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Microorganisms Dec 2022Fertilization-initiated development and adult-onset aging are standard features in the life history of eukaryotes. In , the number of cell divisions after the birth of a...
Fertilization-initiated development and adult-onset aging are standard features in the life history of eukaryotes. In , the number of cell divisions after the birth of a new generation is an essential parameter of sexual phase transition and aging. However, the gene driving this process and its evolutionary origin have not yet been elucidated. Here we report several critical outcomes obtained by molecular genetics, immunofluorescence microscopy, transformation by microinjection, and enzymological analysis. The cloned immaturin gene induces sexual rejuvenation in both mature and senescent cells by microinjection. The immaturin gene originated from proteobacteria's glutathione-S-transferase (GST) gene. However, immaturin has been shown to lose GST activity and instead acquire nuclease activity. In vitro substrates for immaturin-nuclease are single- and double-stranded DNA, linear and circular DNA, and single-stranded viral genome RNA such as coronavirus. Anti-immaturin antibodies have shown that the subcellular localizations of immaturin are the macronucleus, cytoplasm, cell surface area, and cilia. The phase transition of sexuality is related to a decrease in the intracellular abundance of immaturin. We propose that sexual maturation and rejuvenation is a process programmed by the immaturin gene, and the sexual function of each age is defined by both the abundance and the intracellular localization mode of the immaturin-nuclease.
PubMed: 36677375
DOI: 10.3390/microorganisms11010082 -
Microorganisms Jan 2020Ciliates 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...
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 . Our results indicate that: (i) conjugation lasts for about 50 hours, the longest stage being the development of the new macronucleus (ca. 36 hours); (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 cells. When two amicronucleate cells mate, they separate after about 4 hours 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 cells.
PubMed: 31979289
DOI: 10.3390/microorganisms8020162 -
ELife Mar 2021Dynamins are targeted to specific cellular membranes that they remodel via membrane fusion or fission. The molecular basis of conferring specificity to dynamins for...
Dynamins are targeted to specific cellular membranes that they remodel via membrane fusion or fission. The molecular basis of conferring specificity to dynamins for their target membrane selection is not known. Here, we report a mechanism of nuclear membrane recruitment of Drp6, a dynamin member in . Recruitment of Drp6 depends on a domain that binds to cardiolipin (CL)-rich bilayers. Consistent with this, nuclear localization of Drp6 was inhibited either by depleting cellular CL or by substituting a single amino acid residue that abolished Drp6 interactions with CL. Inhibition of CL synthesis, or perturbation in Drp6 recruitment to nuclear membrane, caused defects in the formation of new macronuclei post-conjugation. Taken together, our results elucidate a molecular basis of target membrane selection by a nuclear dynamin and establish the importance of a defined membrane-binding domain and its target lipid in facilitating nuclear expansion.
Topics: Amino Acid Sequence; Cardiolipins; Dynamins; Nuclear Envelope; Protein Binding; Protozoan Proteins; Sequence Alignment; Tetrahymena thermophila
PubMed: 33661098
DOI: 10.7554/eLife.64416 -
Marine Life Science & Technology Aug 2023During a study on the diversity of ciliated protists in Lake Weishan Wetland, the largest wetland in northern China, four epibiotic sessilid peritrichs were isolated...
On four epibiotic peritrichous ciliates (Protozoa, Ciliophora) found in Lake Weishan Wetland: morphological and molecular data support the establishment of a new genus, gen. nov., and two new species.
During a study on the diversity of ciliated protists in Lake Weishan Wetland, the largest wetland in northern China, four epibiotic sessilid peritrichs were isolated from aquatic host animals. Two of them, i.e., Kellicott, 1885 and Fauré-Fremiet, 1943, were known species whereas the other two, i.e., gen. nov., sp. nov. and sp. nov., are new to science. The new genus gen. nov. is characterized by its branched non-contractile stalk, everted peristomial lip, obconical macronucleus and transverse silverlines. Two species are assigned to the new genus, namely sp. nov. and (Fauré-Fremiet, 1905) comb. nov. Morphologically, sp. nov. is recognized by its goblet-shaped zooids, single-layered peristomial lip, dichotomously branched stalk, and infundibular polykinety 3 (P3) containing three equal-length rows. sp. nov. is characterized by its slender zooid, curved macronucleus, and three equal-length rows in infundibular P3. Improved diagnoses and redescriptions of and are provided including, for the first time, data on the ciliature of . Phylogenetic analyses based on SSU rDNA, ITS1-5.8S rDNA -ITS2, and LSU rDNA sequence data strongly support the assertion that the family Epistylididae comprises morphospecies with different evolutionary lineages and indicate that gen. nov. may represent a new taxon at family level.
PubMed: 37637257
DOI: 10.1007/s42995-023-00184-z -
Microorganisms Feb 2023The conjusome plays an important role in the conjugation events that occur in . The conjusome appears in the anterior of conjugant pairs during the early stages of new...
The conjusome plays an important role in the conjugation events that occur in . The conjusome appears in the anterior of conjugant pairs during the early stages of new macronuclei (anlagen) development. It lacks a membrane, and is composed of a network of fibrous, electron dense material, containing background cytoplasm and ribosomes. Several proteins localize to this organelle, including Pdd1p, a chromodomain protein that participates in the formation of chromatin-containing structures in developing macronuclear anlagen, and is associated with the elimination of specific germ-line sequences from developing macronuclei. Conjugants lacking the allele in the parental macronucleus do not show Pdd1p antibody staining in conjusomes. Investigations were performed using mutant cell lines, uniparental cytogamy and drug treatment, and show that the conjusome appears to be dependent on parental macronuclei condensation, and is a transitory organelle that traffics nuclear determinants from the parental macronucleus to the developing anlagen. These data, taken together with Pdd1p knockout experiments, suggest the conjusome is involved in the epigenetic phenomena that occur during conjugation and sexual reorganization. This is likely a conserved organelle. Conjusome-like structures were also observed in another Ciliate, . In general, conjusomes have features that resemble germ line P-granules.
PubMed: 36838383
DOI: 10.3390/microorganisms11020418 -
Frontiers in Cell and Developmental... 2019In the ciliate , a 631-amino acid -MAPK1 protein kinase was found to localize in nucleoli of the transcriptionally active nucleus (macronucleus) and act as a key...
In the ciliate , a 631-amino acid -MAPK1 protein kinase was found to localize in nucleoli of the transcriptionally active nucleus (macronucleus) and act as a key component of an autocrine, cell-growth promoting self-signaling mechanism. While its 283-amino acid N-terminal domain includes all the structural specificities of the mitogen-activated protein kinases required for a catalytic function, the 348-amino acid C-terminal domain is structurally unique with undetermined functions. By expressing the two -MAPK1 domains tagged with the green fluorescent protein in mammalian fibroblasts, the yeast and the ciliate , evidence was obtained that the C-terminal domain contains all the sequence information responsible for the -MAPK1 subcellular localization. However, in fibroblasts and this information determined a nucleolar localization of the GFP-tagged C-terminal domain, and a ciliary localization in . In the light of these findings, the -MAPK1 localization in was re-examined via immunoreactions and shown to be ciliary besides that nuclear, as is the case for the mammalian intestinal cell kinase with which the -MAPK1 N-terminal domain shares a strong sequence identity and a catalytic function.
PubMed: 31681773
DOI: 10.3389/fcell.2019.00244 -
Microorganisms Feb 2023Locus-specific gene amplification and genome-wide endoreplication generate the elevated copy number of ribosomal DNA (rDNA, 9000 C) and non-rDNA (90 C) chromosomes in...
Locus-specific gene amplification and genome-wide endoreplication generate the elevated copy number of ribosomal DNA (rDNA, 9000 C) and non-rDNA (90 C) chromosomes in the developing macronucleus of . Subsequently, all macronuclear chromosomes replicate once per cell cycle during vegetative growth. Here, we describe an unanticipated, programmed switch in the regulation of replication initiation in the rDNA minichromosome. Early in development, the 21 kb rDNA minichromosome is preferentially amplified from 2 C to ~800 C from well-defined origins, concurrent with genome-wide endoreplication (2 C to 8-16 C) in starved mating (endoreplication (ER) Phase 1). Upon refeeding, rDNA and non-rDNA chromosomes achieve their final copy number through resumption of just the endoreplication program (ER Phase 2). Unconventional rDNA replication intermediates are generated primarily during ER phase 2, consistent with delocalized replication initiation and possible formation of persistent RNA-DNA hybrids. Origin usage and replication fork elongation are affected in non-rDNA chromosomes as well. Despite the developmentally programmed 10-fold reduction in the ubiquitous eukaryotic initiator, the Origin Recognition Complex (ORC), active initiation sites are more closely spaced in ER phases 1 and 2 compared to vegetative growing cells. We propose that initiation site selection is relaxed in endoreplicating macronuclear chromosomes and may be less dependent on ORC.
PubMed: 36838456
DOI: 10.3390/microorganisms11020491 -
Proceedings of the National Academy of... Jan 2023During their development following sexual conjugation, ciliates excise numerous internal eliminated sequences (IESs) from a copy of the germline genome to produce the...
During their development following sexual conjugation, ciliates excise numerous internal eliminated sequences (IESs) from a copy of the germline genome to produce the functional somatic genome. Most IESs are thought to have originated from transposons, but the presumed homology is often obscured by sequence decay. To obtain more representative perspectives on the nature of IESs and ciliate genome editing, we assembled 40,000 IESs of , a species belonging to a lineage (Heterotrichea) that diverged early from those of the intensively studied model ciliate species. About a quarter of IESs were short (<115 bp), largely nonrepetitive, and with a pronounced ~10 bp periodicity in length; the remainder were longer (up to 7 kbp) and nonperiodic and contained abundant interspersed repeats. Contrary to the expectation from current models, the assembled germline genome encodes few transposases. Instead, its most abundant repeat (8,000 copies) is a Miniature Inverted-repeat Transposable Element (MITE), apparently a deletion derivative of a germline-limited Pogo-family transposon. We hypothesize that MITEs are an important source of IESs whose proliferation is eventually self-limiting and that rather than defending the germline genomes against mobile elements, transposase domestication actually facilitates the accumulation of junk DNA.
Topics: Humans; Ciliophora; DNA Transposable Elements; DNA, Protozoan; Gene Editing; Germ Cells; Transposases
PubMed: 36669106
DOI: 10.1073/pnas.2213985120 -
BMC Microbiology Dec 2020The taxonomy of tintinnine ciliates is vastly unresolved because it has traditionally been based on the lorica (a secreted shell) and it has only recently incorporated...
Three redescriptions in Tintinnopsis (Protista: Ciliophora: Tintinnina) from coastal waters of China, with cytology and phylogenetic analyses based on ribosomal RNA genes.
BACKGROUND
The taxonomy of tintinnine ciliates is vastly unresolved because it has traditionally been based on the lorica (a secreted shell) and it has only recently incorporated cytological and molecular information. Tintinnopsis, the most speciose tintinnine genus, is also the most problematic: it is known to be non-monophyletic, but it cannot be revised until more of its species are studied with modern methods.
RESULTS
Here, T. hemispiralis Yin, 1956, T. kiaochowensis Yin, 1956, and T. uruguayensis Balech, 1948, from coastal waters of China, were studied. Lorica and cell features were morphometrically investigated in living and protargol-stained specimens, and sequences of three ribosomal RNA (rRNA) loci were phylogenetically analyzed. The three species show a complex ciliary pattern (with ventral, dorsal, and posterior kineties and right, left, and lateral ciliary fields), but differ in lorica morphology, details of the somatic ciliature and rRNA gene sequences. Tintinnopsis hemispiralis is further distinguished by a ciliary tuft (a ribbon of very long cilia originated from the middle portion of the ventral kinety and extending out of the lorica) and multiple macronuclear nodules. Both T. kiaochowensis and T. uruguayensis have two macronuclear nodules, but differ in the number of somatic kineties and the position of the posterior kinety. Two neotypes are fixed for T. hemispiralis and T. kiaochowensis to stabilize the species names objectively, mainly because of the previous unavailability of type materials. By phylogenetic analysis and comparison with closely-related species, we infer that the ciliary tuft and details such as the commencement of the rightmost kinety in the lateral ciliary field are synapomorphies that may help clarify the systematics of Tintinnopsis-like taxa.
CONCLUSION
The redescriptions of three poorly known Tintinnopsis species, namely T. hemispiralis, T. kiaochowensis, and T. uruguayensis firstly revealed their ciliary patterns and rRNA sequences. This study expands knowledge and database of tintinnines and helps in identifying potential synapomorphies for future taxonomic rearrangements.
Topics: China; Cilia; Ciliophora; DNA, Protozoan; Genes, rRNA; Macronucleus; Phylogeny; RNA, Ribosomal; Seawater; Species Specificity
PubMed: 33317450
DOI: 10.1186/s12866-020-02057-2 -
Zoological Research Sep 2022During faunal studies of psammophilic ciliates along the coast of Qingdao, China, several marine karyorelictean species were isolated. Among them, four species within...
During faunal studies of psammophilic ciliates along the coast of Qingdao, China, several marine karyorelictean species were isolated. Among them, four species within the genus were investigated, including two species new to science: i.e., , , , and has been reported several times, but this study is the first to provide detailed morphological characters and phylogenetics. can be distinguished from its congeners by the presence of complex cortical granules, fewer macronuclei, and longer body size. differs from its congeners by having 14-17 right lateral ciliary rows and 24-37 dikinetids of intrabuccal kinety. Poorly known var. (Kahl, 1933) Foissner, 1996 should be elevated from subspecies to species level, (Foissner, 1996) , based on detailed redescriptions with statistical data, living morphology, infraciliature, and species definitions. Small subunit (SSU) rDNA was sequenced for the four species, and phylogenetic analysis revealed that all known taxa in formed the outline branch to the genus with moderate to high bootstrap support among lineages.
Topics: Animals; China; Ciliophora; DNA, Ribosomal; Phylogeny
PubMed: 35993134
DOI: 10.24272/j.issn.2095-8137.2022.014