Conjugation in Tetrahymena thermophila *1, *2A temporal analysis of cytological stages

Martindale, Duane W.; Allis, C. David; Bruns, Peter J.

doi:10.1016/0014-4827(82)90172-0

Cited by 195 publications

(158 citation statements)

References 22 publications

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“…Round I genomic exclusion (1,8,21) is a special type of abortive mating between WT and star (*) strains which have defective, hypodiploid MICs. Star strains can form pairs with WT but are not able to produce pronuclei during nuclear exchange and fertilization stages of conjugation (18,50,78). As a result, both partners of the pairs have only haploid MICs received from the WT cell, which are then endoreplicated to form homozygous diploid MICs in both cells.…”

Section: Methodsmentioning

confidence: 99%

Phosphorylation of the SQ H2A.X Motif Is Required for Proper Meiosis and Mitosis in Tetrahymena thermophila

Song

Gjoneska

Ren

et al. 2007

Molecular and Cellular Biology

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Phosphorylation of the C terminus SQ motif that defines H2A.X variants is required for efficient DNA double-strand break (DSB) repair in diverse organisms but has not been studied in ciliated protozoa. Tetrahymena H2A.X is one of two similarly expressed major H2As, thereby differing both from mammals, where H2A.X is a quantitatively minor component, and from Saccharomyces cerevisiae where it is the only type of major H2A. Tetrahymena H2A.X is phosphorylated in the SQ motif in both the mitotic micronucleus and the amitotic macronucleus in response to DSBs induced by chemical agents and in the micronucleus during prophase of meiosis, which occurs in the absence of a synaptonemal complex. H2A.X is phosphorylated when programmed DNA rearrangements occur in developing macronuclei, as for immunoglobulin gene rearrangements in mammals, but not during the DNA fragmentation that accompanies breakdown of the parental macronucleus during conjugation, correcting the previous interpretation that this process is apoptosis-like. Using strains containing a mutated (S134A) SQ motif, we demonstrate that phosphorylation of this motif is important for Tetrahymena cells to recover from exogenous DNA damage and is required for normal micronuclear meiosis and mitosis and, to a lesser extent, for normal amitotic macronuclear division; its absence, while not lethal, leads to the accumulation of DSBs in both micro-and macronuclei. These results demonstrate multiple roles of H2A.X phosphorylation in maintaining genomic integrity in different phases of the Tetrahymena life cycle.

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Section: Methodsmentioning

confidence: 99%

Phosphorylation of the SQ H2A.X Motif Is Required for Proper Meiosis and Mitosis in Tetrahymena thermophila

Song

Gjoneska

Ren

et al. 2007

Molecular and Cellular Biology

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“…Earlier studies have demonstrated that dramatic changes occur in the morphology of the pre-existing macronucleus during conjugation. The nucleus becomes a dense, balllike structure, migrates to the posterior of the cell, and over time becomes progressively smaller and completely disappears (Martindale et al, 1982;Cole and Soelter, 1997). Our study confirmed this wellknown behaviour of the pre-existing macronucleus during conjugation.…”

Section: Nuclear Events In Wt × Wt Are Synchronous Within a Conjugal mentioning

confidence: 99%

“…A transcriptionally-active macronucleus coexists with a transcriptionally-silent micronucleus, which is activated only at conjugation. The following description summarizes salient features of the conjugal process and is based on well-established reports (Martindale et al, 1982;Cole and Soelter, 1997). After establishment of a stable conjugal pair, the micronucleus elongates and becomes a long crescentlike structure during meiotic prophase.…”

Section: Introductionmentioning

confidence: 99%

MY01, a class XIV myosin, affects developmentally‐regulated elimination of the macronucleus during conjugation of Tetrahymena thermophila

Garcés

Hosein

Gavin

2009

Biology of the Cell

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Background information. Nuclear dimorphism is characteristic of ciliated protozoa. A transcriptionally-active macronucleus co-exists with a transcriptionally-silent micronucleus, which is activated only at conjugation. During conjugation, each conjugant develops two new genetically matched macronuclei and micronuclei, and the pre-existing macronucleus is eliminated. Elimination of the pre-existing macronucleus during conjugation is an apoptotic-like process. The macronucleus becomes highly condensed, DNA laddering occurs, caspase activity increases, acidic enzymes accumulate within the nucleoplasm, and the nucleus shrinks in size. The current study focused on the involvement of actin and myosin in nuclear events of conjugation. A myosin knockout strain was mated with wild-type, and the nuclear events were monitored with confocal microscopy.Results. Early nuclear events, including development of new macronuclei and micronuclei, appeared qualitatively normal in knockout conjugants. Completion of nuclear condensation and acidification in the pre-existing macronucleus was blocked in 44% of knockout conjugants. Knockout conjugants that failed to fully achieve nuclear condensation and acidification did not eliminate the pre-existing macronucleus. In control experiments, blockage of chromatin condensation, nuclear acidification, and macronuclear elimination was never observed in wild-type conjugants.Conclusions. Perturbation of either DNA fragmentation, chromatin condensation or nuclear acidification can lead to blockage of apoptotic-like elimination of the macronucleus in MYO1-knockout conjugants. Consistent with the known motor function of myosins and the involvement of Myo1 in vesicle trafficking in Tetrahymena, we argue that Myo1 could specifically affect condensation of chromatin and acidification of the nucleus through direct interaction with chromatin and through Myo1-dependent vesicle trafficking to the nucleus.

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“…22 When mixed together, cells of different mating types can conjugate under starvation conditions, which involves initiating synchronous meiosis of their MICs. 23 Meiosis has been well studied in T. thermophila in recent decades, thus providing a good model system for exploring the mechanism of ciliate meiosis initiation. [22][23][24][25][26][27] To determine whether Cdks are involved in meiosis initiation in ciliates, we screened T. thermophila for proteins containing the PSTAIRE-like cyclin-binding domain and identified Cdk3 (also named Tcdk3) as a candidate.…”

Section: Introductionmentioning

confidence: 99%

Cdk3, a conjugation-specific cyclin-dependent kinase, is essential for the initiation of meiosis in Tetrahymena thermophila

et al. 2016

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Meiosis is an important process in sexual reproduction. Meiosis initiation has been found to be highly diverse among species. In yeast, it has been established that cyclin-dependent kinases (Cdks) and cyclins are essential components in the meiosis initiation pathway. In this study, we identified 4 Cdks in the model ciliate, Tetrahymena thermophila, and we found one of them, Cdk3, which is specifically expressed during early conjugation, to be essential for meiosis initiation. Cdk3 deletion led to arrest at the pair formation stage of conjugation. We then confirmed that Cdk3 acts upstream of double-strand break (DSB) formation. Moreover, we detected that Cdk3 is necessary for the expression of many genes involved in early meiotic events. Through proteomic quantification of phosphorylation, co-expression analysis and RNA-Seq analyses, we identified a conjugation-specific cyclin, Cyc2, which most likely partners with Cdk3 to initiate meiosis.

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Conjugation in Tetrahymena thermophila 1, 2A temporal analysis of cytological stages

Cited by 195 publications

References 22 publications

Phosphorylation of the SQ H2A.X Motif Is Required for Proper Meiosis and Mitosis in Tetrahymena thermophila

Phosphorylation of the SQ H2A.X Motif Is Required for Proper Meiosis and Mitosis in Tetrahymena thermophila

MY01, a class XIV myosin, affects developmentally‐regulated elimination of the macronucleus during conjugation of Tetrahymena thermophila

Cdk3, a conjugation-specific cyclin-dependent kinase, is essential for the initiation of meiosis in Tetrahymena thermophila

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