Double paths of macronucleus differentiation at conjugation in Blepharisma japonicum

Miyake, Akio; Rivola, Valeria; Harumoto, Terue

doi:10.1016/s0932-4739(11)80340-8

Cited by 20 publications

(39 citation statements)

References 15 publications

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“…This alternative pathway of MAC development has also been observed experimentally after removal of primary macronuclear anlagen by microsurgery [9]. As conjugation progresses, the old (maternal) MACs are progressively degraded [9]. Since the B. stoltei MIC genome has numerous IESs which interrupt genes (Seah et al in prep.…”

Section: Introductionmentioning

confidence: 77%

Genome editing excisase origins illuminated by somatic genome of Blepharisma

Singh

Seah

Emmerich

et al. 2021

Preprint

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The germ-soma distinction is a defining feature of multicellular eukaryotes. Analogous to this, ciliates, a ubiquitous microbial eukaryote lineage, have morphologically and functionally distinct nuclei, but within single cells: the germline micronucleus (MIC) and somatic macronucleus (MAC). The origins and mechanisms of the MIC to MAC transformation, especially the extensive elimination of abundant internally eliminated sequences (IESs) and transposons during genome reorganization, are great biological mysteries. Blepharisma represents one of the two earliest diverging ciliate classes, and has unique, dual pathways of MAC development, making it ideal for investigating the functioning, origins and evolution of these processes. Here, we report the MAC genome assembly of Blepharisma stoltei strain ATCC 30299 (41 Mb), arranged as numerous alternative telomere-capped minichromosomes, tens to hundreds of kilobases long. The B. stoltei MAC genome encodes eight PiggyBac transposase homologs liberated from transposons. All are subject to purifying selection, but just one, the putative Blepharisma IES excisase, has a complete catalytic amino acid triad. Numerous genes encoding other domesticated transposases are present in B. stoltei, and often are comparably strongly upregulated in a similar timeframe to model ciliate genome reorganization homologs. Our phylogenetic investigations suggest the PiggyBac homologs may have been ancestral ciliate IES excisases. The B. stoltei MAC genome, together with the upcoming MIC genome, highlights the evolution and complex interplay between transposons, domesticated transposases, and genome reorganization in the context of germline-soma differentiation within single cells.

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Section: Introductionmentioning

confidence: 77%

Genome editing excisase origins illuminated by somatic genome of Blepharisma

Singh

Seah

Emmerich

et al. 2021

Preprint

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“…B. japonicum retained many primitive features such as the way of macronuclear division (10,11) and the nuclear changes in conjugation (12). It differs in this respect from E. raikovi and E. octocarinatus.…”

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confidence: 99%

Identification, characterization, and complete amino acid sequence of the conjugation-inducing glycoprotein (blepharmone) in the ciliate Blepharisma japonicum

Sugiura

Harumoto

2001

Proc. Natl. Acad. Sci. U.S.A.

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Conjugation in Blepharisma japonicum is induced by interaction between complementary mating-types I and II, which excrete blepharmone (gamone 1) and blepharismone (gamone 2), respectively. Gamone 1 transforms type II cells such that they can unite, and gamone 2 similarly transforms type I cells. Moreover, each gamone promotes the production of the other gamone. Gamone 2 has been identified as calcium-3-(2-formylamino-5-hydroxybenzoyl) lactate and has been synthesized chemically. Gamone 1 was isolated and characterized as a glycoprotein of 20 -30 kDa containing 175 amino acids and 6 sugars. However, the amino acid sequence and arrangement of sugars in this gamone are still unknown. To determine partial amino acid sequences of gamone 1, we established a method of isolation based on the finding that this glycoprotein can be concentrated by a Con A affinity column. Gamone 1 is extremely unstable and loses its biological activity once adsorbed to any of the columns that we tested. By using a Con A affinity column and native PAGE, we detected a 30-kDa protein corresponding to gamone 1 activity and determined the partial amino acid sequences of the four peptides. To isolate gamone 1 cDNA, we isolated mRNA from mating-type I cells stimulated by synthetic gamone 2 and then performed rapid amplification of cDNA ends procedures by using gene-specific primers and cloned cDNA of gamone 1. The cDNA sequence contains an ORF of 305 amino acids and codes a possibly novel protein. We also estimated the arrangement of sugars by comparing the affinity to various lectin columns.

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“…Although recent studies indicate that nucleus differentiation in ciliates requires biased assembly of the nuclear pore complex [55], the entire process has not yet been fully clarified. The most complicated nucleus differentiation was observed in the species Blepharisma japonicum in which macronucleus could differentiate through both sexual and asexual paths proceeded synchronously in each cell with one path eventually dominated the other [56]. Second, conjugation is performed under the control of the so-called "mating type systems", which exhibit significant variety in terms of mating type number, mating type determinants, and mating type inheritance [25].…”

Section: Discussionmentioning

confidence: 99%

Time-course analysis of nuclear events during conjugation in the marine ciliate Euplotes vannus and comparison with other ciliates (Protozoa, Ciliophora)

et al. 2019

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Ciliates represent a morphologically and genetically distinct group of single-celled eukaryotes that segregate germline and somatic functions into two types of nuclei and exhibit complex cytogenetic events during the sexual process of conjugation, which is under the control of the so-called "mating type systems". Studying conjugation in ciliates may provide insight into our understanding of the origins and evolution of sex and fertilization. In the present work, we studied in detail the sexual process of conjugation using the model species Euplotes vannus, and compared these nuclear events with those occurring in other ciliates. Our results indicate that in E. vannus: 1) conjugation requires about 75 hours to complete: the longest step is the development of the new macronucleus (ca. 64h), followed by the nuclear division of meiosis I (5h); the mitotic divisions usually take only 2h; 2) there are three prezygotic divisions (mitosis and meiosis I and II), and two of the eight resulting nuclei become pronuclei; 3) after the exchange and fusion of the pronuclei, two postzygotic divisions occur; two of the four products differentiate into the new micronucleus and macronucleus, respectively, and the parental macronucleus degenerates completely; 4) comparison of the nuclear events during conjugation in different ciliates reveals that there are generally three prezygotic divisions while the number of postzygotic divisions is highly variable. These results can serve as reference to investigate the mating type system operating in this species and to analyze genes involved in the different steps of the sexual process.

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Double paths of macronucleus differentiation at conjugation in Blepharisma japonicum

Cited by 20 publications

References 15 publications

Genome editing excisase origins illuminated by somatic genome of Blepharisma

Genome editing excisase origins illuminated by somatic genome of Blepharisma

Identification, characterization, and complete amino acid sequence of the conjugation-inducing glycoprotein (blepharmone) in the ciliate Blepharisma japonicum

Time-course analysis of nuclear events during conjugation in the marine ciliate Euplotes vannus and comparison with other ciliates (Protozoa, Ciliophora)

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