Cyclin B and inactivation of ERK might be involved in negatively regulating the survival and division of protoplasts and the growth of gametophyte blades of N. yezoensis at high temperatures.
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Zhang N, Mattoon EM, McHargue W, Venn B, Zimmer D, Pecani K, Jeong J, Anderson CM, Chen C, Berry JC, Xia M, Tzeng SC, Becker E, Pazouki L, Evans B, Cross F, Cheng J, Czymmek KJ, Schroda M, Mühlhaus T, Zhang R. Systems-wide analysis revealed shared and unique responses to moderate and acute high temperatures in the green alga Chlamydomonas reinhardtii. Commun Biol 2022; 5:460. [PMID: 35562408 PMCID: PMC9106746 DOI: 10.1038/s42003-022-03359-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 04/12/2022] [Indexed: 12/15/2022] Open
Abstract
Different intensities of high temperatures affect the growth of photosynthetic cells in nature. To elucidate the underlying mechanisms, we cultivated the unicellular green alga Chlamydomonas reinhardtii under highly controlled photobioreactor conditions and revealed systems-wide shared and unique responses to 24-hour moderate (35°C) and acute (40°C) high temperatures and subsequent recovery at 25°C. We identified previously overlooked unique elements in response to moderate high temperature. Heat at 35°C transiently arrested the cell cycle followed by partial synchronization, up-regulated transcripts/proteins involved in gluconeogenesis/glyoxylate-cycle for carbon uptake and promoted growth. But 40°C disrupted cell division and growth. Both high temperatures induced photoprotection, while 40°C distorted thylakoid/pyrenoid ultrastructure, affected the carbon concentrating mechanism, and decreased photosynthetic efficiency. We demonstrated increased transcript/protein correlation during both heat treatments and hypothesize reduced post-transcriptional regulation during heat may help efficiently coordinate thermotolerance mechanisms. During recovery after both heat treatments, especially 40°C, transcripts/proteins related to DNA synthesis increased while those involved in photosynthetic light reactions decreased. We propose down-regulating photosynthetic light reactions during DNA replication benefits cell cycle resumption by reducing ROS production. Our results provide potential targets to increase thermotolerance in algae and crops. A systems-wide analysis of the single-cell green alga Chlamydomonas reinhardti reveals shared and unique responses to moderate and acute high temperatures using multiple-level investigation of transcriptomics, proteomics, cell physiology, photosynthetic parameters, and cellular ultrastructure.
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Affiliation(s)
- Ningning Zhang
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | - Erin M Mattoon
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA.,Plant and Microbial Biosciences Program, Division of Biology and Biomedical Sciences, Washington University in Saint Louis, St. Louis, Missouri, 63130, USA
| | - Will McHargue
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA.,Plant and Microbial Biosciences Program, Division of Biology and Biomedical Sciences, Washington University in Saint Louis, St. Louis, Missouri, 63130, USA
| | | | - David Zimmer
- TU Kaiserslautern, Kaiserslautern, 67663, Germany
| | - Kresti Pecani
- The Rockefeller University, New York, New York, 10065, USA
| | - Jooyeon Jeong
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | - Cheyenne M Anderson
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA.,Plant and Microbial Biosciences Program, Division of Biology and Biomedical Sciences, Washington University in Saint Louis, St. Louis, Missouri, 63130, USA
| | - Chen Chen
- University of Missouri-Columbia, Columbia, Missouri, 65211, USA
| | - Jeffrey C Berry
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | - Ming Xia
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | - Shin-Cheng Tzeng
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | - Eric Becker
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | - Leila Pazouki
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | - Bradley Evans
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | - Fred Cross
- The Rockefeller University, New York, New York, 10065, USA
| | - Jianlin Cheng
- University of Missouri-Columbia, Columbia, Missouri, 65211, USA
| | - Kirk J Czymmek
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA
| | | | | | - Ru Zhang
- Donald Danforth Plant Science Center, St. Louis, Missouri, 63132, USA.
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5
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Lin YT, Takeuchi T, Youk B, Umen J, Sears BB, Benning C. Chlamydomonas CHT7 is involved in repressing DNA replication and mitotic genes during synchronous growth. G3 GENES|GENOMES|GENETICS 2022; 12:6523978. [PMID: 35137070 PMCID: PMC8895990 DOI: 10.1093/g3journal/jkac023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 01/21/2022] [Indexed: 11/13/2022]
Abstract
In the green alga Chlamydomonas reinhardtii, regulation of the cell cycle in response to external cues is critical for survival in a changing environment. The loss of the nuclear COMPROMISED HYDROLYSIS OF TRIACYLGLYCEROLS 7 (CHT7) protein affects the expression of many genes especially in response to nitrogen availability. Cells lacking CHT7 exhibit abnormal cell morphology following nitrogen deprivation and fail to resume normal cell division after N resupply. To investigate the function of CHT7 in the regulation of cell cycle-related pathways, cells were synchronized, and RNA-seq analysis was performed during various stages of the cell cycle. In the cht7 mutant following nitrogen deprivation, the cells were not dividing, but a subset of cell cycle genes involved in DNA replication and mitosis were found to be derepressed, suggesting that the CHT7 protein plays a role in cell cycle regulation that is opposite to that of the mitotic cyclin-dependent kinases. Furthermore, genes for cell wall synthesis and remodeling were found to be abnormally induced in nondividing cht7 cells; this misregulation may deplete cellular resources and thus contribute to cell death following nitrogen deprivation. Lastly, 43 minimally characterized kinases were found to be highly misregulated in cht7. Further analysis suggested that some of these CHT7-regulated kinases may be related to the MAP3K and Aurora-like kinases, while others are unique. Together, these results suggest a role of CHT7 in transcriptional regulation of the cell cycle and reveal several pathways and genes whose expression appears to be subject to a CHT7-mediated regulatory network.
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Affiliation(s)
- Yang-Tsung Lin
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
| | - Tomomi Takeuchi
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
| | - Brian Youk
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - James Umen
- Donald Danforth Plant Science Center, St. Louis, MO 63132, USA
| | - Barbara B Sears
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Christoph Benning
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
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6
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Ng LM, Komaki S, Takahashi H, Yamano T, Fukuzawa H, Hashimoto T. Hyperosmotic stress-induced microtubule disassembly in Chlamydomonas reinhardtii. BMC PLANT BIOLOGY 2022; 22:46. [PMID: 35065609 PMCID: PMC8783414 DOI: 10.1186/s12870-022-03439-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Land plants respond to drought and salinity by employing multitude of sophisticated mechanisms with physiological and developmental consequences. Abscisic acid-mediated signaling pathways have evolved as land plant ancestors explored their habitats toward terrestrial dry area, and now play major roles in hyperosmotic stress responses in flowering plants. Green algae living in fresh water habitat do not possess abscisic acid signaling pathways but need to cope with increasing salt concentrations or high osmolarity when challenged with adverse aquatic environment. Hyperosmotic stress responses in green algae are largely unexplored. RESULTS In this study, we characterized hyperosmotic stress-induced cytoskeletal responses in Chlamydomonas reinhardtii, a fresh water green algae. The Chlamydomonas PROPYZAMIDE-HYPERSENSITEVE 1 (PHS1) tubulin kinase quickly and transiently phosphorylated a large proportion of cellular α-tubulin at Thr349 in G1 phase and during mitosis, which resulted in transient disassembly of microtubules, when challenged with > 0.2 M sorbitol or > 0.1 M NaCl. By using phs1 loss-of-function algal mutant cells, we demonstrated that transient microtubule destabilization by sorbitol did not affect cell growth in G1 phase but delayed mitotic cell cycle progression. Genome sequence analyses indicate that PHS1 genes evolved in ancestors of the Chlorophyta. Interestingly, PHS1 genes are present in all sequenced genomes of freshwater Chlorophyta green algae (including Chlamydomonas) but are absent in some marine algae of this phylum. CONCLUSION PHS1-mediated tubulin phosphorylation was found to be partly responsible for the efficient stress-responsive mitotic delay in Chlamydomonas cells. Ancient hyperosmotic stress-triggered cytoskeletal remodeling responses thus emerged when the PHS1 tubulin kinase gene evolved in freshwater green algae.
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Affiliation(s)
- Lee Mei Ng
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192, Japan
| | - Shinichiro Komaki
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192, Japan
| | - Hideyuki Takahashi
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192, Japan
| | - Takashi Yamano
- Graduate School of Biostudies, Kyoto University, Kyoto, Kyoto, 606-8502, Japan
| | - Hideya Fukuzawa
- Graduate School of Biostudies, Kyoto University, Kyoto, Kyoto, 606-8502, Japan
| | - Takashi Hashimoto
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192, Japan.
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7
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Assaying Cyclin-Dependent Kinase Activity in Synchronized Algal Cultures. Methods Mol Biol 2021. [PMID: 34705233 DOI: 10.1007/978-1-0716-1744-1_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Cyclin-dependent kinases (CDKs) are key regulators of the cell cycle in eukaryotes. Assessing their activity is one of the basic methods used to analyze their function. This is particularly true in synchronized cultures of unicellular organisms, where the entire culture is in the same physiological state. In this chapter, I describe a simple biochemical method to assess CDK activity in algae. Although the results are easier to interpret in the context of synchronized cultures, the method is not limited to them. The protocol requires only standard laboratory equipment and access to a radioactivity working room. The method is applicable to any algal species, including newly developed ones, as it does not require any specific tools. The method can, therefore, be used to widen the portfolio of cell cycle regulatory models within algae.
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8
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Salomé PA, Merchant SS. Co-expression networks in Chlamydomonas reveal significant rhythmicity in batch cultures and empower gene function discovery. THE PLANT CELL 2021; 33:1058-1082. [PMID: 33793846 PMCID: PMC8226298 DOI: 10.1093/plcell/koab042] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 01/25/2021] [Indexed: 05/18/2023]
Abstract
The unicellular green alga Chlamydomonas reinhardtii is a choice reference system for the study of photosynthesis and chloroplast metabolism, cilium assembly and function, lipid and starch metabolism, and metal homeostasis. Despite decades of research, the functions of thousands of genes remain largely unknown, and new approaches are needed to categorically assign genes to cellular pathways. Growing collections of transcriptome and proteome data now allow a systematic approach based on integrative co-expression analysis. We used a dataset comprising 518 deep transcriptome samples derived from 58 independent experiments to identify potential co-expression relationships between genes. We visualized co-expression potential with the R package corrplot, to easily assess co-expression and anti-correlation between genes. We extracted several hundred high-confidence genes at the intersection of multiple curated lists involved in cilia, cell division, and photosynthesis, illustrating the power of our method. Surprisingly, Chlamydomonas experiments retained a significant rhythmic component across the transcriptome, suggesting an underappreciated variable during sample collection, even in samples collected in constant light. Our results therefore document substantial residual synchronization in batch cultures, contrary to assumptions of asynchrony. We provide step-by-step protocols for the analysis of co-expression across transcriptome data sets from Chlamydomonas and other species to help foster gene function discovery.
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9
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Ikui AE, Ueki N, Pecani K, Cross FR. Control of pre-replicative complex during the division cycle in Chlamydomonas reinhardtii. PLoS Genet 2021; 17:e1009471. [PMID: 33909603 PMCID: PMC8081180 DOI: 10.1371/journal.pgen.1009471] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 03/07/2021] [Indexed: 12/31/2022] Open
Abstract
DNA replication is fundamental to all living organisms. In yeast and animals, it is triggered by an assembly of pre-replicative complex including ORC, CDC6 and MCMs. Cyclin Dependent Kinase (CDK) regulates both assembly and firing of the pre-replicative complex. We tested temperature-sensitive mutants blocking Chlamydomonas DNA replication. The mutants were partially or completely defective in DNA replication and did not produce mitotic spindles. After a long G1, wild type Chlamydomonas cells enter a division phase when it undergoes multiple rapid synchronous divisions ('multiple fission'). Using tagged transgenic strains, we found that MCM4 and MCM6 were localized to the nucleus throughout the entire multiple fission division cycle, except for transient cytoplasmic localization during each mitosis. Chlamydomonas CDC6 was transiently localized in nucleus in early division cycles. CDC6 protein levels were very low, probably due to proteasomal degradation. CDC6 levels were severely reduced by inactivation of CDKA1 (CDK1 ortholog) but not the plant-specific CDKB1. Proteasome inhibition did not detectably increase CDC6 levels in the cdka1 mutant, suggesting that CDKA1 might upregulate CDC6 at the transcriptional level. All of the DNA replication proteins tested were essentially undetectable until late G1. They accumulated specifically during multiple fission and then were degraded as cells completed their terminal divisions. We speculate that loading of origins with the MCM helicase may not occur until the end of the long G1, unlike in the budding yeast system. We also developed a simple assay for salt-resistant chromatin binding of MCM4, and found that tight MCM4 loading was dependent on ORC1, CDC6 and MCM6, but not on RNR1 or CDKB1. These results provide a microbial framework for approaching replication control in the plant kingdom.
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Affiliation(s)
- Amy E. Ikui
- Department of Biology, Brooklyn College, The City University of New York, New York City, New York, United States of America
- * E-mail: (AEI); (FRC)
| | - Noriko Ueki
- Department of Biology, Brooklyn College, The City University of New York, New York City, New York, United States of America
| | - Kresti Pecani
- Laboratory of Cell Cycle Genetics, The Rockefeller University, New York City, New York, United States of America
| | - Frederick R. Cross
- Laboratory of Cell Cycle Genetics, The Rockefeller University, New York City, New York, United States of America
- * E-mail: (AEI); (FRC)
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10
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Lin YL, Chung CL, Huang PJ, Chen CH, Fang SC. Revised annotation and extended characterizations of components of the Chlamydomonas reinhardtii SUMOylation system. PLANT DIRECT 2020; 4:e00266. [PMID: 33015534 PMCID: PMC7522501 DOI: 10.1002/pld3.266] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 08/19/2020] [Accepted: 08/21/2020] [Indexed: 05/16/2023]
Abstract
Small ubiquitin-like modifier (SUMO) conjugation, or SUMOylation, is a reversible post-translational modification that is important for regulation of many cellular processes including cell division cycle in the eukaryotic kingdom. However, only a portion of the components of the Chlamydomonas SUMOylation system are known and their functions and regulation investigated. The present studies are aimed at extending discovery and characterization of new components and improving the annotation and nomenclature of all known proteins and genes involved in the system. Even though only one copy of the heterodimerized SUMO-activating enzyme, SAE1 and SAE2, was identified, the number of SUMO-conjugating enzymes (SCEs) and SUMO proteases/isopeptidase was expanded in Chlamydomonas. Using the reconstituted SUMOylation system, we showed that SCE1, SCE2, and SCE3 have SUMO-conjugating activity. In addition to SUMOylation, components required for other post-translational modifications such as NEDDylation, URMylation, and UFMylation, were confirmed to be present in Chlamydomonas. Our data also showed that besides isopeptidase activity, the SUMO protease domain of SUPPRESSOR OF MAT3 7/SENTRIN-SPECIFIC PROTEASE 1 (SMT7/SENP1) has endopeptidase activity that is capable of processing SUMO precursors. Moreover, the key cell cycle regulators of Chlamydomonas E2F1, DP1, CDKG1, CYCD2, and CYCD3 were SUMOylated in vitro, suggesting SUMOylation may be part of regulatory pathway modulating cell cycle regulators.
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Affiliation(s)
- Yen-Ling Lin
- Biotechnology Center in Southern Taiwan Academia Sinica Tainan Taiwan
- Agricultural Biotechnology Research Center Academia Sinica Taipei Taiwan
- Ph.D. Program in Microbial Genomics National Chung Hsing University and Academia Sinica Taichung Taiwan
| | - Chin-Lin Chung
- Biotechnology Center in Southern Taiwan Academia Sinica Tainan Taiwan
- Agricultural Biotechnology Research Center Academia Sinica Taipei Taiwan
| | - Pin-Jui Huang
- Biotechnology Center in Southern Taiwan Academia Sinica Tainan Taiwan
- Agricultural Biotechnology Research Center Academia Sinica Taipei Taiwan
| | - Chun-Han Chen
- Biotechnology Center in Southern Taiwan Academia Sinica Tainan Taiwan
- Agricultural Biotechnology Research Center Academia Sinica Taipei Taiwan
| | - Su-Chiung Fang
- Biotechnology Center in Southern Taiwan Academia Sinica Tainan Taiwan
- Agricultural Biotechnology Research Center Academia Sinica Taipei Taiwan
- Ph.D. Program in Microbial Genomics National Chung Hsing University and Academia Sinica Taichung Taiwan
- Institute of Tropical Plant Sciences and Microbiology National Cheng Kung University Tainan Taiwan
- National Cheng Kung University-Academia Sinica Graduate Program in Translational Agricultural Sciences Tainan Taiwan
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11
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Abstract
It is widely believed that cleavage-furrow formation during cytokinesis is driven by the contraction of a ring containing F-actin and type-II myosin. However, even in cells that have such rings, they are not always essential for furrow formation. Moreover, many taxonomically diverse eukaryotic cells divide by furrowing but have no type-II myosin, making it unlikely that an actomyosin ring drives furrowing. To explore this issue further, we have used one such organism, the green alga Chlamydomonas reinhardtii We found that although F-actin is associated with the furrow region, none of the three myosins (of types VIII and XI) is localized there. Moreover, when F-actin was eliminated through a combination of a mutation and a drug, furrows still formed and the cells divided, although somewhat less efficiently than normal. Unexpectedly, division of the large Chlamydomonas chloroplast was delayed in the cells lacking F-actin; as this organelle lies directly in the path of the cleavage furrow, this delay may explain, at least in part, the delay in cytokinesis itself. Earlier studies had shown an association of microtubules with the cleavage furrow, and we used a fluorescently tagged EB1 protein to show that microtubules are still associated with the furrows in the absence of F-actin, consistent with the possibility that the microtubules are important for furrow formation. We suggest that the actomyosin ring evolved as one way to improve the efficiency of a core process for furrow formation that was already present in ancestral eukaryotes.
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12
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Regulation of Multiple Fission and Cell-Cycle-Dependent Gene Expression by CDKA1 and the Rb-E2F Pathway in Chlamydomonas. Curr Biol 2020; 30:1855-1865.e4. [PMID: 32243861 DOI: 10.1016/j.cub.2020.03.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 02/06/2020] [Accepted: 03/09/2020] [Indexed: 01/07/2023]
Abstract
The green alga Chlamydomonas proliferates by "multiple fission": a long G1 with >10-fold cell growth followed by multiple rapid divisions. Cells above a critical size threshold are "committed" and will divide independent of light and further cell growth. The number of divisions carried out depends on the initial size of the committed mother cell. Here, I show that CDKA1, the ortholog of the yeast and animal mitotic inducer CDK1, regulates the critical size for commitment. The Rb/E2F/Dp1 pathway regulates division number as well as commitment size. Epistasis analysis indicated that CDKA1 and Rb/E2F/Dp1 regulate multiple fission by distinct mechanisms. Rb-E2F/Dp1 regulates G1/S gene expression in animals and land plants. Transcriptome analysis showed that mat3 or dp1 disruption altered regulation of a large group of cell-division-associated genes with respect to cell size, but not with respect to synchronization timing. In contrast, cdka1 inactivation disturbed both temporal and cell-size regulation of expression. These defects were enhanced by double inactivation of cdka1 and dp1, suggesting interaction between CDKA1 and the Rb-E2F/Dp1 pathways in regulating cell-cycle-specific gene expression and cell-cycle initiation. In the context of a theoretical model for regulation of Chlamydomonas multiple fission, these results suggest that CDKA1 may promote a switch into a division-competent state, and E2F/Dp1 may promote maintenance of this state.
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Lin YL, Chung CL, Chen MH, Chen CH, Fang SC. SUMO Protease SMT7 Modulates Ribosomal Protein L30 and Regulates Cell-Size Checkpoint Function. THE PLANT CELL 2020; 32:1285-1307. [PMID: 32060174 PMCID: PMC7145494 DOI: 10.1105/tpc.19.00301] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 01/02/2020] [Accepted: 02/11/2020] [Indexed: 05/10/2023]
Abstract
Proliferating cells actively coordinate growth and cell division to ensure cell-size homeostasis; however, the underlying mechanism through which size is controlled is poorly understood. Defect in a SUMO protease protein, suppressor of mat3 7 (SMT7), has been shown to reduce cell division number and increase cell size of the small-size mutant mating type locus 3-4 (mat3-4), which contains a defective retinoblastoma tumor suppressor-related protein of Chlamydomonas (Chlamydomonas reinhardtii). Here we describe development of an in vitro SUMOylation system using Chlamydomonas components and use it to provide evidence that SMT7 is a bona fide SUMO protease. We further demonstrate that the SUMO protease activity is required for supernumerous mitotic divisions of the mat3-4 cells. In addition, we identified RIBOSOMAL PROTEIN L30 (RPL30) as a prime SMT7 target and demonstrated that its SUMOylation is an important modulator of cell division in mat3-4 cells. Loss of SMT7 caused elevated SUMOylated RPL30 levels. Importantly, overexpression of the translational fusion version of RPL30-SUMO4, which mimics elevation of the SUMOylated RPL30 protein in mat3-4, caused a decrease in mitotic division and recapitulated the size-increasing phenotype of the smt7-1 mat3-4 cells. In summary, our study reveals a novel mechanism through which a SUMO protease regulates cell division in the mat3-4 mutant of Chlamydomonas and provides yet another important example of the role that protein SUMOylation can play in regulating key cellular processes, including cell division.
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Affiliation(s)
- Yen-Ling Lin
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
- Ph.D. Program in Microbial Genomics, National Chung Hsing University and Academia Sinica, Taichung 402, Taiwan
| | - Chin-Lin Chung
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Ming-Hui Chen
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Chun-Han Chen
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Su-Chiung Fang
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
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Heldt FS, Tyson JJ, Cross FR, Novák B. A Single Light-Responsive Sizer Can Control Multiple-Fission Cycles in Chlamydomonas. Curr Biol 2020; 30:634-644.e7. [DOI: 10.1016/j.cub.2019.12.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 09/25/2019] [Accepted: 12/09/2019] [Indexed: 12/18/2022]
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15
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Christensen JR, Craig EW, Glista MJ, Mueller DM, Li Y, Sees JA, Huang S, Suarez C, Mets LJ, Kovar DR, Avasthi P. Chlamydomonas reinhardtii formin FOR1 and profilin PRF1 are optimized for acute rapid actin filament assembly. Mol Biol Cell 2019; 30:3123-3135. [PMID: 31664873 PMCID: PMC6938247 DOI: 10.1091/mbc.e19-08-0463] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/10/2019] [Accepted: 10/24/2019] [Indexed: 12/18/2022] Open
Abstract
The regulated assembly of multiple filamentous actin (F-actin) networks from an actin monomer pool is important for a variety of cellular processes. Chlamydomonas reinhardtii is a unicellular green alga expressing a conventional and divergent actin that is an emerging system for investigating the complex regulation of actin polymerization. One actin network that contains exclusively conventional F-actin in Chlamydomonas is the fertilization tubule, a mating structure at the apical cell surface in gametes. In addition to two actin genes, Chlamydomonas expresses a profilin (PRF1) and four formin genes (FOR1-4), one of which (FOR1) we have characterized for the first time. We found that unlike typical profilins, PRF1 prevents unwanted actin assembly by strongly inhibiting both F-actin nucleation and barbed-end elongation at equimolar concentrations to actin. However, FOR1 stimulates the assembly of rapidly elongating actin filaments from PRF1-bound actin. Furthermore, for1 and prf1-1 mutants, as well as the small molecule formin inhibitor SMIFH2, prevent fertilization tubule formation in gametes, suggesting that polymerization of F-actin for fertilization tubule formation is a primary function of FOR1. Together, these findings indicate that FOR1 and PRF1 cooperate to selectively and rapidly assemble F-actin at the right time and place.
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Affiliation(s)
- Jenna R. Christensen
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - Evan W. Craig
- Department of Anatomy and Cell Biology , University of Kansas Medical Center, Kansas City, KS 66103
| | - Michael J. Glista
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - David M. Mueller
- Department of Anatomy and Cell Biology , University of Kansas Medical Center, Kansas City, KS 66103
| | - Yujie Li
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - Jennifer A. Sees
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - Shengping Huang
- Department of Ophthalmology, University of Kansas Medical Center, Kansas City, KS 66103
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - Laurens J. Mets
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - David R. Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
| | - Prachee Avasthi
- Department of Anatomy and Cell Biology , University of Kansas Medical Center, Kansas City, KS 66103
- Department of Ophthalmology, University of Kansas Medical Center, Kansas City, KS 66103
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Cell Cycle Arrest by Supraoptimal Temperature in the Alga Chlamydomonas reinhardtii. Cells 2019; 8:cells8101237. [PMID: 31614608 PMCID: PMC6829867 DOI: 10.3390/cells8101237] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/03/2019] [Accepted: 10/08/2019] [Indexed: 12/20/2022] Open
Abstract
Temperature is one of the key factors affecting growth and division of algal cells. High temperature inhibits the cell cycle in Chlamydomonas reinhardtii. At 39 °C, nuclear and cellular divisions in synchronized cultures were blocked completely, while DNA replication was partly affected. In contrast, growth (cell volume, dry matter, total protein, and RNA) remained unaffected, and starch accumulated at very high levels. The cell cycle arrest could be removed by transfer to 30 °C, but a full recovery occurred only in cultures cultivated up to 14 h at 39 °C. Thereafter, individual cell cycle processes began to be affected in sequence; daughter cell release, cell division, and DNA replication. Cell cycle arrest was accompanied by high mitotic cyclin-dependent kinase activity that decreased after completion of nuclear and cellular division following transfer to 30 °C. Cell cycle arrest was, therefore, not caused by a lack of cyclin-dependent kinase activity but rather a blockage in downstream processes.
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17
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Torres-Romero I, Kong F, Légeret B, Beisson F, Peltier G, Li-Beisson Y. Chlamydomonas cell cycle mutant crcdc5 over-accumulates starch and oil. Biochimie 2019; 169:54-61. [PMID: 31563539 DOI: 10.1016/j.biochi.2019.09.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Accepted: 09/23/2019] [Indexed: 10/25/2022]
Abstract
The use of algal biomass for biofuel production requires improvements in both biomass productivity and its energy density. Green microalgae store starch and oil as two major forms of carbon reserves. Current strategies to increase the amount of carbon reserves often compromise algal growth. To better understand the cellular mechanisms connecting cell division to carbon storage, we examined starch and oil accumulation in two Chlamydomonas mutants deficient in a gene encoding a homolog of the Arabidopsis Cell Division Cycle 5 (CDC5), a MYB DNA binding protein known to be involved in cell cycle in higher plants. The two crcdc5 mutants (crcdc5-1 and crcdc5-2) were found to accumulate significantly higher amount of starch and oil than their corresponding parental lines. Flow cytometry analysis on synchronized cultures cultivated in a diurnal light/dark cycle revealed an abnormal division of the two mutants, characterized by a prolonged S/M phase, therefore demonstrating its implication in cell cycle in Chlamydomonas. Taken together, these results suggest that the energy saved by a slowdown in cell division is used for the synthesis of reserve compounds. This work highlights the importance in understanding the interplay between cell cycle and starch/oil homeostasis, which should have a critical impact on improving lipid/starch productivity.
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Affiliation(s)
- Ismael Torres-Romero
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, 13108, Saint Paul-Lez-Durance, France
| | - Fantao Kong
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, 13108, Saint Paul-Lez-Durance, France
| | - Bertrand Légeret
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, 13108, Saint Paul-Lez-Durance, France
| | - Fred Beisson
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, 13108, Saint Paul-Lez-Durance, France
| | - Gilles Peltier
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, 13108, Saint Paul-Lez-Durance, France
| | - Yonghua Li-Beisson
- Aix Marseille Univ, CEA, CNRS, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, 13108, Saint Paul-Lez-Durance, France.
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Salomé PA, Merchant SS. A Series of Fortunate Events: Introducing Chlamydomonas as a Reference Organism. THE PLANT CELL 2019; 31:1682-1707. [PMID: 31189738 PMCID: PMC6713297 DOI: 10.1105/tpc.18.00952] [Citation(s) in RCA: 114] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 05/20/2019] [Accepted: 06/08/2019] [Indexed: 05/13/2023]
Abstract
The unicellular alga Chlamydomonas reinhardtii is a classical reference organism for studying photosynthesis, chloroplast biology, cell cycle control, and cilia structure and function. It is also an emerging model for studying sensory cilia, the production of high-value bioproducts, and in situ structural determination. Much of the early appeal of Chlamydomonas was rooted in its promise as a genetic system, but like other classic model organisms, this rise to prominence predated the discovery of the structure of DNA, whole-genome sequences, and molecular techniques for gene manipulation. The haploid genome of C. reinhardtii facilitates genetic analyses and offers many of the advantages of microbial systems applied to a photosynthetic organism. C. reinhardtii has contributed to our understanding of chloroplast-based photosynthesis and cilia biology. Despite pervasive transgene silencing, technological advances have allowed researchers to address outstanding lines of inquiry in algal research. The most thoroughly studied unicellular alga, C. reinhardtii, is the current standard for algal research, and although genome editing is still far from efficient and routine, it nevertheless serves as a template for other algae. We present a historical retrospective of the rise of C. reinhardtii to illuminate its past and present. We also present resources for current and future scientists who may wish to expand their studies to the realm of microalgae.
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Affiliation(s)
- Patrice A Salomé
- University of California, Los Angeles, Department of Chemistry and Biochemistry, Los Angeles, CA 90095
| | - Sabeeha S Merchant
- University of California, Los Angeles, Department of Chemistry and Biochemistry, Los Angeles, CA 90095
- University of California, Berkeley, Departments of Plant and Microbial Biology and Molecular and Cell Biology, Berkeley, CA 94720
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19
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Response of the Green Alga Chlamydomonas reinhardtii to the DNA Damaging Agent Zeocin. Cells 2019; 8:cells8070735. [PMID: 31319624 PMCID: PMC6678277 DOI: 10.3390/cells8070735] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 07/14/2019] [Accepted: 07/15/2019] [Indexed: 12/21/2022] Open
Abstract
DNA damage is a ubiquitous threat endangering DNA integrity in all living organisms. Responses to DNA damage include, among others, induction of DNA repair and blocking of cell cycle progression in order to prevent transmission of damaged DNA to daughter cells. Here, we tested the effect of the antibiotic zeocin, inducing double stranded DNA breaks, on the cell cycle of synchronized cultures of the green alga Chlamydomonas reinhardtii. After zeocin application, DNA replication partially occurred but nuclear and cellular divisions were completely blocked. Application of zeocin combined with caffeine, known to alleviate DNA checkpoints, decreased cell viability significantly. This was probably caused by a partial overcoming of the cell cycle progression block in such cells, leading to aberrant cell divisions. The cell cycle block was accompanied by high steady state levels of mitotic cyclin-dependent kinase activity. The data indicate that DNA damage response in C. reinhardtii is connected to the cell cycle block, accompanied by increased and stabilized mitotic cyclin-dependent kinase activity.
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20
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Abstract
Over 100 whole-genome sequences from algae are published or soon to be published. The rapidly increasing availability of these fundamental resources is changing how we understand one of the most diverse, complex, and understudied groups of photosynthetic eukaryotes. Genome sequences provide a window into the functional potential of individual algae, with phylogenomics and functional genomics as tools for contextualizing and transferring knowledge from reference organisms into less well-characterized systems. Remarkably, over half of the proteins encoded by algal genomes are of unknown function, highlighting the volume of functional capabilities yet to be discovered. In this review, we provide an overview of publicly available algal genomes, their associated protein inventories, and their quality, with a summary of the statuses of protein function understanding and predictions.
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Affiliation(s)
| | - Sabeeha S Merchant
- Departments of Plant and Microbial Biology and Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
- Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095, USA
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21
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Zachleder V, Ivanov I, Vítová M, Bišová K. Effects of cyclin-dependent kinase activity on the coordination of growth and the cell cycle in green algae at different temperatures. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:845-858. [PMID: 30395238 DOI: 10.1093/jxb/ery391] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 10/22/2018] [Indexed: 06/08/2023]
Abstract
The progression of the cell cycle in green algae dividing by multiple fission is, under otherwise unlimited conditions, affected by the growth rate, set by a combination of light intensity and temperature. In this study, we compared the cell cycle characteristics of Desmodesmus quadricauda at 20 °C or 30 °C and upon shifts between these two temperatures. The duration of the cell cycle in cells grown under continuous illumination at 20 °C was more than double that at 30 °C, suggesting that it was set directly by the growth rate. Similarly, the amounts of DNA, RNA, and bulk protein content per cell at 20 °C were approximately double those of cells grown at the higher temperature. For the shift experiments, cells grown at either 20 °C or 30 °C were transferred to darkness to prevent further growth, and then cultivated at the same or the other temperature. Upon transfer to the lower temperature, fewer nuclei and daughter cells were produced, and not all cells were able to finish the cell cycle by division, remaining multinuclear. Correspondingly, cells placed in the dark at the higher temperature divided faster into more daughter cells than the control cells. These differences correlated with shifts in the preceding cyclin-dependent kinase activity, suggesting that cell cycle progression was not related to growth rate or cell biomass but correlated with cyclin-dependent kinase activity.
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Affiliation(s)
- Vilém Zachleder
- Laboratory of Cell Cycles of Algae, Centre Algatech, Institute of Microbiology, Czech Academy of Sciences, Opatovický mlýn, Trebon, Czech Republic
| | - Ivan Ivanov
- Laboratory of Cell Cycles of Algae, Centre Algatech, Institute of Microbiology, Czech Academy of Sciences, Opatovický mlýn, Třeboň, Czech Republic
- Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, Czech Republic
| | - Milada Vítová
- Laboratory of Cell Cycles of Algae, Centre Algatech, Institute of Microbiology, Czech Academy of Sciences, Opatovický mlýn, Trebon, Czech Republic
| | - Katerina Bišová
- Laboratory of Cell Cycles of Algae, Centre Algatech, Institute of Microbiology, Czech Academy of Sciences, Opatovický mlýn, Trebon, Czech Republic
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22
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Multiomics resolution of molecular events during a day in the life of Chlamydomonas. Proc Natl Acad Sci U S A 2019; 116:2374-2383. [PMID: 30659148 PMCID: PMC6369806 DOI: 10.1073/pnas.1815238116] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The unicellular green alga Chlamydomonas reinhardtii displays metabolic flexibility in response to a changing environment. We analyzed expression patterns of its three genomes in cells grown under light-dark cycles. Nearly 85% of transcribed genes show differential expression, with different sets of transcripts being up-regulated over the course of the day to coordinate cellular growth before undergoing cell division. Parallel measurements of select metabolites and pigments, physiological parameters, and a subset of proteins allow us to infer metabolic events and to evaluate the impact of the transcriptome on the proteome. Among the findings are the observations that Chlamydomonas exhibits lower respiratory activity at night compared with the day; multiple fermentation pathways, some oxygen-sensitive, are expressed at night in aerated cultures; we propose that the ferredoxin, FDX9, is potentially the electron donor to hydrogenases. The light stress-responsive genes PSBS, LHCSR1, and LHCSR3 show an acute response to lights-on at dawn under abrupt dark-to-light transitions, while LHCSR3 genes also exhibit a later, second burst in expression in the middle of the day dependent on light intensity. Each response to light (acute and sustained) can be selectively activated under specific conditions. Our expression dataset, complemented with coexpression networks and metabolite profiling, should constitute an excellent resource for the algal and plant communities.
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Lin H, Cliften PF, Dutcher SK. MAPINS, a Highly Efficient Detection Method That Identifies Insertional Mutations and Complex DNA Rearrangements. PLANT PHYSIOLOGY 2018; 178:1436-1447. [PMID: 30206105 PMCID: PMC6288735 DOI: 10.1104/pp.18.00474] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 08/29/2018] [Indexed: 05/20/2023]
Abstract
Insertional mutagenesis, in which a piece of exogenous DNA is integrated randomly into the genomic DNA of the recipient cell, is a useful method to generate new mutants with phenotypes of interest. The unicellular green alga Chlamydomonas reinhardtii is an outstanding model for studying many biological processes. We developed a new computational algorithm, MAPINS (mapping insertions), to efficiently identify insertion sites created by the integration of an APHVIII (aminoglycoside 3'-phosphotransferase VIII) cassette that confers paromomycin resistance. Using whole-genome sequencing data, this method eliminates the need for genomic DNA manipulation and retains all the sequencing information provided by paired-end sequencing. We experimentally verified 38 insertion sites out of 41 sites (93%) identified by MAPINS from 20 paromomycin-resistant strains. Using meiotic analysis of 18 of these strains, we identified insertion sites that completely cosegregate with paromomycin resistance. In six of the seven strains with a mutant phenotype, we demonstrated complete cosegregation of the mutant phenotype and the verified insertion site. In addition, we provide direct evidence of complex rearrangements of genomic DNA in five strains, three of which involve the APHVIII insertion site. We suggest that strains obtained by insertional mutagenesis are more complicated than expected from previous analyses in Chlamydomonas To map the locations of some complex insertions, we designed 49 molecular markers based on differences identified via whole-genome sequencing between wild-type strains CC-124 and CC-125. Overall, MAPINS provides a low-cost, efficient method to characterize insertional mutants in Chlamydomonas.
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Affiliation(s)
- Huawen Lin
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Paul F Cliften
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Susan K Dutcher
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110
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Umen JG. Sizing up the cell cycle: systems and quantitative approaches in Chlamydomonas. CURRENT OPINION IN PLANT BIOLOGY 2018; 46:96-103. [PMID: 30212737 PMCID: PMC6269190 DOI: 10.1016/j.pbi.2018.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 08/14/2018] [Accepted: 08/16/2018] [Indexed: 05/06/2023]
Abstract
The unicellular green alga Chlamydomonas provides a simplified model for defining core cell cycle functions conserved in the green lineage and for understanding multiple fission, a common cell cycle variation found in many algae. Systems-level approaches including a recent groundbreaking screen for conditional lethal cell cycle mutants and genome-wide transcriptome analyses are revealing the complex relationships among cell cycle regulators and helping define roles for CDKA/CDK1 and CDKB, the latter of which is unique to the green lineage and plays a central role in mitotic regulation. Genetic screens and quantitative single-cell analyses have provided insight into cell-size control during multiple fission including the identification of a candidate `sizer' protein. Quantitative single-cell tracking and modeling are promising approaches for gaining additional insight into regulation of cellular and subcellular scaling during the Chlamydomonas cell cycle.
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Affiliation(s)
- James G Umen
- Donald Danforth Plant Science Center, 975 N. Warson Rd., St. Louis, MO 63132, USA.
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25
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F-actin homeostasis through transcriptional regulation and proteasome-mediated proteolysis. Proc Natl Acad Sci U S A 2018; 115:E6487-E6496. [PMID: 29941587 DOI: 10.1073/pnas.1721935115] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Many organisms possess multiple and often divergent actins whose regulation and roles are not understood in detail. For example, Chlamydomonas reinhardtii has both a conventional actin (IDA5) and a highly divergent one (NAP1); only IDA5 is expressed in normal proliferating cells. We showed previously that the drug latrunculin B (LatB) causes loss of filamentous (F-) IDA5 and strong up-regulation of NAP1, which then provides essential actin function(s) by forming LatB-resistant F-NAP1. RNA-sequencing analyses now show that this up-regulation of NAP1 reflects a broad transcriptional response, much of which depends on three proteins (LAT1, LAT2, and LAT3) identified previously as essential for NAP1 transcription. Many of the LAT-regulated genes contain a putative cis-acting regulatory site, the "LRE motif." The LatB transcriptional program appears to be activated by loss of F-IDA5 and deactivated by formation of F-NAP1, thus forming an F-actin-dependent negative-feedback loop. Multiple genes encoding proteins of the ubiquitin-proteasome system are among those induced by LatB, resulting in rapid degradation of IDA5 (but not NAP1). Our results suggest that IDA5 degradation is functionally important because nonpolymerizable LatB-bound IDA5 interferes with the formation of F-NAP1. The genes for the actin-interacting proteins cofilin and profilin are also induced. Cofilin induction may further the clearance of IDA5 by promoting the scission of F-IDA5, whereas profilin appears to function in protecting monomeric IDA5 from degradation. This multifaceted regulatory system allows rapid and quantitative turnover of F-actin in response to cytoskeletal perturbations and probably also maintains F-actin homeostasis under normal growth conditions.
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26
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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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Atkins KC, Cross FR. Interregulation of CDKA/CDK1 and the Plant-Specific Cyclin-Dependent Kinase CDKB in Control of the Chlamydomonas Cell Cycle. THE PLANT CELL 2018; 30:429-446. [PMID: 29367304 PMCID: PMC5868683 DOI: 10.1105/tpc.17.00759] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 11/17/2017] [Accepted: 01/24/2018] [Indexed: 05/09/2023]
Abstract
The cyclin-dependent kinase CDK1 is essential for mitosis in fungi and animals. Plant genomes contain the CDK1 ortholog CDKA and a plant kingdom-specific relative, CDKB. The green alga Chlamydomonas reinhardtii has a long G1 growth period followed by rapid cycles of DNA replication and cell division. We show that null alleles of CDKA extend the growth period prior to the first division cycle and modestly extend the subsequent division cycles, but do not prevent cell division, indicating at most a minor role for the CDK1 ortholog in mitosis in Chlamydomonas. A null allele of cyclin A has a similar though less extreme phenotype. In contrast, both CDKB and cyclin B are essential for mitosis. CDK kinase activity measurements imply that the predominant in vivo complexes are probably cyclin A-CDKA and cyclin B-CDKB. We propose a negative feedback loop: CDKA activates cyclin B-CDKB. Cyclin B-CDKB in turn promotes mitotic entry and inactivates cyclin A-CDKA. Cyclin A-CDKA and cyclin B-CDKB may redundantly promote DNA replication. We show that the anaphase-promoting complex is required for inactivation of both CDKA and CDKB and is essential for anaphase. These results are consistent with findings in Arabidopsis thaliana and may delineate the core of plant kingdom cell cycle control that, compared with the well-studied yeast and animal systems, exhibits deep conservation in some respects and striking divergence in others.
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Komaki S, Schnittger A. The Spindle Assembly Checkpoint in Arabidopsis Is Rapidly Shut Off during Severe Stress. Dev Cell 2017; 43:172-185.e5. [PMID: 29065308 DOI: 10.1016/j.devcel.2017.09.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 07/18/2017] [Accepted: 09/21/2017] [Indexed: 12/24/2022]
Abstract
The spindle assembly checkpoint (SAC) in animals and yeast assures equal segregation of chromosomes during cell division. The prevalent occurrence of polyploidy in flowering plants together with the observation that many plants can be readily forced to double their genomes by application of microtubule drugs raises the question of whether plants have a proper SAC. Here, we provide a functional framework of the core SAC proteins in Arabidopsis. We reveal that Arabidopsis will delay mitosis in a SAC-dependent manner if the spindle is perturbed. However, we also show that the molecular architecture of the SAC is unique in plants. Moreover, the SAC is short-lived and cannot stay active for more than 2 hr, after which the cell cycle is reset. This resetting opens the possibility for genome duplications and raises the hypothesis that a rapid termination of a SAC-induced mitotic arrest provides an adaptive advantage for plants impacting plant genome evolution.
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Affiliation(s)
- Shinichiro Komaki
- University of Hamburg, Biozentrum Klein Flottbek, Department of Developmental Biology, Ohnhorststrasse 18, D-22609 Hamburg, Germany
| | - Arp Schnittger
- University of Hamburg, Biozentrum Klein Flottbek, Department of Developmental Biology, Ohnhorststrasse 18, D-22609 Hamburg, Germany.
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29
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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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Shelton DE, Leslie MP, Michod RE. Models of cell division initiation in Chlamydomonas: A challenge to the consensus view. J Theor Biol 2017; 412:186-197. [PMID: 27816674 DOI: 10.1016/j.jtbi.2016.10.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 09/19/2016] [Accepted: 10/25/2016] [Indexed: 11/28/2022]
Abstract
We develop and compare two models for division initiation in cells of the unicellular green alga Chlamydomonas reinhardtii, a topic that has remained controversial in spite of years of empirical work. Achieving a better understanding of C. reinhardtii cell cycle regulation is important because this species is used in studies of fundamental eukaryotic cell features and in studies of the evolution of multicellularity. C. reinhardtii proliferates asexually by multiple fission, interspersing rapid rounds of symmetric division with prolonged periods of growth. Our Model 1 reflects major elements of the current consensus view on C. reinhardtii division initiation, with cells first growing to a specific size, then waiting for a particular time prior to division initiation. In Model 2, our proposed alternative, growing cells divide when they have reached a growth-rate-dependent target size. The two models imply a number of different empirical patterns. We highlight these differences alongside published data, which currently fall short of unequivocally distinguishing these differences in predicted cell behavior. Nevertheless, several lines of evidence are suggestive of more Model 2-like behavior than Model 1-like behavior. Our specification of these models adds rigor to issues that have too often been worked out in relation to loose, verbal models and is directly relevant to future development of informative experiments.
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Affiliation(s)
- Deborah E Shelton
- Department of Ecology and Evolutionary Biology, University of Arizona, 1041 E. Lowell St. Tucson, AZ 85721, United States.
| | - Martin P Leslie
- Department of Ecology and Evolutionary Biology, University of Arizona, 1041 E. Lowell St. Tucson, AZ 85721, United States
| | - Richard E Michod
- Department of Ecology and Evolutionary Biology, University of Arizona, 1041 E. Lowell St. Tucson, AZ 85721, United States; Kavli Institute for Theoretical Physics, University of California Santa Barbara, Santa Barbara, CA 93106, United States
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31
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Pokora W, Aksmann A, Baścik-Remisiewicz A, Dettlaff-Pokora A, Rykaczewski M, Gappa M, Tukaj Z. Changes in nitric oxide/hydrogen peroxide content and cell cycle progression: Study with synchronized cultures of green alga Chlamydomonas reinhardtii. JOURNAL OF PLANT PHYSIOLOGY 2017; 208:84-93. [PMID: 27894022 DOI: 10.1016/j.jplph.2016.10.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 10/07/2016] [Accepted: 10/09/2016] [Indexed: 05/06/2023]
Abstract
The present study aimed to evaluate the possible relationship between the changes in hydrogen peroxide (H2O2) and nitric oxide (NO) content and the course of growth and reproductive processes of the cell cycle of Chlamydomonas reinhardtii. The peak of H2O2 observed at the beginning of the cell cycle was found to originate from Fe-SOD and Mn-SODchl. activity and result from the alternation in the photosynthetic processes caused by the dark-to-light transition of daughter cells. A rapid increase in NO concentration, observed before the light-to-dark cell transition, originated from NR and NIR activity and was followed by a photosynthesis-independent, Mn-SODchl.-mediated increases in H2O2 production. This H2O2 peak overlapped the beginning of Chlamydomonas cell division, which was indicated by a profile of CYCs and CDKs characteristic of cells' passage through the G1/S and S/M checkpoints. Taken together, our results show that there is a clear relationship between the course of the Chlamydomonas cell cycle and typical changes in the H2O2/NO ratio, as well as changes in expression and activity of enzymes involved in generation and scavenging of these signaling molecules.
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Affiliation(s)
- Wojciech Pokora
- Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland.
| | - Anna Aksmann
- Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Agnieszka Baścik-Remisiewicz
- Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland
| | | | - Max Rykaczewski
- Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Magdalena Gappa
- Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Zbigniew Tukaj
- Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland
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32
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Breker M, Lieberman K, Tulin F, Cross FR. High-Throughput Robotically Assisted Isolation of Temperature-sensitive Lethal Mutants in Chlamydomonas reinhardtii. J Vis Exp 2016. [PMID: 28060315 PMCID: PMC5226362 DOI: 10.3791/54831] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Systematic identification and characterization of genetic perturbations have proven useful to decipher gene function and cellular pathways. However, the conventional approaches of permanent gene deletion cannot be applied to essential genes. We have pioneered a unique collection of ~70 temperature-sensitive (ts) lethal mutants for studying cell cycle regulation in the unicellular green algae Chlamydomonas reinhardtii1. These mutations identify essential genes, and the ts alleles can be conditionally inactivated by temperature shift, providing valuable tools to identify and analyze essential functions. Mutant collections are much more valuable if they are close to comprehensive, since scattershot collections can miss important components. However, this requires the efficient collection of a large number of mutants, especially in a wide-target screen. Here, we describe a robotics-based pipeline for generating ts lethal mutants and analyzing their phenotype in Chlamydomonas. This technique can be applied to any microorganism that grows on agar. We have collected over 3000 ts mutants, probably including mutations in most or all cell-essential pathways, including about 200 new candidate cell cycle mutations. Subsequent molecular and cellular characterization of these mutants should provide new insights in plant cell biology; a comprehensive mutant collection is an essential prerequisite to ensure coverage of a broad range of biological pathways. These methods are integrated with downstream genetics and bioinformatics procedures for efficient mapping and identification of the causative mutations that are beyond the scope of this manuscript.
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Affiliation(s)
- Michal Breker
- Laboratory of Cell Cycle Genetics, The Rockefeller University
| | | | - Frej Tulin
- Sainsbury Laboratory, University of Cambridge
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Morse D, Daoust P, Benribague S. A Transcriptome-based Perspective of Cell Cycle Regulation in Dinoflagellates. Protist 2016; 167:610-621. [PMID: 27816812 DOI: 10.1016/j.protis.2016.10.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 09/29/2016] [Accepted: 10/08/2016] [Indexed: 11/25/2022]
Abstract
Dinoflagellates are a group of unicellular and generally marine protists, of interest to many because of their ability to form the large algal blooms commonly called "red tides". The large algal concentrations in these blooms require sustained cell replication, yet to date little is known about cell cycle regulation in these organisms. To address this issue, we have screened the transcriptomes of two dinoflagellates, Lingulodinium polyedrum and Symbiodinium sp., with budding yeast cell cycle pathway components. We find most yeast cell cycle regulators have homologs in these dinoflagellates, suggesting that the yeast model is appropriate for understanding regulation of the dinoflagellate cell cycle. The dinoflagellates are lacking several components essential in yeast, but a comparison with a broader phylogenetic range of protists reveals these components are usually also missing in other organisms. Lastly, phylogenetic analyses show that the dinoflagellates contain at least three cyclin-dependent kinase (CDK) homologs (belonging to the CDK1, CDK5 and CDK8 families), and that the dinoflagellate cyclins belong exclusively to the A/B type. This suggests that dinoflagellate CDKs likely play a limited role outside regulation of the cell cycle.
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Affiliation(s)
- David Morse
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, Montréal, Québec, Canada H1X 2B2.
| | - Philip Daoust
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, Montréal, Québec, Canada H1X 2B2
| | - Siham Benribague
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, Montréal, Québec, Canada H1X 2B2
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Weimer AK, Biedermann S, Harashima H, Roodbarkelari F, Takahashi N, Foreman J, Guan Y, Pochon G, Heese M, Van Damme D, Sugimoto K, Koncz C, Doerner P, Umeda M, Schnittger A. The plant-specific CDKB1-CYCB1 complex mediates homologous recombination repair in Arabidopsis. EMBO J 2016; 35:2068-2086. [PMID: 27497297 PMCID: PMC5048351 DOI: 10.15252/embj.201593083] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 07/14/2016] [Indexed: 01/30/2023] Open
Abstract
Upon DNA damage, cyclin‐dependent kinases (CDKs) are typically inhibited to block cell division. In many organisms, however, it has been found that CDK activity is required for DNA repair, especially for homology‐dependent repair (HR), resulting in the conundrum how mitotic arrest and repair can be reconciled. Here, we show that Arabidopsis thaliana solves this dilemma by a division of labor strategy. We identify the plant‐specific B1‐type CDKs (CDKB1s) and the class of B1‐type cyclins (CYCB1s) as major regulators of HR in plants. We find that RADIATION SENSITIVE 51 (RAD51), a core mediator of HR, is a substrate of CDKB1‐CYCB1 complexes. Conversely, mutants in CDKB1 and CYCB1 fail to recruit RAD51 to damaged DNA. CYCB1;1 is specifically activated after DNA damage and we show that this activation is directly controlled by SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1), a transcription factor that acts similarly to p53 in animals. Thus, while the major mitotic cell‐cycle activity is blocked after DNA damage, CDKB1‐CYCB1 complexes are specifically activated to mediate HR.
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Affiliation(s)
- Annika K Weimer
- Department of Molecular Mechanisms of Phenotypic Plasticity, Institut de Biologie Moléculaire des Plantes du CNRS, IBMP-CNRS UPR2357, Université de Strasbourg, Strasbourg Cedex, France
| | - Sascha Biedermann
- Department of Molecular Mechanisms of Phenotypic Plasticity, Institut de Biologie Moléculaire des Plantes du CNRS, IBMP-CNRS UPR2357, Université de Strasbourg, Strasbourg Cedex, France
| | | | | | - Naoki Takahashi
- Plant Growth Regulation Laboratory, Nara Institute of Science and Technology, Graduate School of Biological Sciences, Ikoma, Nara, Japan
| | - Julia Foreman
- School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Yonsheng Guan
- Department of Molecular Mechanisms of Phenotypic Plasticity, Institut de Biologie Moléculaire des Plantes du CNRS, IBMP-CNRS UPR2357, Université de Strasbourg, Strasbourg Cedex, France
| | - Gaëtan Pochon
- Department of Developmental Biology, Biozentrum Klein Flottbek, University of Hamburg, Hamburg, Germany
| | - Maren Heese
- Department of Developmental Biology, Biozentrum Klein Flottbek, University of Hamburg, Hamburg, Germany
| | - Daniël Van Damme
- Department of Plant Systems Biology, VIB, Ghent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
| | - Keiko Sugimoto
- RIKEN Center for Sustainable Resource Science, Tsurumi, Yokohama, Japan
| | - Csaba Koncz
- Max-Planck-Institut für Pflanzenzüchtungsforschung, Köln, Germany
| | - Peter Doerner
- School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Masaaki Umeda
- Plant Growth Regulation Laboratory, Nara Institute of Science and Technology, Graduate School of Biological Sciences, Ikoma, Nara, Japan JST, CREST, Ikoma, Nara, Japan
| | - Arp Schnittger
- Department of Molecular Mechanisms of Phenotypic Plasticity, Institut de Biologie Moléculaire des Plantes du CNRS, IBMP-CNRS UPR2357, Université de Strasbourg, Strasbourg Cedex, France Department of Developmental Biology, Biozentrum Klein Flottbek, University of Hamburg, Hamburg, Germany Trinationales Institut für Pflanzenforschung, Institut de Biologie Moléculaire des Plantes du CNRS, IBMP-CNRS, Strasbourg Cedex, France
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35
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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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36
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Hong S, Song M, Kim S, Bang D, Kang T, Choi I, Lee LP. Integrated Microalgae Analysis Photobioreactor for Rapid Strain Selection. ACS NANO 2016; 10:5635-5642. [PMID: 27227421 DOI: 10.1021/acsnano.6b00803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Algal photosynthesis is considered to be a sustainable, alternative, and renewable solution to generating green energy. For high-productivity algaculture in diverse local environments, a high-throughput screening method is needed to select algal strains from naturally available or genetically engineered strains. Herein, we present an integrated plasmonic photobioreactor for rapid, high-throughput screening of microalgae. Our 3D nanoplasmonic optical cavity-based photobioreactor permits the amplification of a selective wavelength favorable to photosynthesis in the cavity. The hemispheric plasmonic cavity allows intercellular interaction to be promoted in the optically favorable milieu and also permits effective visual examination of algal growth. Using Chlamydomonas reinhardtii, we demonstrated a 2-fold enhanced growth rate and a 1.5-fold lipid production rate with no distinctive lag phase. By facilitating growth and biomass conversion rates, the integrated microalgae analysis platform will serve as rapid microalgae screening platforms for biofuel applications.
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Affiliation(s)
| | | | | | | | - Taewook Kang
- Department of Chemical and Biomolecular Engineering, Sogang University , Seoul 121-742, Korea
| | - Inhee Choi
- Department of Life Science, University of Seoul , Seoul 130-743, Korea
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Li Y, Liu D, López-Paz C, Olson BJ, Umen JG. A new class of cyclin dependent kinase in Chlamydomonas is required for coupling cell size to cell division. eLife 2016; 5:e10767. [PMID: 27015111 PMCID: PMC4841777 DOI: 10.7554/elife.10767] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 03/24/2016] [Indexed: 01/04/2023] Open
Abstract
Proliferating cells actively control their size by mechanisms that are poorly understood. The unicellular green alga Chlamydomonas reinhardtii divides by multiple fission, wherein a ‘counting’ mechanism couples mother cell-size to cell division number allowing production of uniform-sized daughters. We identified a sizer protein, CDKG1, that acts through the retinoblastoma (RB) tumor suppressor pathway as a D-cyclin-dependent RB kinase to regulate mitotic counting. Loss of CDKG1 leads to fewer mitotic divisions and large daughters, while mis-expression of CDKG1 causes supernumerous mitotic divisions and small daughters. The concentration of nuclear-localized CDKG1 in pre-mitotic cells is set by mother cell size, and its progressive dilution and degradation with each round of cell division may provide a link between mother cell-size and mitotic division number. Cell-size-dependent accumulation of limiting cell cycle regulators such as CDKG1 is a potentially general mechanism for size control. DOI:http://dx.doi.org/10.7554/eLife.10767.001 Most cells are programmed to maintain a certain size. This property, known as size control, is achieved by balancing growth and division, such that a cell will only divide after it reaches a certain size. However, and despite years of research, it is largely unknown how cells sense their size (or growth) to be able to divide accordingly. One theory proposes that there is a “sizer” protein inside cells, and that cells measure the abundance of this protein and use it to link cell size to the process of division. However, the existence of such a protein remained unproven. Li, Liu et al. have now used the cells of the green alga Chlamydomonas to identify a candidate sizer protein. Chlamydomonas cells, like many other algae, can grow to become very large mother cells that then divide one or more times in succession to produce many daughter cells. Larger mother cells undergo more divisions than smaller mother cells in order to produce daughter cells of a correct size. Using a range of genetic and biochemical techniques, Li, Liu et al. identified a protein that is produced in Chlamydomonas cells just before they begin to divide. Larger mother cells contain more of this protein than smaller cells and the protein encourages cells to divide. For example, mutant cells that lack this protein divided too few times, while cells that produce too much of it divided too many times. The protein, called CDKG1, belongs to a family of proteins that regulate cell division in many organisms. CDKG1 is a kinase – an enzyme that alters the activity of other proteins by adding a phosphate group on to them. In Chlamydomonas, CDKG1 couples cell size to cell division by altering the activity of an important protein called the retinoblastoma-related protein that controls cell division in numerous organisms. This protein is also frequently disrupted in cancers in humans. These findings shed new light on a molecular pathway for size control. Future work will need to determine how the accumulation of CDKG1 links to the size of a mother cell and how it is inactivated once daughter cells reach the appropriate size. DOI:http://dx.doi.org/10.7554/eLife.10767.002
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Affiliation(s)
- Yubing Li
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States.,Plant Molecular and Cell Biology Program, the Horticultural and Plant Science Department, University of Florida, Gainesville, United States
| | - Dianyi Liu
- Donald Danforth Plant Science Center, St. Louis, United States
| | - Cristina López-Paz
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States.,Donald Danforth Plant Science Center, St. Louis, United States
| | - Bradley Jsc Olson
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States
| | - James G Umen
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States.,Donald Danforth Plant Science Center, St. Louis, United States
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38
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Li X, Zhang R, Patena W, Gang SS, Blum SR, Ivanova N, Yue R, Robertson JM, Lefebvre PA, Fitz-Gibbon ST, Grossman AR, Jonikas MC. An Indexed, Mapped Mutant Library Enables Reverse Genetics Studies of Biological Processes in Chlamydomonas reinhardtii. THE PLANT CELL 2016; 28:367-87. [PMID: 26764374 PMCID: PMC4790863 DOI: 10.1105/tpc.15.00465] [Citation(s) in RCA: 231] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 11/30/2015] [Accepted: 01/11/2016] [Indexed: 05/18/2023]
Abstract
The green alga Chlamydomonas reinhardtii is a leading unicellular model for dissecting biological processes in photosynthetic eukaryotes. However, its usefulness has been limited by difficulties in obtaining mutants in specific genes of interest. To allow generation of large numbers of mapped mutants, we developed high-throughput methods that (1) enable easy maintenance of tens of thousands of Chlamydomonas strains by propagation on agar media and by cryogenic storage, (2) identify mutagenic insertion sites and physical coordinates in these collections, and (3) validate the insertion sites in pools of mutants by obtaining >500 bp of flanking genomic sequences. We used these approaches to construct a stably maintained library of 1935 mapped mutants, representing disruptions in 1562 genes. We further characterized randomly selected mutants and found that 33 out of 44 insertion sites (75%) could be confirmed by PCR, and 17 out of 23 mutants (74%) contained a single insertion. To demonstrate the power of this library for elucidating biological processes, we analyzed the lipid content of mutants disrupted in genes encoding proteins of the algal lipid droplet proteome. This study revealed a central role of the long-chain acyl-CoA synthetase LCS2 in the production of triacylglycerol from de novo-synthesized fatty acids.
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Affiliation(s)
- Xiaobo Li
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Ru Zhang
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Weronika Patena
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Spencer S Gang
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Sean R Blum
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Nina Ivanova
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Rebecca Yue
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Jacob M Robertson
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Paul A Lefebvre
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108
| | - Sorel T Fitz-Gibbon
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095
| | - Arthur R Grossman
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Martin C Jonikas
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
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39
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40
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Li X, Jonikas MC. High-Throughput Genetics Strategies for Identifying New Components of Lipid Metabolism in the Green Alga Chlamydomonas reinhardtii. Subcell Biochem 2016; 86:223-247. [PMID: 27023238 DOI: 10.1007/978-3-319-25979-6_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Microalgal lipid metabolism is of broad interest because microalgae accumulate large amounts of triacylglycerols (TAGs) that can be used for biodiesel production (Durrett et al Plant J 54(4):593-607, 2008; Hu et al Plant J 54(4):621-639, 2008). Additionally, green algae are close relatives of land plants and serve as models to understand conserved lipid metabolism pathways in the green lineage. The green alga Chlamydomonas reinhardtii (Chlamydomonas hereafter) is a powerful model organism for understanding algal lipid metabolism. Various methods have been used to screen Chlamydomonas mutants for lipid amount or composition, and for identification of the mutated loci in mutants of interest. In this chapter, we summarize the advantages and caveats for each of these methods with a focus on screens for mutants with perturbed TAG content. We also discuss technical opportunities and new tools that are becoming available for screens of mutants altered in TAG content or perturbed in other processes in Chlamydomonas.
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Affiliation(s)
- Xiaobo Li
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
| | - Martin C Jonikas
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA.
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Evidence That an Unconventional Actin Can Provide Essential F-Actin Function and That a Surveillance System Monitors F-Actin Integrity in Chlamydomonas. Genetics 2015; 202:977-96. [PMID: 26715672 DOI: 10.1534/genetics.115.184663] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 12/28/2015] [Indexed: 12/21/2022] Open
Abstract
Actin is one of the most conserved eukaryotic proteins. It is thought to have multiple essential cellular roles and to function primarily or exclusively as filaments ("F-actin"). Chlamydomonas has been an enigma, because a null mutation (ida5-1) in its single gene for conventional actin does not affect growth. A highly divergent actin gene, NAP1, is upregulated in ida5-1 cells, but it has been unclear whether NAP1 can form filaments or provide actin function. Here, we used the actin-depolymerizing drug latrunculin B (LatB), the F-actin-specific probe Lifeact-Venus, and genetic and molecular methods to resolve these issues. LatB-treated wild-type cells continue to proliferate; they initially lose Lifeact-stained structures but recover them concomitant with upregulation of NAP1. Thirty-nine LatB-sensitive mutants fell into four genes (NAP1 and LAT1-LAT3) in which we identified the causative mutations using a novel combinatorial pool-sequencing strategy. LAT1-LAT3 are required for NAP1 upregulation upon LatB treatment, and ectopic expression of NAP1 largely rescues the LatB sensitivity of the lat1-lat3 mutants, suggesting that the LAT gene products comprise a regulatory hierarchy with NAP1 expression as the major functional output. Selection of LatB-resistant revertants of a nap1 mutant yielded dominant IDA5 mutations that presumably render F-IDA5 resistant to LatB, and nap1 and lat mutations are synthetically lethal with ida5-1 in the absence of LatB. We conclude that both IDA5 and the divergent NAP1 can form filaments and redundantly provide essential F-actin functions and that a novel surveillance system, probably responding to a loss of F-actin, triggers NAP1 expression and perhaps other compensatory responses.
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Zones JM, Blaby IK, Merchant SS, Umen JG. High-Resolution Profiling of a Synchronized Diurnal Transcriptome from Chlamydomonas reinhardtii Reveals Continuous Cell and Metabolic Differentiation. THE PLANT CELL 2015; 27:2743-69. [PMID: 26432862 PMCID: PMC4682324 DOI: 10.1105/tpc.15.00498] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/27/2015] [Accepted: 09/14/2015] [Indexed: 05/18/2023]
Abstract
The green alga Chlamydomonas reinhardtii is a useful model organism for investigating diverse biological processes, such as photosynthesis and chloroplast biogenesis, flagella and basal body structure/function, cell growth and division, and many others. We combined a highly synchronous photobioreactor culture system with frequent temporal sampling to characterize genome-wide diurnal gene expression in Chlamydomonas. Over 80% of the measured transcriptome was expressed with strong periodicity, forming 18 major clusters. Genes associated with complex structures and processes, including cell cycle control, flagella and basal bodies, ribosome biogenesis, and energy metabolism, all had distinct signatures of coexpression with strong predictive value for assigning and temporally ordering function. Importantly, the frequent sampling regime allowed us to discern meaningful fine-scale phase differences between and within subgroups of genes and enabled the identification of a transiently expressed cluster of light stress genes. Coexpression was further used both as a data-mining tool to classify and/or validate genes from other data sets related to the cell cycle and to flagella and basal bodies and to assign isoforms of duplicated enzymes to their cognate pathways of central carbon metabolism. Our diurnal coexpression data capture functional relationships established by dozens of prior studies and are a valuable new resource for investigating a variety of biological processes in Chlamydomonas and other eukaryotes.
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Affiliation(s)
- James Matt Zones
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132 Division of Biological Sciences, University of California San Diego, La Jolla, California 92093
| | - Ian K Blaby
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095
| | - Sabeeha S Merchant
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095 Institute of Genomics and Proteomics, University of California, Los Angeles, California 90095
| | - James G Umen
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132
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Tulin F, Cross FR. Cyclin-Dependent Kinase Regulation of Diurnal Transcription in Chlamydomonas. THE PLANT CELL 2015; 27:2727-42. [PMID: 26475866 PMCID: PMC4682320 DOI: 10.1105/tpc.15.00400] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/01/2015] [Accepted: 09/18/2015] [Indexed: 05/18/2023]
Abstract
We analyzed global transcriptome changes during synchronized cell division in the green alga Chlamydomonas reinhardtii. The Chlamydomonas cell cycle consists of a long G1 phase, followed by an S/M phase with multiple rapid, alternating rounds of DNA replication and segregation. We found that the S/M period is associated with strong induction of ∼2300 genes, many with conserved roles in DNA replication or cell division. Other genes, including many involved in photosynthesis, are reciprocally downregulated in S/M, suggesting a gene expression split correlating with the temporal separation between G1 and S/M. The Chlamydomonas cell cycle is synchronized by light-dark cycles, so in principle, these transcriptional changes could be directly responsive to light or to metabolic cues. Alternatively, cell-cycle-periodic transcription may be directly regulated by cyclin-dependent kinases. To distinguish between these possibilities, we analyzed transcriptional profiles of mutants in the kinases CDKA and CDKB, as well as other mutants with distinct cell cycle blocks. Initial cell-cycle-periodic expression changes are largely CDK independent, but later regulation (induction and repression) is under differential control by CDKA and CDKB. Deviation from the wild-type transcriptional program in diverse cell cycle mutants will be an informative phenotype for further characterization of the Chlamydomonas cell cycle.
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Affiliation(s)
- Frej Tulin
- The Rockefeller University, New York, NY
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Jinkerson RE, Jonikas MC. Molecular techniques to interrogate and edit the Chlamydomonas nuclear genome. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 82:393-412. [PMID: 25704665 DOI: 10.1111/tpj.12801] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/13/2015] [Accepted: 02/16/2015] [Indexed: 05/23/2023]
Abstract
The success of the green alga Chlamydomonas reinhardtii as a model organism is to a large extent due to the wide range of molecular techniques that are available for its characterization. Here, we review some of the techniques currently used to modify and interrogate the C. reinhardtii nuclear genome and explore several technologies under development. Nuclear mutants can be generated with ultraviolet (UV) light and chemical mutagens, or by insertional mutagenesis. Nuclear transformation methods include biolistic delivery, agitation with glass beads, and electroporation. Transforming DNA integrates into the genome at random sites, and multiple strategies exist for mapping insertion sites. A limited number of studies have demonstrated targeted modification of the nuclear genome by approaches such as zinc-finger nucleases and homologous recombination. RNA interference is widely used to knock down expression levels of nuclear genes. A wide assortment of transgenes has been successfully expressed in the Chlamydomonas nuclear genome, including transformation markers, fluorescent proteins, reporter genes, epitope tagged proteins, and even therapeutic proteins. Optimized expression constructs and strains help transgene expression. Emerging technologies such as the CRISPR/Cas9 system, high-throughput mutant identification, and a whole-genome knockout library are being developed for this organism. We discuss how these advances will propel future investigations.
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Affiliation(s)
- Robert E Jinkerson
- Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA, 94305, USA
| | - Martin C Jonikas
- Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA, 94305, USA
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Cross FR, Umen JG. The Chlamydomonas cell cycle. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 82:370-392. [PMID: 25690512 PMCID: PMC4409525 DOI: 10.1111/tpj.12795] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/03/2015] [Accepted: 02/04/2015] [Indexed: 05/18/2023]
Abstract
The position of Chlamydomonas within the eukaryotic phylogeny makes it a unique model in at least two important ways: as a representative of the critically important, early-diverging lineage leading to plants; and as a microbe retaining important features of the last eukaryotic common ancestor (LECA) that has been lost in the highly studied yeast lineages. Its cell biology has been studied for many decades and it has well-developed experimental genetic tools, both classical (Mendelian) and molecular. Unlike land plants, it is a haploid with very few gene duplicates, making it ideal for loss-of-function genetic studies. The Chlamydomonas cell cycle has a striking temporal and functional separation between cell growth and rapid cell division, probably connected to the interplay between diurnal cycles that drive photosynthetic cell growth and the cell division cycle; it also exhibits a highly choreographed interaction between the cell cycle and its centriole-basal body-flagellar cycle. Here, we review the current status of studies of the Chlamydomonas cell cycle. We begin with an overview of cell-cycle control in the well-studied yeast and animal systems, which has yielded a canonical, well-supported model. We discuss briefly what is known about similarities and differences in plant cell-cycle control, compared with this model. We next review the cytology and cell biology of the multiple-fission cell cycle of Chlamydomonas. Lastly, we review recent genetic approaches and insights into Chlamydomonas cell-cycle regulation that have been enabled by a new generation of genomics-based tools.
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Affiliation(s)
| | - James G Umen
- Donald Danforth Plant Science Center, St. Louis, MO, 63132, USA
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Labandera AM, Vahab AR, Chaudhuri S, Kerk D, Moorhead GBG. The mitotic PP2A regulator ENSA/ARPP-19 is remarkably conserved across plants and most eukaryotes. Biochem Biophys Res Commun 2015; 458:739-44. [PMID: 25666948 DOI: 10.1016/j.bbrc.2015.01.123] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 01/25/2015] [Indexed: 11/25/2022]
Abstract
Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase of eukaryotes. PP2A containing the B55 subunit is a key regulator of mitosis and must be inhibited by phosphorylated α-endosulfine (ENSA) or cyclic AMP-regulated 19 kDa phosphoprotein (ARPP-19) to allow passage through mitosis. Exit from mitosis then requires dephosphorylation of ENSA/ARPP-19 to relieve inhibition of PP2A/B55. ENSA/ARPP-19 has been characterized in several vertebrates and budding yeast, but little is known about its presence in plants and the majority of other eukaryotes. Here we show that three isoforms of ENSA/ARPP-19 are present in the Arabidopsis thaliana genome with distinct expression profiles across various plant tissues. The ENSA/ARPP-19 proteins, and in particular their key inhibitory sequence FDSGDY (FDSADW in plants), is remarkably conserved across plants and most eukaryotes suggesting an ancient origin and conserved function to control PP2A activity.
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Affiliation(s)
- Anne-Marie Labandera
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Ahmad R Vahab
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Sibapriya Chaudhuri
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - David Kerk
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Greg B G Moorhead
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
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