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Chuang CN, Liu HC, Woo TT, Chao JL, Chen CY, Hu HT, Hsueh YP, Wang TF. Noncanonical usage of stop codons in ciliates expands proteins with structurally flexible Q-rich motifs. eLife 2024; 12:RP91405. [PMID: 38393970 PMCID: PMC10942620 DOI: 10.7554/elife.91405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2024] Open
Abstract
Serine(S)/threonine(T)-glutamine(Q) cluster domains (SCDs), polyglutamine (polyQ) tracts and polyglutamine/asparagine (polyQ/N) tracts are Q-rich motifs found in many proteins. SCDs often are intrinsically disordered regions that mediate protein phosphorylation and protein-protein interactions. PolyQ and polyQ/N tracts are structurally flexible sequences that trigger protein aggregation. We report that due to their high percentages of STQ or STQN amino acid content, four SCDs and three prion-causing Q/N-rich motifs of yeast proteins possess autonomous protein expression-enhancing activities. Since these Q-rich motifs can endow proteins with structural and functional plasticity, we suggest that they represent useful toolkits for evolutionary novelty. Comparative Gene Ontology (GO) analyses of the near-complete proteomes of 26 representative model eukaryotes reveal that Q-rich motifs prevail in proteins involved in specialized biological processes, including Saccharomyces cerevisiae RNA-mediated transposition and pseudohyphal growth, Candida albicans filamentous growth, ciliate peptidyl-glutamic acid modification and microtubule-based movement, Tetrahymena thermophila xylan catabolism and meiosis, Dictyostelium discoideum development and sexual cycles, Plasmodium falciparum infection, and the nervous systems of Drosophila melanogaster, Mus musculus and Homo sapiens. We also show that Q-rich-motif proteins are expanded massively in 10 ciliates with reassigned TAAQ and TAGQ codons. Notably, the usage frequency of CAGQ is much lower in ciliates with reassigned TAAQ and TAGQ codons than in organisms with expanded and unstable Q runs (e.g. D. melanogaster and H. sapiens), indicating that the use of noncanonical stop codons in ciliates may have coevolved with codon usage biases to avoid triplet repeat disorders mediated by CAG/GTC replication slippage.
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Affiliation(s)
| | - Hou-Cheng Liu
- Institute of Molecular Biology, Academia SinicaTaipeiTaiwan
| | - Tai-Ting Woo
- Institute of Molecular Biology, Academia SinicaTaipeiTaiwan
| | - Ju-Lan Chao
- Institute of Molecular Biology, Academia SinicaTaipeiTaiwan
| | - Chiung-Ya Chen
- Institute of Molecular Biology, Academia SinicaTaipeiTaiwan
| | - Hisao-Tang Hu
- Institute of Molecular Biology, Academia SinicaTaipeiTaiwan
| | - Yi-Ping Hsueh
- Institute of Molecular Biology, Academia SinicaTaipeiTaiwan
- Department of Biochemical Science and Technology, National Chiayi UniversityChiayiTaiwan
| | - Ting-Fang Wang
- Institute of Molecular Biology, Academia SinicaTaipeiTaiwan
- Department of Biochemical Science and Technology, National Chiayi UniversityChiayiTaiwan
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2
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Wang L, Yang S, Xue Y, Bo T, Xu J, Wang W. Mismatch Repair Protein Msh6 Tt Is Necessary for Nuclear Division and Gametogenesis in Tetrahymena thermophila. Int J Mol Sci 2023; 24:17619. [PMID: 38139447 PMCID: PMC10743813 DOI: 10.3390/ijms242417619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 12/15/2023] [Accepted: 12/16/2023] [Indexed: 12/24/2023] Open
Abstract
DNA mismatch repair (MMR) improves replication accuracy by up to three orders of magnitude. The MutS protein in E. coli or its eukaryotic homolog, the MutSα (Msh2-Msh6) complex, recognizes base mismatches and initiates the mismatch repair mechanism. Msh6 is an essential protein for assembling the heterodimeric complex. However, the function of the Msh6 subunit remains elusive. Tetrahymena undergoes multiple DNA replication and nuclear division processes, including mitosis, amitosis, and meiosis. Here, we found that Msh6Tt localized in the macronucleus (MAC) and the micronucleus (MIC) during the vegetative growth stage and starvation. During the conjugation stage, Msh6Tt only localized in MICs and newly developing MACs. MSH6Tt knockout led to aberrant nuclear division during vegetative growth. The MSH6TtKO mutants were resistant to treatment with the DNA alkylating agent methyl methanesulfonate (MMS) compared to wild type cells. MSH6Tt knockout affected micronuclear meiosis and gametogenesis during the conjugation stage. Furthermore, Msh6Tt interacted with Msh2Tt and MMR-independent factors. Downregulation of MSH2Tt expression affected the stability of Msh6Tt. In addition, MSH6Tt knockout led to the upregulated expression of several MSH6Tt homologs at different developmental stages. Msh6Tt is involved in macronuclear amitosis, micronuclear mitosis, micronuclear meiosis, and gametogenesis in Tetrahymena.
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Affiliation(s)
- Lin Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (L.W.); (S.Y.); (Y.X.); (T.B.)
| | - Sitong Yang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (L.W.); (S.Y.); (Y.X.); (T.B.)
| | - Yuhuan Xue
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (L.W.); (S.Y.); (Y.X.); (T.B.)
| | - Tao Bo
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (L.W.); (S.Y.); (Y.X.); (T.B.)
- Shanxi Key Laboratory of Biotechnology, Taiyuan 030006, China
| | - Jing Xu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (L.W.); (S.Y.); (Y.X.); (T.B.)
- School of Life Science, Shanxi University, Taiyuan 030006, China
| | - Wei Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China; (L.W.); (S.Y.); (Y.X.); (T.B.)
- Shanxi Key Laboratory of Biotechnology, Taiyuan 030006, China
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3
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Wang L, Xue Y, Yang S, Bo T, Xu J, Wang W. Mismatch Repair Protein Msh2 Is Necessary for Macronuclear Stability and Micronuclear Division in Tetrahymena thermophila. Int J Mol Sci 2023; 24:10559. [PMID: 37445734 DOI: 10.3390/ijms241310559] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/20/2023] [Accepted: 06/22/2023] [Indexed: 07/15/2023] Open
Abstract
Mismatch repair (MMR) is a conserved mechanism that is primarily responsible for the repair of DNA mismatches during DNA replication. Msh2 forms MutS heterodimer complexes that initiate the MMR in eukaryotes. The function of Msh2 is less clear under different chromatin structures. Tetrahymena thermophila contains a transcriptionally active macronucleus (MAC) and a transcriptionally silent micronucleus (MIC) in the same cytoplasm. Msh2 is localized in the MAC and MIC during vegetative growth. Msh2 is localized in the perinuclear region around the MIC and forms a spindle-like structure as the MIC divides. During the early conjugation stage, Msh2 is localized in the MIC and disappears from the parental MAC. Msh2 is localized in the new MAC and new MIC during the late conjugation stage. Msh2 also forms a spindle-like structure with a meiotic MIC and mitotic gametic nucleus. MSH2 knockdown inhibits the division of MAC and MIC during vegetative growth and affects cellular proliferation. MSH2 knockdown mutants are sensitive to cisplatin treatment. MSH2 knockdown also affects micronuclear meiosis and gametogenesis during sexual development. Furthermore, Msh2 interacts with MMR-dependent and MMR-independent factors. Therefore, Msh2 is necessary for macronuclear stability, as well as micronuclear mitosis and meiosis in Tetrahymena.
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Affiliation(s)
- Lin Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Yuhuan Xue
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Sitong Yang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Tao Bo
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
- Shanxi Key Laboratory of Biotechnology, Taiyuan 030006, China
| | - Jing Xu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
- School of Life Science, Shanxi University, Taiyuan 030006, China
| | - Wei Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
- Shanxi Key Laboratory of Biotechnology, Taiyuan 030006, China
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4
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Palacios-Blanco I, Martín-Castellanos C. Cyclins and CDKs in the regulation of meiosis-specific events. Front Cell Dev Biol 2022; 10:1069064. [PMID: 36523509 PMCID: PMC9745066 DOI: 10.3389/fcell.2022.1069064] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 11/14/2022] [Indexed: 07/13/2024] Open
Abstract
How eukaryotic cells control their duplication is a fascinating example of how a biological system self-organizes specific activities to temporally order cellular events. During cell cycle progression, the cellular level of CDK (Cyclin-Dependent Kinase) activity temporally orders the different cell cycle phases, ensuring that DNA replication occurs prior to segregation into two daughter cells. CDK activity requires the binding of a regulatory subunit (cyclin) to the core kinase, and both CDKs and cyclins are well conserved throughout evolution from yeast to humans. As key regulators, they coordinate cell cycle progression with metabolism, DNA damage, and cell differentiation. In meiosis, the special cell division that ensures the transmission of genetic information from one generation to the next, cyclins and CDKs have acquired novel functions to coordinate meiosis-specific events such as chromosome architecture, recombination, and synapsis. Interestingly, meiosis-specific cyclins and CDKs are common in evolution, some cyclins seem to have evolved to acquire CDK-independent functions, and even some CDKs associate with a non-cyclin partner. We will review the functions of these key regulators in meiosis where variation has specially flourished.
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5
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Tian M, Cai X, Liu Y, Liucong M, Howard-Till R. A practical reference for studying meiosis in the model ciliate Tetrahymena thermophila. MARINE LIFE SCIENCE & TECHNOLOGY 2022; 4:595-608. [PMID: 37078080 PMCID: PMC10077211 DOI: 10.1007/s42995-022-00149-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 09/28/2022] [Indexed: 05/03/2023]
Abstract
Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction. Abnormalities in meiosis are often causes of infertility and birth defects (e.g., Down syndrome). Most organisms use a highly specialized zipper-like protein complex, the synaptonemal complex (SC), to guide and stabilize pairing of homologous chromosomes in meiosis. Although the SC is critical for meiosis in many eukaryotes, there are organisms that perform meiosis without a functional SC. However, such SC-less meiosis is poorly characterized. To understand the features of SC-less meiosis and its adaptive significance, the ciliated protozoan Tetrahymena was selected as a model. Meiosis research in Tetrahymena has revealed intriguing aspects of the regulatory programs utilized in its SC-less meiosis, yet additional efforts are needed for obtaining an in-depth comprehension of mechanisms that are associated with the absence of SC. Here, aiming at promoting a wider application of Tetrahymena for meiosis research, we introduce basic concepts and core techniques for studying meiosis in Tetrahymena and then suggest future directions for expanding the current Tetrahymena meiosis research toolbox. These methodologies could be adopted for dissecting meiosis in poorly characterized ciliates that might reveal novel features. Such data will hopefully provide insights into the function of the SC and the evolution of meiosis from a unique perspective. Supplementary Information The online version contains supplementary material available at 10.1007/s42995-022-00149-8.
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Affiliation(s)
- Miao Tian
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
- Institute of Human Genetics, CNRS, University of Montpellier, 34090 Montpellier, France
| | - Xia Cai
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Yujie Liu
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Mingmei Liucong
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Rachel Howard-Till
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA USA
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6
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Zhang J, Tian M, Chen K, Yan G, Xiong J, Miao W. Zfp1, a Cys2His2 zinc finger protein is required for meiosis initiation in Tetrahymena thermophila. Cell Cycle 2022; 21:1422-1433. [PMID: 35293272 PMCID: PMC9345619 DOI: 10.1080/15384101.2022.2053449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Meiosis is an important and highly conserved process that occurs during eukaryotic sexual reproduction. Diverse mechanisms are responsible for meiosis initiation among eukaryotes, and transcription factors have been established to have an important role in many species. However, the specific function of transcription factors in initiating meiosis in ciliates is unknown. Here we show that a putative Cys2His2 zinc finger-containing transcription factor encoded by the ZFP1 gene is specifically expressed during sexual reproduction in Tetrahymena thermophila. Meiosis is not initiated in the cells lacking ZFP1. Transcriptome sequencing analyses reveal that Zfp1 is required for the expression of many meiosis-specific genes. Our results indicate that Zfp1 could be a transcriptional activator required for meiosis initiation in T. thermophila.
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Affiliation(s)
- Jing Zhang
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Miao Tian
- Department of Chromosome Biology and Max F. Perutz Laboratories, Center for Molecular Biology, University of Vienna, Vienna, Austria
| | - Kai Chen
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Guanxiong Yan
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China.,College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, Shanghai, China
| | - Jie Xiong
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Wei Miao
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China.,State Key Laboratory of Freshwater Ecology and Biotechnology of China, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China.,CAS Center for Excellence in Animal Evolution and Genetics, Kunming, Yunnan, China
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7
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Identification and utilization of a mutated 60S ribosomal subunit coding gene as an effective and cost-efficient selection marker for Tetrahymena genetic manipulation. Int J Biol Macromol 2022; 204:1-8. [PMID: 35122796 DOI: 10.1016/j.ijbiomac.2022.01.188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 01/05/2023]
Abstract
Since the onset of molecular biology, the ciliate Tetrahymena thermophila has been one of the most convenient single-celled model eukaryotes for genetics, biochemistry, and cell biology. Particularly, thanks to the availability of several different selection markers, it is possible to knock out or knock in genes at multiple genetic loci simultaneously in Tetrahymena, which makes it an excellent model ciliate for tackling complex regulatory mechanisms. Despite these selection markers are efficient for genetic manipulation, the costly drugs used for selection have highlighted the urgent demand for an additional cost-efficient and effective selection marker. Here, we found that a mutated 60S ribosomal subunit component, RPL36A, confers T. thermophila with cycloheximide resistance. On top of that, we developed a cycloheximide cassette and explored suitable transformation and selection conditions. Using the new cassette, we obtained both knockout and knock-in strains successfully at a relatively low cost. This study also provided the first evidence that a cycloheximide resistance gene can be engineered as a selection marker to completely delete a gene from the highly-polyploid somatic nucleus in Tetrahymena.
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8
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Lian Y, Hao H, Xu J, Bo T, Liang A, Wang W. The histone chaperone Nrp1 is required for chromatin stability and nuclear division in Tetrahymena thermophila. Epigenetics Chromatin 2021; 14:34. [PMID: 34301312 PMCID: PMC8299592 DOI: 10.1186/s13072-021-00409-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 07/06/2021] [Indexed: 12/23/2022] Open
Abstract
Histone chaperones facilitate DNA replication and repair by promoting chromatin assembly, disassembly and histone exchange. Following histones synthesis and nucleosome assembly, the histones undergo posttranslational modification by different enzymes and are deposited onto chromatins by various histone chaperones. In Tetrahymena thermophila, histones from macronucleus (MAC) and micronucleus (MIC) have been comprehensively investigated, but the function of histone chaperones remains unclear. Histone chaperone Nrp1 in Tetrahymena contains four conserved tetratricopepeptide repeat (TPR) domains and one C-terminal nuclear localization signal. TPR2 is typically interrupted by a large acidic motif. Immunofluorescence staining showed that Nrp1 is located in the MAC and MICs, but disappeared in the apoptotic parental MAC and the degraded MICs during the conjugation stage. Nrp1 was also colocalized with α-tubulin around the spindle structure. NRP1 knockdown inhibited cellular proliferation and led to the loss of chromosome, abnormal macronuclear amitosis, and disorganized micronuclear mitosis during the vegetative growth stage. During sexual developmental stage, the gametic nuclei failed to be selected and abnormally degraded in NRP1 knockdown mutants. Affinity purification combined with mass spectrometry analysis indicated that Nrp1 is co-purified with core histones, heat shock proteins, histone chaperones, and DNA damage repair proteins. The physical direct interaction of Nrp1 and Asf1 was also confirmed by pull-down analysis in vitro. The results show that histone chaperone Nrp1 is involved in micronuclear mitosis and macronuclear amitosis in the vegetative growth stage and maintains gametic nuclei formation during the sexual developmental stage. Nrp1 is required for chromatin stability and nuclear division in Tetrahymena thermophila.
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Affiliation(s)
- Yinjie Lian
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China
| | - Huijuan Hao
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China
| | - Jing Xu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China.,School of Life Science, Shanxi University, Taiyuan, 030006, China
| | - Tao Bo
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China
| | - Aihua Liang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China
| | - Wei Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd., Taiyuan, 030006, China.
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9
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Bustamante-Jaramillo LF, Ramos C, Martín-Castellanos C. The Meiosis-Specific Crs1 Cyclin Is Required for Efficient S-Phase Progression and Stable Nuclear Architecture. Int J Mol Sci 2021; 22:ijms22115483. [PMID: 34067465 PMCID: PMC8196990 DOI: 10.3390/ijms22115483] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/13/2021] [Accepted: 05/19/2021] [Indexed: 11/26/2022] Open
Abstract
Cyclins and CDKs (Cyclin Dependent Kinases) are key players in the biology of eukaryotic cells, representing hubs for the orchestration of physiological conditions with cell cycle progression. Furthermore, as in the case of meiosis, cyclins and CDKs have acquired novel functions unrelated to this primal role in driving the division cycle. Meiosis is a specialized developmental program that ensures proper propagation of the genetic information to the next generation by the production of gametes with accurate chromosome content, and meiosis-specific cyclins are widespread in evolution. We have explored the diversification of CDK functions studying the meiosis-specific Crs1 cyclin in fission yeast. In addition to the reported role in DSB (Double Strand Break) formation, this cyclin is required for meiotic S-phase progression, a canonical role, and to maintain the architecture of the meiotic chromosomes. Crs1 localizes at the SPB (Spindle Pole Body) and is required to stabilize the cluster of telomeres at this location (bouquet configuration), as well as for normal SPB motion. In addition, Crs1 exhibits CDK(Cdc2)-dependent kinase activity in a biphasic manner during meiosis, in contrast to a single wave of protein expression, suggesting a post-translational control of its activity. Thus, Crs1 displays multiple functions, acting both in cell cycle progression and in several key meiosis-specific events.
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New contribution to epigenetic studies: Isolation of micronuclei with high purity and DNA integrity in the model ciliated protist, Tetrahymena thermophila. Eur J Protistol 2021; 80:125804. [PMID: 34062315 DOI: 10.1016/j.ejop.2021.125804] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 03/31/2021] [Accepted: 05/04/2021] [Indexed: 10/24/2022]
Abstract
The ciliated protist Tetrahymena thermophila is a well-known model organism with typical nuclear dimorphism containing a somatic macronucleus (MAC) and a germline micronucleus (MIC). The presence in the same cell compartment of two nuclei with distinctly different structural and functional properties provides an ideal model system to explore mechanisms of genome maintenance. Although methods for the isolation of MIC have been available for many years, cross-contamination and DNA degradation remain unresolved. Here, we describe a reliable and quick method to isolate MIC with high purity and DNA integrity in T. thermophila. Different factors are examined to optimize the MIC purification. The MAC contamination ratio in purified MIC is about 0.19% and DNA integrity of purified MIC is maintained. We also establish a more accurate method to detect the contamination rate of nuclei including microscopic observation and PCR detection. This study will facilitate further epigenetic research in Tetrahymena.
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Biodiversity-based development and evolution: the emerging research systems in model and non-model organisms. SCIENCE CHINA-LIFE SCIENCES 2021; 64:1236-1280. [PMID: 33893979 DOI: 10.1007/s11427-020-1915-y] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 03/16/2021] [Indexed: 02/07/2023]
Abstract
Evolutionary developmental biology, or Evo-Devo for short, has become an established field that, broadly speaking, seeks to understand how changes in development drive major transitions and innovation in organismal evolution. It does so via integrating the principles and methods of many subdisciplines of biology. Although we have gained unprecedented knowledge from the studies on model organisms in the past decades, many fundamental and crucially essential processes remain a mystery. Considering the tremendous biodiversity of our planet, the current model organisms seem insufficient for us to understand the evolutionary and physiological processes of life and its adaptation to exterior environments. The currently increasing genomic data and the recently available gene-editing tools make it possible to extend our studies to non-model organisms. In this review, we review the recent work on the regulatory signaling of developmental and regeneration processes, environmental adaptation, and evolutionary mechanisms using both the existing model animals such as zebrafish and Drosophila, and the emerging nonstandard model organisms including amphioxus, ascidian, ciliates, single-celled phytoplankton, and marine nematode. In addition, the challenging questions and new directions in these systems are outlined as well.
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12
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Liu Y, Nan B, Niu J, Kapler GM, Gao S. An Optimized and Versatile Counter-Flow Centrifugal Elutriation Workflow to Obtain Synchronized Eukaryotic Cells. Front Cell Dev Biol 2021; 9:664418. [PMID: 33959616 PMCID: PMC8093812 DOI: 10.3389/fcell.2021.664418] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/23/2021] [Indexed: 11/21/2022] Open
Abstract
Cell synchronization is a powerful tool to understand cell cycle events and its regulatory mechanisms. Counter-flow centrifugal elutriation (CCE) is a more generally desirable method to synchronize cells because it does not significantly alter cell behavior and/or cell cycle progression, however, adjusting specific parameters in a cell type/equipment-dependent manner can be challenging. In this paper, we used the unicellular eukaryotic model organism, Tetrahymena thermophila as a testing system for optimizing CCE workflow. Firstly, flow cytometry conditions were identified that reduced nuclei adhesion and improved the assessment of cell cycle stage. We then systematically examined how to achieve the optimal conditions for three critical factors affecting the outcome of CCE, including loading flow rate, collection flow rate and collection volume. Using our optimized workflow, we obtained a large population of highly synchronous G1-phase Tetrahymena as measured by 5-ethynyl-2'-deoxyuridine (EdU) incorporation into nascent DNA strands, bulk DNA content changes by flow cytometry, and cell cycle progression by light microscopy. This detailed protocol can be easily adapted to synchronize other eukaryotic cells.
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Affiliation(s)
- Yongqiang Liu
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Bei Nan
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Junhua Niu
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Geoffrey M. Kapler
- Department of Molecular and Cellular Medicine, Texas A&M University, College Station, TX, United States
| | - Shan Gao
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
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13
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The Compact Macronuclear Genome of the Ciliate Halteria grandinella: A Transcriptome-Like Genome with 23,000 Nanochromosomes. mBio 2021; 12:mBio.01964-20. [PMID: 33500338 PMCID: PMC7858049 DOI: 10.1128/mbio.01964-20] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
How to achieve protein diversity by genome and transcriptome processing is essential for organismal complexity and adaptation. The present work identifies that the macronuclear genome of Halteria grandinella, a cosmopolitan unicellular eukaryote, is composed almost entirely of gene-sized nanochromosomes with extremely short nongenic regions. How to achieve protein diversity by genome and transcriptome processing is essential for organismal complexity and adaptation. The present work identifies that the macronuclear genome of Halteria grandinella, a cosmopolitan unicellular eukaryote, is composed almost entirely of gene-sized nanochromosomes with extremely short nongenic regions. This challenges our usual understanding of chromosomal structure and suggests the possibility of novel mechvanisms in transcriptional regulation. Comprehensive analysis of multiple data sets reveals that Halteria transcription dynamics are influenced by: (i) nonuniform nanochromosome copy numbers correlated with gene-expression level; (ii) dynamic alterations at both the DNA and RNA levels, including alternative internal eliminated sequence (IES) deletions during macronucleus formation and large-scale alternative splicing in transcript maturation; and (iii) extremely short 5′ and 3′ untranslated regions (UTRs) and universal TATA box-like motifs in the compact 5′ subtelomeric regions of most chromosomes. This study broadens the view of ciliate biology and the evolution of unicellular eukaryotes, and identifies Halteria as one of the most compact known eukaryotic genomes, indicating that complex cell structure does not require complex gene architecture.
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Further insights into the phylogeny of peniculid ciliates (Ciliophora, Oligohymenophorea) based on multigene data. Mol Phylogenet Evol 2020; 154:107003. [PMID: 33137410 DOI: 10.1016/j.ympev.2020.107003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 10/25/2020] [Accepted: 10/27/2020] [Indexed: 12/31/2022]
Abstract
Peniculids comprise a large order of ciliated protists in Class Oligohymenophorea having many unresolved evolutionary relationships. Herein, we report 27 new sequences, including 18S rRNA, ITS1-5.8S- ITS2 rRNA, 28S rRNA and the mitochondrial cox1 genes of eight peniculids. We conducted phylogenetic analyses based on each these markers and on a four-gene concatenated data set (18S rRNA, ITS1-5.8S- ITS2 rRNA, 28S rRNA, and cox1 gene). The main findings are: 1) subclass Peniculia and family Parameciidae are monophyletic, with genus Frontonia remaining non-monophyletic; 2) Urocentrids have traditionally been regarded as a family, multi-gene analyses support the rank of Urocentrida and consistently recovers this order as sister to Peniculida, and Urocentrida and Peniculida comprise subclass Peniculia in agreement with Lynn's (2008) classification; 3) discrepancies between multiple-gene phylogenies, and conflicts with morphologic data regarding genus Frontonia necessitate expansion and revision of species diagnoses and we propose consideration of Group III of Frontonia (including F. didieri, F. ocularis, F. anatolica, F. pusilla and F. elegans) as incertae sedis in Peniculida; 4) multi-gene analyses of Parameciidae support five previously established subgenera. Paramecium buetschlii is placed in subgenus Chloroparamecium, and P. chlorelligerum into subgenus Viridoparamecium.
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Wang Y, Sheng Y, Liu Y, Zhang W, Cheng T, Duan L, Pan B, Qiao Y, Liu Y, Gao S. A distinct class of eukaryotic MT-A70 methyltransferases maintain symmetric DNA N6-adenine methylation at the ApT dinucleotides as an epigenetic mark associated with transcription. Nucleic Acids Res 2020; 47:11771-11789. [PMID: 31722409 PMCID: PMC7145601 DOI: 10.1093/nar/gkz1053] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 10/21/2019] [Accepted: 10/24/2019] [Indexed: 12/18/2022] Open
Abstract
Rediscovered as a potential eukaryotic epigenetic mark, DNA N6-adenine methylation (6mA) varies across species in abundance and its relationships with transcription. Here we characterize AMT1—representing a distinct MT-A70 family methyltransferase—in the ciliate Tetrahymena thermophila. AMT1 loss-of-function leads to severe defects in growth and development. Single Molecule, Real-Time (SMRT) sequencing reveals that AMT1 is required for the bulk of 6mA and all symmetric methylation at the ApT dinucleotides. The detection of hemi-methylated ApT sites suggests a semi-conservative mechanism for maintaining symmetric methylation. AMT1 affects expression of many genes; in particular, RAB46, encoding a Rab family GTPase involved in contractile vacuole function, is likely a direct target. The distribution of 6mA resembles H3K4 methylation and H2A.Z, two conserved epigenetic marks associated with RNA polymerase II transcription. Furthermore, strong 6mA and nucleosome positioning in wild-type cells is attenuated in ΔAMT1 cells. Our results support that AMT1-catalyzed 6mA is an integral part of the transcription-associated epigenetic landscape. AMT1 homologues are generally found in protists and basal fungi featuring ApT hyper-methylation associated with transcription, which are missing in animals, plants, and true fungi. This dichotomy of 6mA functions and the underlying molecular mechanisms may have implications in eukaryotic diversification.
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Affiliation(s)
- Yuanyuan Wang
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Yalan Sheng
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Yongqiang Liu
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Wenxin Zhang
- School of Life Science, Anhui Agricultural University, Hefei 230036, China
| | - Ting Cheng
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Lili Duan
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Bo Pan
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Yu Qiao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Yifan Liu
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Shan Gao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
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The completed macronuclear genome of a model ciliate Tetrahymena thermophila and its application in genome scrambling and copy number analyses. SCIENCE CHINA-LIFE SCIENCES 2020; 63:1534-1542. [PMID: 32297047 DOI: 10.1007/s11427-020-1689-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 03/26/2020] [Indexed: 01/03/2023]
Abstract
The ciliate Tetrahymena thermophila has been a powerful model system for molecular and cellular biology. However, some investigations have been limited due to the incomplete closure and sequencing of the macronuclear genome assembly, which for many years has been stalled at 1,158 scaffolds, with large sections of unknown sequences (available in Tetrahymena Genome Database, TGD, http://ciliate.org/ ). Here we completed the first chromosome-level Tetrahymena macronuclear genome assembly, with approximately 300× long Single Molecule, Real-Time reads of the wild-type SB210 cells-the reference strain for the initial macronuclear genome sequencing project. All 181 chromosomes were capped with two telomeres and gaps were entirely closed. The completed genome shows significant improvements over the current assembly (TGD 2014) in both chromosome structure and sequence integrity. The majority of previously identified gene models shown in TGD were retained, with the addition of 36 new genes and 883 genes with modified gene models. The new genome and annotation were incorporated into TGD. This new genome allows for pursuit in some underexplored areas that were far more challenging previously; two of them, genome scrambling and chromosomal copy number, were investigated in this study. We expect that the completed macronuclear genome will facilitate many studies in Tetrahymena biology, as well as multiple lines of research in other eukaryotes.
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Wang Y, Jiang Y, Liu Y, Li Y, Katz LA, Gao F, Yan Y. Comparative Studies on the Polymorphism and Copy Number Variation of mtSSU rDNA in Ciliates (Protista, Ciliophora): Implications for Phylogenetic, Environmental, and Ecological Research. Microorganisms 2020; 8:E316. [PMID: 32106521 PMCID: PMC7142639 DOI: 10.3390/microorganisms8030316] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 02/20/2020] [Accepted: 02/21/2020] [Indexed: 01/21/2023] Open
Abstract
While nuclear small subunit ribosomal DNA (nSSU rDNA) is the most commonly-used gene marker in studying phylogeny, ecology, abundance, and biodiversity of microbial eukaryotes, mitochondrial small subunit ribosomal DNA (mtSSU rDNA) provides an alternative. Recently, both copy number variation and sequence variation of nSSU rDNA have been demonstrated for diverse organisms, which can contribute to misinterpretation of microbiome data. Given this, we explore patterns for mtSSU rDNA among 13 selected ciliates (representing five classes), a major component of microbial eukaryotes, estimating copy number and sequence variation and comparing to that of nSSU rDNA. Our study reveals: (1) mtSSU rDNA copy number variation is substantially lower than that for nSSU rDNA; (2) mtSSU rDNA copy number ranges from 1.0 × 104 to 8.1 × 105; (3) a most common sequence of mtSSU rDNA is also found in each cell; (4) the sequence variation of mtSSU rDNA are mainly indels in poly A/T regions, and only half of species have sequence variation, which is fewer than that for nSSU rDNA; and (5) the polymorphisms between haplotypes of mtSSU rDNA would not influence the phylogenetic topology. Together, these data provide more insights into mtSSU rDNA as a powerful marker especially for microbial ecology studies.
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Affiliation(s)
- Yurui Wang
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; (Y.W.); (Y.J.); (Y.L.); (Y.L.); (F.G.)
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
| | - Yaohan Jiang
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; (Y.W.); (Y.J.); (Y.L.); (Y.L.); (F.G.)
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
| | - Yongqiang Liu
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; (Y.W.); (Y.J.); (Y.L.); (Y.L.); (F.G.)
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
| | - Yuan Li
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; (Y.W.); (Y.J.); (Y.L.); (Y.L.); (F.G.)
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
| | - Laura A. Katz
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA;
| | - Feng Gao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; (Y.W.); (Y.J.); (Y.L.); (Y.L.); (F.G.)
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
| | - Ying Yan
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; (Y.W.); (Y.J.); (Y.L.); (Y.L.); (F.G.)
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA;
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18
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Gao Y, Gong R, Jiang Y, Pan B, Li Y, Warren A, Jiang J, Gao F. Morphogenetic characters of the model ciliate Euplotes vannus (Ciliophora, Spirotrichea): Notes on cortical pattern formation during conjugational and postconjugational reorganization. Eur J Protistol 2020; 73:125675. [PMID: 32036251 DOI: 10.1016/j.ejop.2020.125675] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 01/12/2020] [Accepted: 01/21/2020] [Indexed: 11/26/2022]
Abstract
Ciliated protists represent a morphologically and genetically distinct group of single-celled eukaryotes which can reproduce asexually and sexually. Morphogenesis occurs in both asexual and sexual modes of reproduction which is of interest for researchers investigating cell differentiation, regeneration, systematics and evolution. However, studies of morphogenesis have concentrated almost entirely on the asexual mode. Here we use protargol staining to investigate the morphogenetic processes during sexual reproduction in the model species Euplotes vannus (Müller). The major events include: (1) two rounds of morphogenesis occur during sexual reproduction, i.e., conjugational and postconjugational reorganization; (2) in both processes the oral primordium is generated de novo in a pouch beneath the cortex; (3) the frontoventral-transverse cirri anlagen are formed de novo and fragment in a 3:3:3:3:2 pattern; (4) the leftmost cirrus and the paroral membrane do not change during conjugational morphogenesis, but reorganize de novo during postconjugational morphogenesis; (5) marginal cirral anlagen are formed de novo in both morphogenetic processes; (6) two or three caudal cirri are formed at the ends of the rightmost two or three old dorsal kineties; (7) the dorsal kineties are retained entirely. These results can serve as reference to investigate the morphogenetic events in the different stages of sexual reproduction.
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Affiliation(s)
- Yunyi Gao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Ruitao Gong
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Yaohan Jiang
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Bo Pan
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Yuan Li
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Alan Warren
- Department of Life Sciences, Natural History Museum, London SW7 5BD, United Kingdom
| | - Jiamei Jiang
- Shanghai Universities Key Laboratory of Marine Animal Taxonomy and Evolution, Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China.
| | - Feng Gao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China.
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19
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Conjugation in Euplotes raikovi (Protista, Ciliophora): New Insights into Nuclear Events and Macronuclear Development from Micronucleate and Amicronucleate Cells. Microorganisms 2020; 8:microorganisms8020162. [PMID: 31979289 PMCID: PMC7074782 DOI: 10.3390/microorganisms8020162] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 01/16/2020] [Accepted: 01/20/2020] [Indexed: 01/08/2023] Open
Abstract
Ciliates form a distinct group of single-celled eukaryotes that host two types of nuclei (micro and macronucleus) in the same cytoplasm and have a special sexual process known as conjugation, which involves mitosis, meiosis, fertilization, nuclear differentiation, and development. Due to their high species diversity, ciliates have evolved different patterns of nuclear events during conjugation. In the present study, we investigate these events in detail in the marine species Euplotes raikovi. Our results indicate that: (i) conjugation lasts for about 50 h, the longest stage being the development of the new macronucleus (ca. 36 h); (ii) there are three prezygotic micronuclear divisions (mitosis and meiosis I and II) and two postzygotic synkaryon divisions; and (iii) a fragment of the parental macronucleus fuses with the new developing macronucleus. In addition, we describe for the first time conjugation in amicronucleate E. raikovi cells. When two amicronucleate cells mate, they separate after about 4 h without evident nuclear changes; when one amicronucleate cell mates with a micronucleate cell, the micronucleus undergoes regular prezygotic divisions to form migratory and stationary pronuclei, but the two pronuclei fuse in the same cell. In the amicronucleate cell, the parental macronucleus breaks into fragments, which are then recovered to form a new functional macronucleus. These results add new information on the process of conjugation in both micronucleate and amicronucleate Euplotes cells.
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20
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Comparative Transcriptome Analyses during the Vegetative Cell Cycle in the Mono-Cellular Organism Pseudokeronopsis erythrina (Alveolata, Ciliophora). Microorganisms 2020; 8:microorganisms8010108. [PMID: 31940957 PMCID: PMC7022673 DOI: 10.3390/microorganisms8010108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/08/2020] [Accepted: 01/09/2020] [Indexed: 01/18/2023] Open
Abstract
Studies focusing on molecular mechanisms of cell cycles have been lagging in unicellular eukaryotes compared to other groups. Ciliates, a group of unicellular eukaryotes, have complex cell division cycles characterized by multiple events. During their vegetative cell cycle, ciliates undergo macronuclear amitosis, micronuclear mitosis, stomatogenesis and somatic cortex morphogenesis, and cytokinesis. Herein, we used the hypotrich ciliate Pseudokeronopsis erythrina, whose morphogenesis has been well studied, to examine molecular mechanisms of ciliate vegetative cell cycles. Single-cell transcriptomes of the growth (G) and cell division (D) stages were compared. The results showed that (i) More than 2051 significantly differentially expressed genes (DEGs) were detected, among which 1545 were up-regulated, while 256 were down-regulated at the D stage. Of these, 11 randomly picked DEGs were validated by reverse transcription quantitative polymerase chain reaction (RT-qPCR); (ii) Enriched DEGs during the D stage of the vegetative cell cycle of P. erythrina were involved in development, cortex modifications, and several organelle-related biological processes, showing correspondence of molecular evidence to morphogenetic changes for the first time; (iii) Several individual components of molecular mechanisms of ciliate vegetative division, the sexual cell cycle and cellular regeneration overlap; and (iv) The P. erythrina cell cycle and division have the same essential components as other eukaryotes, including cyclin-dependent kinases (CDKs), cyclins, and genes closely related to cell proliferation, indicating the conserved nature of this biological process. Further studies are needed focusing on detailed inventory and gene interactions that regulate specific ciliated cell-phase events.
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Cyclin B3 is dispensable for mouse spermatogenesis. Chromosoma 2019; 128:473-487. [PMID: 31446450 DOI: 10.1007/s00412-019-00725-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 08/09/2019] [Accepted: 08/14/2019] [Indexed: 10/26/2022]
Abstract
Cyclins, as regulatory partners of cyclin-dependent kinases (CDKs), control the switch-like cell cycle transitions that orchestrate orderly duplication and segregation of genomes. Compared to mitosis, relatively little is known about how cyclin-CDK complexes control meiosis, the specialized cell division that generates gametes for sexual production. Mouse cyclin B3 was previously shown to have expression restricted to the beginning of meiosis, making it a candidate to regulate meiotic events. Indeed, female mice lacking cyclin B3 are sterile because oocytes arrest at the metaphase-to-anaphase transition of meiosis I. However, whether cyclin B3 functions during spermatogenesis was untested. Here, we found that males lacking cyclin B3 are fertile and show no detectable defects in spermatogenesis based on histological analysis of seminiferous tubules. Cytological analysis further showed no detectable defects in homologous chromosome synapsis or meiotic progression, and suggested that recombination is initiated and completed efficiently. Moreover, absence of cyclin B3 did not exacerbate previously described meiotic defects in mutants deficient for cyclin E2, suggesting a lack of redundancy between these cyclins. Thus, unlike in females, cyclin B3 is not essential for meiosis in males despite its prominent meiosis-specific expression.
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Zhang T, Fan X, Gao F, Al-Farraj SA, El-Serehy HA, Song W. Further analyses on the phylogeny of the subclass Scuticociliatia (Protozoa, Ciliophora) based on both nuclear and mitochondrial data. Mol Phylogenet Evol 2019; 139:106565. [PMID: 31326515 DOI: 10.1016/j.ympev.2019.106565] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 07/13/2019] [Accepted: 07/17/2019] [Indexed: 11/24/2022]
Abstract
So far, the phylogenetic studies on ciliated protists have mainly based on single locus, the nuclear ribosomal DNA (rDNA). In order to avoid the limitations of single gene/genome trees and to add more data to systematic analyses, information from mitochondrial DNA sequence has been increasingly used in different lineages of ciliates. The systematic relationships in the subclass Scuticociliatia are extremely confused and largely unresolved based on nuclear genes. In the present study, we have characterized 72 new sequences, including 40 mitochondrial cytochrome oxidase c subunit I (COI) sequences, 29 mitochondrial small subunit ribosomal DNA (mtSSU-rDNA) sequences and three nuclear small subunit ribosomal DNA (nSSU-rDNA) sequences from 47 isolates of 44 morphospecies. Phylogenetic analyses based on single gene as well as concatenated data were performed and revealed: (1) compared to mtSSU-rDNA, COI gene reveals more consistent relationships with those of nSSU-rDNA; (2) the secondary structures of mtSSU-rRNA V4 region are predicted and compared in scuticociliates, which can contribute to discrimination of closely related species; (3) neither nuclear nor mitochondrial data support the monophyly of the order Loxocephalida, which may represent some divergent and intermediate lineages between the subclass Scuticociliatia and Hymenostomatia; (4) the assignments of thigmotrichids to the order Pleuronematida and the confused taxon Sulcigera comosa to the genus Histiobalantium are confirmed by mitochondrial genes; (5) both nuclear and mitochondrial data reveal that the species in the family Peniculistomatidae always group in the genus Pleuronema, suggesting that peniculistomatids are more likely evolved from Pleuronema-like ancestors; (6) mitochondrial genes support the monophyly of the order Philasterida, but the relationships among families of the order Philasterida remain controversial due to the discrepancies between their morphological and molecular data.
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Affiliation(s)
- Tengteng Zhang
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Xinpeng Fan
- School of Life Sciences, East China Normal University, Shanghai 200241 China
| | - Feng Gao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China.
| | - Saleh A Al-Farraj
- Zoology Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
| | - Hamed A El-Serehy
- Zoology Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
| | - Weibo Song
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.
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