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Masahiro Fujishima - One of the best experts on this subject based on the ideXlab platform.

  • draft genome sequences of three holospora species holospora obtusa holospora undulata and holospora elegans endonuclear symbiotic bacteria of the ciliate paramecium caudatum
    Fems Microbiology Letters, 2014
    Co-Authors: Hideo Dohra, Masahiro Fujishima, Tomohiro Suzuki, Kenya Tanaka, Haruo Suzuki
    Abstract:

    We present draft genome sequences of three Holospora species, hosted by the ciliate Paramecium caudatum ; that is, the macronucleus-specific H. obtusa and the Micronucleus-specific H. undulata and H. elegans . We investigate functions of orthologous core genes conserved across the three Holospora species, which may be essential for the infection and survival in the host nucleus.

  • Micronucleus specific bacterium holospora elegans irreversibly enhances stress gene expression of the host paramecium caudatum
    Journal of Eukaryotic Microbiology, 2008
    Co-Authors: Manabu Hori, Kimiko Fujii, Masahiro Fujishima
    Abstract:

    The bacterium Holospora is an endonuclear symbiont of the ciliate Paramecium. Previously, we reported that paramecia bearing the macronuclear-specific symbiont Holospora obtusa survived better than symbiont-free paramecia, even under high temperatures unsuitable for growth. The paramecia with symbionts expressed high levels of hsp70 mRNAs even at 25 degrees C, a usual growth temperature. We report herein that paramecia bearing the micronuclear-specific symbiont Holospora elegans also acquire the heat-shock resistance. Even after the removal of the bacteria from the hosts by treatment with penicillin, the resulting aposymbiotic paramecia nevertheless maintained their heat shock-resistant nature for over 1 yr. Like symbiotic paramecia, these aposymbiotic paramecia also expressed high levels of both hsp60 and hsp70 mRNAs even at 25 degrees C. Moreover, analysis by fluorescent in situ hybridization with a probe specific for Holospora 16S rRNA revealed that the 16S rRNA of H. elegans was expressed around the nucleoli of the macronucleus in the aposymbiotic cells. This result suggests the possible transfer of Holospora genomic DNA from the Micronucleus into the macronucleus in symbiotic paramecia. Perhaps this exogenous DNA could trigger the aposymbiotic paramecia to induce a stress response, inducing higher expression of Hsp60 and Hsp70, and thus conferring heat-shock resistance.

  • fates of the endonuclear symbiotic bacteria holospora obtusa and holospora undulata injected into the macronucleus of paramecium caudatum
    European Journal of Protistology, 2001
    Co-Authors: Ilya Skovorodkin, Masahiro Fujishima, Sergei I Fokin
    Abstract:

    Gram-negative endosymbiotic bacteria Holospora obtusa and H. undulata infect the macronucleus and Micronucleus of the ciliate Paramecium caudatum, respectively. Microsurgical transfers of infectious and reproductive forms of these symbionts were carried out from the donor nuclei to the macronucleus of aposymbiotic P. caudatum. The reproductive forms of the Micronucleus-specific H. undulata initially grew in the macronucleus, but were eventually eliminated from the nucleus within five days after the injection. On the other hand, the infectious forms of both Holospora species did not differentiate into the reproductive forms in the recipient macronucleus, and were expelled from the nucleus into the cytoplasm. These results indicate that the infectious form has no ability to differentiate into the reproductive form unless it infects the nucleus through the host digestive vacuole. It was found that injection of holosporas into the recipient macronucleus induced unusual vesicular structures in the nucleus.

Haruo Suzuki - One of the best experts on this subject based on the ideXlab platform.

Sergei I Fokin - One of the best experts on this subject based on the ideXlab platform.

  • Morphological features of P. chlorelligerum.
    2016
    Co-Authors: Olivia Lanzoni, Sergei I Fokin, Natalia Lebedeva, Alexandra Migunova, Giulio Petroni, Alexey Potekhin
    Abstract:

    (A) General view of living cell; (B) nuclear apparatus: macronucleus (Ma) and Micronucleus (black arrowhead) are indicated; (C) squashed cell: macronucleus (Ma) and Micronucleus (black arrowhead) are indicated; (D) pore of contractile vacuole (white arrowhead); (E) contractile vacuole with satellite vesicles; (F) cytoplasmic symbiotic algae released from the squashed ciliate cell; (G) tuft of long caudal cilia. Scale bars: 17 μm (A); 6 μm (B, C); 10 μm (D-F); 20 μm (G).

  • fates of the endonuclear symbiotic bacteria holospora obtusa and holospora undulata injected into the macronucleus of paramecium caudatum
    European Journal of Protistology, 2001
    Co-Authors: Ilya Skovorodkin, Masahiro Fujishima, Sergei I Fokin
    Abstract:

    Gram-negative endosymbiotic bacteria Holospora obtusa and H. undulata infect the macronucleus and Micronucleus of the ciliate Paramecium caudatum, respectively. Microsurgical transfers of infectious and reproductive forms of these symbionts were carried out from the donor nuclei to the macronucleus of aposymbiotic P. caudatum. The reproductive forms of the Micronucleus-specific H. undulata initially grew in the macronucleus, but were eventually eliminated from the nucleus within five days after the injection. On the other hand, the infectious forms of both Holospora species did not differentiate into the reproductive forms in the recipient macronucleus, and were expelled from the nucleus into the cytoplasm. These results indicate that the infectious form has no ability to differentiate into the reproductive form unless it infects the nucleus through the host digestive vacuole. It was found that injection of holosporas into the recipient macronucleus induced unusual vesicular structures in the nucleus.

  • experimental analysis of the resistance of paramecium caudatum ciliophora against infection by bacterium holospora undulata
    European Journal of Protistology, 1997
    Co-Authors: Sergei I Fokin, Ilya N Skovorodkin
    Abstract:

    Summary In some clones of Paramecium caudatum (to be referred to as “resistant”) infectious forms of Holospora undulata bacteria which are capable of infecting the Micronucleus were lysed within 3–4 h after invasion of the Micronucleus. After microsurgical transplantation of the Micronucleus of non-resistant into resistant paramecia (without removal of the recipient cell's Micronucleus), bacteria were lysed in both micronuclei of the heterokaryon cell. They were not lysed in either Micronucleus when the Micronucleus of a resistant cell was transplanted into a non-resistant one. After UV-microirradiation or microsurgical removal of the macronucleus from a resistant cell, lysis did not occur. The data suggest that the Micronucleus, as an independent morphological structure, cannot by itself initiate bacterial lysis. On the basis of these results it is clear that the process of H. undulata lysis in the Micronucleus of P. caudatum is mediated by the activity of the macronucleus.

Sol Katzman - One of the best experts on this subject based on the ideXlab platform.

  • 27 nt small RNAs are macronuclear in origin and do not require intron removal for their generation.
    2013
    Co-Authors: Alan M Zahler, Athena Lin, Zachary T. Neeb, Sol Katzman
    Abstract:

    A. Schematic diagram of internally eliminated sequence (IES) removal and macronuclear destined sequence (MDS) joining during macronuclear development. Pointer sequences are direct repeats found in the Micronucleus at MDS borders. Only one copy of the pointer is found in the macronucleus. B. Oxytricha trifallax Macronuclear Genome Browser screen shot of a region of the alpha telomere binding protein gene showing the junctions and overlapping pointer sequences of MDSs 9, 10 and 11. Only the mat24_06 library 26–28 nt small RNA track is shown. Note that the 26–28 nt small RNAs from the mat24_06 library from both strands overlap the MDS junction and pointer sequences. This is consistent with these small RNAs having originated from the mature parental macronucleus. C. Screen shot of a region of the alpha telomere binding protein gene containing its intron. 26–28 nt small RNAs from all seven mating libraries are shown. Note that sense strand small RNAs are found within the intron, indicating that they could be processed from introns. Also, small RNAs in the sense strand are found crossing the downstream intron/exon border, indicating that these are made from an RNA that did not undergo intron processing.

  • mating of the stichotrichous ciliate oxytricha trifallax induces production of a class of 27 nt small rnas derived from the parental macronucleus
    PLOS ONE, 2012
    Co-Authors: Alan M Zahler, Zachary Thomas Neeb, Athena Lin, Sol Katzman
    Abstract:

    Ciliated protozoans possess two types of nuclei; a transcriptionally silent Micronucleus, which serves as the germ line nucleus, and a transcriptionally active macronucleus, which serves as the somatic nucleus. The macronucleus is derived from a new diploid Micronucleus after mating, with epigenetic information contributed by the parental macronucleus serving to guide the formation of the new macronucleus. In the stichotrichous ciliate Oxytricha trifallax, the macronuclear DNA is highly processed to yield gene-sized nanochromosomes with telomeres at each end. Here we report that soon after mating of Oxytricha trifallax, abundant 27 nt small RNAs are produced that are not present prior to mating. We performed next generation sequencing of Oxytricha small RNAs from vegetative and mating cells. Using sequence comparisons between macronuclear and micronuclear versions of genes, we found that the 27 nt RNA class derives from the parental macronucleus, not the developing macronucleus. These small RNAs are produced equally from both strands of macronuclear nanochromosomes, but in a highly non-uniform distribution along the length of the nanochromosome, and with a particular depletion in the 30 nt telomere-proximal positions. This production of small RNAs from the parental macronucleus during macronuclear development stands in contrast to the mechanism of epigenetic control in the distantly related ciliate Tetrahymena. In that species, 28–29 nt scanRNAs are produced from the Micronucleus and these micronuclear-derived RNAs serve as epigenetic controllers of macronuclear development. Unlike the Tetrahymena scanRNAs, the Oxytricha macronuclear-derived 27 mers are not modified by 2′O-methylation at their 3′ ends. We propose models for the role of these “27macRNAs” in macronuclear development.

Martin A Gorovsky - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of a piwi-Related Gene Implicates Small RNAs in Genome Rearrangement in Tetrahymena
    Cell, 2002
    Co-Authors: Kazufumi Mochizuki, Noah A. Fine, Toshitaka Fujisawa, Martin A Gorovsky
    Abstract:

    During development of the somatic macronucleus from the germline Micronucleus in ciliates, chromosome rearrangements occur in which specific regions of DNA are eliminated and flanking regions are healed, either by religation or construction of telomeres. We identified a gene, TWI1, in Tetrahymena thermophila that is homologous to piwi and is required for DNA elimination. We also found that small RNAs were specifically expressed prior to chromosome rearrangement during conjugation. These RNAs were not observed in TWI1 knockout cells and required PDD1, another gene required for rearrangement, for expression. We propose that these small RNAs function to specify sequences to be eliminated by a mechanism similar to RNA-mediated gene silencing.

  • germline and somatic transformation of mating tetrahymena thermophila by particle bombardment
    Genetics, 1997
    Co-Authors: Donna Cassidyhanley, Josephine Bowen, Martin A Gorovsky, Eric S Cole, Lynn A Verplank, Jacek Gaertig, Peter J Bruns
    Abstract:

    Mating Tetrahymena thermophila were bombarded with ribosomal DNA-coated particles at various times in development. Both macronuclear and micronuclear transformants were recovered. Optimal developmental stages for transformation occurred during meiosis for the Micronucleus and during anlagen formation for the macronucleus. Evidence is given for transient retention of the introduced plasmid. Genetic and molecular tests confirmed that sexually heritable transformation was associated with integration at the homologous site in the recipient micronuclear chromosome.

  • germ line knockout heterokaryons of an essential α tubulin gene enable high frequency gene replacement and a test of gene transfer from somatic to germ line nuclei in tetrahymena thermophila
    Proceedings of the National Academy of Sciences of the United States of America, 1997
    Co-Authors: Martin A Gorovsky
    Abstract:

    The haploid Tetrahymena thermophila genome contains a single α-tubulin (ATU) gene. Using biolistic transformation, we disrupted one of the two copies of the ATU gene in the diploid germ-line Micronucleus. The heterozygous germ-line transformants were made homozygous in the Micronucleus by mating to a star strain containing a defective Micronucleus. This mating, known as round 1 genomic exclusion, resulted in two heterokaryon clones of different mating types which have both copies of the ATU gene knocked out in the Micronucleus but only wild-type genes in the polycopy somatic macronucleus. When these heterokaryons were mated, the exconjugant progeny cells did not grow because the new somatic macronuclei do not have any α-tubulin genes. However, when these conjugants were transformed with a functional marked ATU gene, viable transformants were obtained that contained the transforming ATU gene at the homologous locus in the new macronucleus. The exconjugant progeny could be rescued at a high efficiency (900 transformants per μg of DNA) with a wild-type ATU gene. Unlike previous macronuclear transformation protocols, this strategy should allow introduction of highly disadvantageous (but viable) mutations into Tetrahymena, providing a powerful tool for molecular and functional studies of essential genes. These knockout heterokaryons were used to demonstrate that gene transfer from somatic macronuclei to germ-line micronuclei occurs rarely if at all.

  • temporal and spatial association of histone h2a variant hv1 with transcriptionally competent chromatin during nuclear development in tetrahymena thermophila
    Genes & Development, 1993
    Co-Authors: Laurie A. Stargell, C A Dadd, Peter C Dedon, Mary C Davis, Richard G Cook, C D Allis, Josephine Bowen, Martin A Gorovsky
    Abstract:

    Vegetative cells of teh ciliated protozoan Tetrahymena thermophila contain a transcriptionally active macronucleus and a transcriptionally inactive Micronucleus. Although structurally and functionally dissimilar, these nuclei are products of a single postzygotic division during conjugationn, the sexual phase of the life cycle. Immunocytochemical analyses during growth, starvation, and conjugation were used to examine the nuclear deposition of hv1, a histone H2A variant that is found in macronuclei and though to play a role in transcriptionally active chromatin