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Jin D, Li C, Chen X, Byerly A, Stover NA, Zhang T, Shao C, Wang Y. Comparative genome analysis of three euplotid protists provides insights into the evolution of nanochromosomes in unicellular eukaryotic organisms. MARINE LIFE SCIENCE & TECHNOLOGY 2023; 5:300-315. [PMID: 37637252 PMCID: PMC10449743 DOI: 10.1007/s42995-023-00175-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 04/12/2023] [Indexed: 08/29/2023]
Abstract
One of the most diverse clades of ciliated protozoa, the class Spirotrichea, displays a series of unique characters in terms of eukaryotic macronuclear (MAC) genome, including high fragmentation that produces nanochromosomes. However, the genomic diversity and evolution of nanochromosomes and gene families for spirotrich MAC genomes are poorly understood. In this study, we assemble the MAC genome of a representative euplotid (a new model organism in Spirotrichea) species, Euplotes aediculatus. Our results indicate that: (a) the MAC genome includes 35,465 contigs with a total length of 97.3 Mb and a contig N50 of 3.4 kb, and contains 13,145 complete nanochromosomes and 43,194 predicted genes, with the majority of these nanochromosomes containing tiny introns and harboring only one gene; (b) genomic comparisons between E. aediculatus and other reported spirotrichs indicate that average GC content and genome fragmentation levels exhibit interspecific variation, and chromosome breaking sites (CBSs) might be lost during evolution, resulting in the increase of multi-gene nanochromosome; (c) gene families associated with chitin metabolism and FoxO signaling pathway are expanded in E. aediculatus, suggesting their potential roles in environment adaptation and survival strategies of E. aediculatus; and (d) a programmed ribosomal frameshift (PRF) with a conservative motif 5'-AAATAR-3' tends to occur in longer genes with more exons, and PRF genes play an important role in many cellular regulation processes. Supplementary Information The online version contains supplementary material available at 10.1007/s42995-023-00175-0.
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Affiliation(s)
- Didi Jin
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi’an, 710119 China
| | - Chao Li
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
| | - Xiao Chen
- Laboratory of Marine Protozoan Biodiversity and Evolution, Marine College, Shandong University, Weihai, 264209 China
| | - Adam Byerly
- Department of Computer Science and Information Systems, Bradley University, Peoria, 61625 USA
| | - Naomi A. Stover
- Department of Biology, Bradley University, Peoria, 61625 USA
| | - Tengteng Zhang
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi’an, 710119 China
| | - Chen Shao
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi’an, 710119 China
| | - Yurui Wang
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi’an, 710119 China
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Chen Z, Li J, Salas-Leiva DE, Chen M, Chen S, Li S, Wu Y, Yi Z. Group-specific functional patterns of mitochondrion-related organelles shed light on their multiple transitions from mitochondria in ciliated protists. MARINE LIFE SCIENCE & TECHNOLOGY 2022; 4:609-623. [PMID: 37078085 PMCID: PMC10077286 DOI: 10.1007/s42995-022-00147-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 09/23/2022] [Indexed: 05/03/2023]
Abstract
Adaptations of ciliates to hypoxic environments have arisen independently several times. Studies on mitochondrion-related organelle (MRO) metabolisms from distinct anaerobic ciliate groups provide evidence for understanding the transitions from mitochondria to MROs within eukaryotes. To deepen our knowledge about the evolutionary patterns of ciliate anaerobiosis, mass-culture and single-cell transcriptomes of two anaerobic species, Metopus laminarius (class Armophorea) and Plagiopyla cf. narasimhamurtii (class Plagiopylea), were sequenced and their MRO metabolic maps were compared. In addition, we carried out comparisons using publicly available predicted MRO proteomes from other ciliate classes (i.e., Armophorea, Litostomatea, Muranotrichea, Oligohymenophorea, Parablepharismea and Plagiopylea). We found that single-cell transcriptomes were similarly comparable to their mass-culture counterparts in predicting MRO metabolic pathways of ciliates. The patterns of the components of the MRO metabolic pathways might be divergent among anaerobic ciliates, even among closely related species. Notably, our findings indicate the existence of group-specific functional relics of electron transport chains (ETCs). Detailed group-specific ETC functional patterns are as follows: full oxidative phosphorylation in Oligohymenophorea and Muranotrichea; only electron-transfer machinery in Armophorea; either of these functional types in Parablepharismea; and ETC functional absence in Litostomatea and Plagiopylea. These findings suggest that adaptation of ciliates to anaerobic conditions is group-specific and has occurred multiple times. Our results also show the potential and the limitations of detecting ciliate MRO proteins using single-cell transcriptomes and improve the understanding of the multiple transitions from mitochondria to MROs within ciliates. Supplementary Information The online version contains supplementary material available at 10.1007/s42995-022-00147-w.
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Affiliation(s)
- Zhicheng Chen
- Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, 510631 China
| | - Jia Li
- Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, 510631 China
| | | | - Miaoying Chen
- Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, 510631 China
| | - Shilong Chen
- Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, 510631 China
| | - Senru Li
- Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, 510631 China
| | - Yanyan Wu
- Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, 510631 China
| | - Zhenzhen Yi
- Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory for Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, 510631 China
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Fu J, Chi Y, Lu X, Gao F, Al-Farraj SA, Petroni G, Jiang J. Doublets of the unicellular organism Euplotes vannus (Alveolata, Ciliophora, Euplotida): the morphogenetic patterns of the ciliary and nuclear apparatuses associated with cell division. MARINE LIFE SCIENCE & TECHNOLOGY 2022; 4:527-535. [PMID: 37078083 PMCID: PMC10077243 DOI: 10.1007/s42995-022-00150-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 10/05/2022] [Indexed: 05/03/2023]
Abstract
Ciliated protists are one of the most diverse and highly differentiated group among unicellular organisms. Doublets occur in ciliates when two cells fuse into a single individual. Doublets contain two major cellular components (either cell in a doublet) and have traditionally been considered as developmental anomalies. Nevertheless, doublets can divide or even conjugate effectively, which may represent dispersal forms of the life stages. In addition, morphogenesis, as an important process in the life cycle, will provide important insights into the complex differentiation mechanism and various physiological phenomena. However, morphogenetic studies focusing on doublets of ciliates are very limited, which has become an obstacle to understand their complete life history. Here we isolated a doublet strain from the marine species Euplotes vannus (Müller, 1786) Diesing, 1850 and investigated its morphogenetic events during asexual reproduction. Our results indicate that: (1) the opisthe's oral primordium develops de novo beneath the cortex; (2) the frontoventral and transverse cirral anlagen, cirrus I/1, and marginal anlagen in both dividers develop de novo separately; (3) the dorsal kinety anlagen, the three rightmost ones of which produce three caudal cirri for the proter, occur within the parental structures in the mid-body region; (4) the opisthe acquires two caudal cirri, one from the end of each two rightmost kineties; and (5) there are two macronuclei and one micronucleus in the doublet and they divide amitotically and mitotically, respectively. Finally, we speculate that this special differentiation may be an adaptive form to adverse environments.
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Affiliation(s)
- Jinyu Fu
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
| | - Yong Chi
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
| | - Xiaoteng Lu
- Department of Biology, Shenzhen MSU-BIT University, Shenzhen, 518172 China
| | - Feng Gao
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
| | - Saleh A. Al-Farraj
- Zoology Department, College of Science, King Saud University, Riyadh, 11451 Saudi Arabia
| | - Giulio Petroni
- Department of Biology, University of Pisa, 56126 Pisa, Italy
| | - Jiamei Jiang
- Engineering Research Center of Environmental DNA and Ecological Water Health Assessment, Shanghai Ocean University, Shanghai, 201306 China
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Wei F, Pan B, Diao J, Wang Y, Sheng Y, Gao S. The micronuclear histone H3 clipping in the unicellular eukaryote Tetrahymena thermophila. MARINE LIFE SCIENCE & TECHNOLOGY 2022; 4:584-594. [PMID: 37078088 PMCID: PMC10077241 DOI: 10.1007/s42995-022-00151-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 10/07/2022] [Indexed: 05/02/2023]
Abstract
Clipping of the histone H3 N-terminal tail has been implicated in multiple fundamental biological processes for a growing list of eukaryotes. H3 clipping, serving as an irreversible process to permanently remove some post-translational modifications (PTMs), may lead to noticeable changes in chromatin dynamics or gene expression. The eukaryotic model organism Tetrahymena thermophila is among the first few eukaryotes that exhibits H3 clipping activity, wherein the first six amino acids of H3 are cleaved off during vegetative growth. Clipping only occurs in the transcriptionally silent micronucleus of the binucleated T. thermophila, thus offering a unique opportunity to reveal the role of H3 clipping in epigenetic regulation. However, the physiological functions of the truncated H3 and its protease(s) for clipping remain elusive. Here, we review the major findings of H3 clipping in T. thermophila and highlight its association with histone modifications and cell cycle regulation. We also summarize the functions and mechanisms of H3 clipping in other eukaryotes, focusing on the high diversity in terms of protease families and cleavage sites. Finally, we predict several protease candidates in T. thermophila and provide insights for future studies. Supplementary Information The online version contains supplementary material available at 10.1007/s42995-022-00151-0.
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Affiliation(s)
- Fan Wei
- Institute of Evolution and 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
| | - Bo Pan
- Institute of Evolution and 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
| | - Jinghan Diao
- Institute of Evolution and 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
| | - Yuanyuan Wang
- Institute of Evolution and 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
| | - Yalan Sheng
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
| | - Shan Gao
- Institute of Evolution and 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
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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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Zhang T, Tang Q, Chen Z, Lian C, Yang X, Song W, Warren A, Shao C. Insights into the phylogeny of the family Deviatidae (Protozoa, Ciliophora, Hypotrichia) based on multi-gene, morphological and ontogenetic information, with the establishment of a new species Deviata multilineae n. sp. Mol Phylogenet Evol 2022; 177:107623. [PMID: 36058509 DOI: 10.1016/j.ympev.2022.107623] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 08/10/2022] [Accepted: 08/29/2022] [Indexed: 11/25/2022]
Abstract
Hitherto, the phylogeny of ciliated protists, an important group of model organisms in many fields, has been mainly based on a single marker gene (SSU rDNA, nuclear small subunit ribosomal RNA gene). However, there is increasing evidence showing this is insufficient to provide robust phylogenies and has resulted in confusing systematics in many ciliates groups. Among these, the phylogenies within family Deviatidae (Spirotrichea, Hypotrichia) are ambiguous due to the dependence on SSU rDNA and undersampling. Here, we provide eight new sequences and conduct phylogenetic analyses based on both multi-gene and single-gene to clarify evolutionary relationships among all deviatids for which gene sequence are available. The results reveal that: (1) the monophyly of Deviatidae is well-supported by both single-gene and concatenated data; (2) the presence of fine cirri and relatively wide spacing of these cirri within all rows are plesiomorphies of Deviatidae; (3) Pseudosincirra longicirrata is closely related to Deviata rositae, which is supported by their shared possession of dorsomarginal kineties; (4) phylogenetic analyses and approximately unbiased test based on multi-gene support a close relationship among taxa lacking dorsomarginal kineties (D. parabacilliformis, D. multilineae nov. spec., D. abbrevescens, D. brasiliensis and Perisincirra paucicirrata); (5) Deviatidae shows a close relationship with Dorsomarginalia and Strongylidium-Hemiamphisiella-Pseudouroleptus assemblage, suggesting the presence/absence of dorsomarginal kineties is phylogenetically informative in this family and presence of them may be a plesiomorphy. Based on the morphological, morphogenetic and phylogenetic data, the evolutionary relationships within Deviatidae are hypothesized, and a new ciliate, Deviata multilineae nov. spec., collected from China, is investigated.
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Affiliation(s)
- Tengteng Zhang
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi'an 710119, China
| | - Qiuyue Tang
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi'an 710119, China
| | - Zhuofan Chen
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi'an 710119, China
| | - Chunyu Lian
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi'an 710119, China
| | - Xiaoqing Yang
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi'an 710119, China
| | - Weibo Song
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi'an 710119, China; Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Alan Warren
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
| | - Chen Shao
- Laboratory of Protozoological Biodiversity and Evolution in Wetland, College of Life Sciences, Shaanxi Normal University, Xi'an 710119, China.
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Zhang X, Lu X, Chi Y, Jiang Y, Wang C, Al-Farraj SA, Vallesi A, Gao F. Timing and characteristics of nuclear events during conjugation and genomic exclusion in Paramecium multimicronucleatum. MARINE LIFE SCIENCE & TECHNOLOGY 2022; 4:317-328. [PMID: 37073165 PMCID: PMC10077201 DOI: 10.1007/s42995-022-00137-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 06/01/2022] [Indexed: 05/03/2023]
Abstract
Ciliated protists are ideal material for studying the origin and evolution of sex, because of their nuclear dimorphism (containing both germline micronucleus and somatic macronucleus in the same cytoplasm), special sexual processes (conjugation and autogamy), and high diversity of mating-type systems. However, the study of sexual process is limited to only a few species, due to the difficulties in inducing or observing conjugation. In the present study, we investigate the conjugation process in Paramecium multimicronucleatum: (1) of the three prezygotic divisions, all micronuclei undergo the first two divisions (meiosis I, II), while a variable number of nuclei undergo the third division (mitosis); (2) the synkaryon divides three times after fertilization, giving rise to eight products that differentiate into four macronuclear anlagen and four micronuclei; (3) cells restore the vegetative stage after two successive cell fissions during which the macronuclear anlagen are distributed into daughter cells without division, while micronuclei divide mitotically; (4) the parental macronucleus begins to fragment following the first meiotic division and finally degenerates completely; (5) the entire process takes about 110 h, of which about 85 h are required for macronuclear development. In addition, we describe for the first time the process of genomic exclusion occurring between amicronucleate and micronucleate cells of P. multimicronucleatum, during which the micronucleate cell contributes a pronucleus to the amicronucleate cell, resulting in both exconjugants being homozygotes. These results provide new insights into the diversity of sexual processes and lay an important cytological basis for future in-depth studies of mating systems in ciliates.
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Affiliation(s)
- Xue Zhang
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Key Laboratory of Mariculture (OUC), Ministry of Education, Qingdao, 266003 China
| | - Xiaoteng Lu
- Department of Biology, Shenzhen MSU-BIT University, Shenzhen, 518172 China
| | - Yong Chi
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Key Laboratory of Mariculture (OUC), Ministry of Education, Qingdao, 266003 China
| | - Yaohan Jiang
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Key Laboratory of Mariculture (OUC), Ministry of Education, Qingdao, 266003 China
| | - Chundi Wang
- Laboratory of Marine Protozoan Biodiversity and Evolution, Shandong University, Weihai, 264209 China
| | - Saleh A. Al-Farraj
- Zoology Department, College of Science, King Saud University, Riyadh, 11451 Saudi Arabia
| | - Adriana Vallesi
- Laboratory of Eukaryotic Microbiology and Animal Biology, University of Camerino, 62032 Camerino, Italy
| | - Feng Gao
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Key Laboratory of Mariculture (OUC), Ministry of Education, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, 266237 China
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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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