Fine Structure of Conjugation of the Ciliate Blepharisma japonicum II. Changes of Meiotic and Ameiotic Micronuclei and Development of Meiotic and Ameiotic Macronuclear Anlagen

Kovaleva, Valentina; Raikov, Igor B.; Miyake, Akio

doi:10.1016/s0003-9365(97)80015-2

Cited by 6 publications

(4 citation statements)

References 24 publications

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“…Briefly, high molecular weight DNA was isolated from the subcellular fractions of enriched MAC and MIC of B. stoltei strain ATCC 30299, separated using sucrose-gradient centrifugation ( 56 ). The MAC-enriched fraction was sequenced using PacBio HiFi reads and the MAC genome assembled with Flye (version 2.7-b1585) ( 19 ). The MIC-enriched fraction was sequenced with PacBio Continuous Long Reads (CLR) and analyzed using the BleTIES pipeline ( 57 ) to identify MIC-limited genomic regions.…”

Section: Methodsmentioning

confidence: 99%

“…Ciliates from Postciliodesmatophora are distantly related to these. Karyorelicts, as their name suggests, were formerly hypothesized to represent the “dawn” of ciliates, with “ancestral” nuclear features ( 16 – 18 ), in contrast to heterotrichs that exhibit “modern” nuclear features and development ( 16 , 19 , 20 ). Though the phylogenetic placement of heterotrichs and karyorelicts no longer supports such hypotheses ( 21 ), their nuclear and genomic development are still of much interest.…”

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confidence: 99%

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Origins of genome-editing excisases as illuminated by the somatic genome of the ciliate Blepharisma

Singh

Seah

Emmerich

et al. 2023

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

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Massive DNA excision occurs regularly in ciliates, ubiquitous microbial eukaryotes with somatic and germline nuclei in the same cell. Tens of thousands of internally eliminated sequences (IESs) scattered throughout the ciliate germline genome are deleted during the development of the streamlined somatic genome. The genus Blepharisma represents one of the two high-level ciliate clades (subphylum Postciliodesmatophora) and, unusually, has dual pathways of somatic nuclear and genome development. This makes it ideal for investigating the functioning and evolution of these processes. Here we report the somatic genome assembly of Blepharisma stoltei strain ATCC 30299 (41 Mbp), arranged as numerous telomere-capped minichromosomal isoforms. This genome encodes eight PiggyBac transposase homologs no longer harbored by transposons . All appear subject to purifying selection, but just one, the putative IES excisase, has a complete catalytic triad. We hypothesize that PiggyBac homologs were ancestral excisases that enabled the evolution of extensive natural genome editing.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

Origins of genome-editing excisases as illuminated by the somatic genome of the ciliate Blepharisma

Singh

Seah

Emmerich

et al. 2023

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

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“…The class Heterotrichea, the focus of this study, has been the subject of numerous morphological studies, yet few focus on the structure of their nuclei (e.g. Guttes and Guttes 1960, Ovchinnikova et al 1965, Kovaleva et al 1997a, Kovaleva et al 1997b).…”

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confidence: 99%

Nuclear Features of the Heterotrich Ciliate Blepharisma americanum: Genomic Amplification, Life Cycle, and Nuclear Inclusion

Wancura

Yan

Katz

et al. 2017

J Eukaryotic Microbiology

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Blepharisma americanum, a member of the understudied ciliate class Heterotrichea, has a moniliform somatic macronucleus that resembles beads on a string. Blepharisma americanum is distinguishable by its pink coloration derived from the autofluorescent pigment blepharismin and tends to have a single somatic macronucleus with 3–6 nodes and multiple germline micronuclei. We used fluorescence confocal microscopy to explore the DNA content and amplification between the somatic and germline nuclei of B. americanum through its life cycle. We estimate that the DNA content of the macronucleus and micronucleus are 43 ± 8 Gbp and 83 ± 16 Mbp respectively. This correlates with an approximate DNA content difference of 500‐fold from micronucleus to macronucleus and a macronuclear ploidy of ~1,100 N as compared to the presumably diploid micronucleus. We also investigate a previously reported macronuclear inclusion, which is present sporadically across all life cycle stages; this inclusion looks as if it contains blepharismin based on its fluorescent properties, but its function remains unknown. We also provide additional detail to our understanding of life cycles changes in B. americanum by analyses of fluorescent images. Overall, the data analyzed here contribute to our understanding of the diversity of nuclear architecture in ciliates by providing details on the highly polyploid somatic macronucleus of B. americanum.

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“…Stentor ; Lynn, 2008; Raikov, 1994; Shazib et al, 2014; Slabodnick et al, 2017; Terra, 1983). A recent experimental study by Wancura et al (2018) reported the ploidy level of macronuclei of the heterotrich ciliate, Blepharisma using fluorescent microscopy to be ~1027 N (Figure 4; Kovaleva et al, 1997; Miyake et al, 1991; Riley & Katz, 2001; Yan et al, 2016).…”

Section: Macronuclear Insights Across Ciliate Classesmentioning

confidence: 99%

Macronuclear development in ciliates, with a focus on nuclear architecture

Ahsan

Blanche

Katz

2022

J Eukaryotic Microbiology

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Ciliates are defined by the presence of dimorphic nuclei as they have both a somatic macronucleus and germline micronucleus within each individual cell. The size and structure of both germline micronuclei and somatic macronuclei vary tremendously among ciliates. Except just after conjugation (i.e. the nuclear exchange in their life cycle), the germline micronucleus is transcriptionally inactive and contains canonical chromosomes that will be inherited between generations. In contrast, the transcriptionally active macronucleus contains chromosomes that vary in size in different classes of ciliates, with some lineages having extensively fragmented gene‐sized somatic chromosomes while others contain longer multigene chromosomes. Here, we describe the variation in somatic macronuclear architecture in lineages sampled across the ciliate tree of life, specifically focusing on lineages with extensively fragmented chromosomes (e.g. the classes Phyllopharyngea and Spirotrichea). Further, we synthesize information from the literature on the development of ciliate macronuclei, focusing on changes in nuclear architecture throughout life cycles. These data highlight the tremendous diversity among ciliate nuclear cycles, extend our understanding of patterns of genome evolution, and provide insight into different germline and somatic nuclear features (e.g. nuclear structure and development) among eukaryotes.

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Fine Structure of Conjugation of the Ciliate Blepharisma japonicum II. Changes of Meiotic and Ameiotic Micronuclei and Development of Meiotic and Ameiotic Macronuclear Anlagen

Cited by 6 publications

References 24 publications

Origins of genome-editing excisases as illuminated by the somatic genome of the ciliate Blepharisma

Origins of genome-editing excisases as illuminated by the somatic genome of the ciliate Blepharisma

Nuclear Features of the Heterotrich Ciliate Blepharisma americanum: Genomic Amplification, Life Cycle, and Nuclear Inclusion

Macronuclear development in ciliates, with a focus on nuclear architecture

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