Macronuclear development in Euplotes woodruffi following conjugation

Rao, M. V. Narasimha

doi:10.1016/0014-4827(68)90190-0

Cited by 39 publications

(22 citation statements)

References 3 publications

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“…[22]. Metabolic labeling and autoradiographic studies have led to the same conclusion for Tetrahymena thermophila [35, 501. Similar studies on the old macronucleus in numerous ciliate species (reviewed in [40]), including Euplotes woodrufi [41], indicate that it is also transcriptionally active during conjugation. Indeed, transcription can continue in the old macronucleus following its fragmentation during the conjugation process [6, 411. The sequencing analyses on the micronuclear, macronuclear, and cDNA clones of conm7 provide a clear indication of the nuclear origin of transcripts for this particular gene.…”

Section: Nuclear Origin Of Conjugation-specific Gene Transcriptssupporting

confidence: 62%

Conjugation‐Specific Genes in the Ciliate Euplotes crassus: Gene Expression from the Old Macronucleus

Zhong¹,

Ghosh²,

Jacobs³

et al. 1997

J Eukaryotic Microbiology

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Following mating or conjugation, the hypotrichous ciliate Euplotes crassus undergoes a massive genome reorganization process. While the nature of the rearrangement events has been well studied, little is known concerning proteins that carry out such processes. As a means of identifying such proteins, differential screening of a developmental cDNA library, as well as construction of a cDNA subtraction library, was used to isolate genes expressed only during sexual reproduction. Five different conjugation-specific genes have been identified that are maximally expressed early in conjugation, during the period of micronuclear meiosis, which is just prior to macronuclear development and the DNA rearrangement process. All five genes are retained in the mature macronucleus. Micronuclear, macronuclear, and cDNA clones of one gene (conZA7) have been sequenced, and the results indicate that the gene encodes a putative DNA binding protein. In addition, the presence of an internal eliminated sequence in the micronuclear copy of the conZA7 gene indicates that this conjugation-specific gene is transcribed from the old macronucleus.

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Section: Nuclear Origin Of Conjugation-specific Gene Transcriptssupporting

confidence: 62%

Conjugation‐Specific Genes in the Ciliate Euplotes crassus: Gene Expression from the Old Macronucleus

Zhong¹,

Ghosh²,

Jacobs³

et al. 1997

J Eukaryotic Microbiology

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“…During the last stage of anlagen development, the newly generated macronuclear DNA molecules are subject to multiple closely spaced rounds of DNA replication over a period of 10 to 15 h (30,36). To ensure that the same origins are used throughout this time period, we next analyzed the replication intermediates from cells isolated 105 and 115 h after mating.…”

Section: Resultsmentioning

confidence: 99%

Origin Usage during Euplotes Ribosomal DNA Amplification

2003

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The macronuclear genome of the ciliate Euplotes is comprised of millions of small linear DNA molecules that have telomeres on each end. These molecules are generated during the sexual stage of the life cycle, when the new macronucleus is formed by a series of DNA processing events and multiple rounds of DNA amplification. We have used two-dimensional gels to compare the location of the replication origins used during vegetative growth and the two periods during macronuclear development when DNA amplification takes place. When we examined the pattern of ribosomal DNA (rDNA) replication intermediates, we observed almost identical Y arcs regardless of when in the Euplotes life cycle the DNA was isolated. No bubble or bubble-to-Y arcs could be detected. This indicates that replication of the macronuclear rDNA initiates at or near the telomere even when these molecules are being differentially amplified. Since replication rarely initiated from both ends of the rDNA, we examined the direction of replication fork movement to determine which end of the rDNA served as the origin. Fork movement gels indicated that replication initiated at the 5 end. As transcription also starts near the telomere at the 5 end, our findings suggest that the telomere and the promoter region cooperate to recruit Euplotes replication initiation complexes.

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“…Synaptonemal complexes have been reported to array at the periphery of the micronucleus, e.g. in Euplotes woodrufi [41] and Trachelonemu sulcata [19]. In contrast to that, the synaptonemata are clearly distributed evenly throughout the nucleus in H. vermiculare.…”

Section: Discussionmentioning

confidence: 99%

The Nuclear Apparatus of the Ditransversal Ciliate Homalozoon Vermiculare (Ciliophora, Rhabdophora) During Interphase and Division Ii. the Micronuclei and Some Observations On Conjugation

Leipe

Hausmann

1993

J Eukaryotic Microbiology

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ABSTRACT. The nuclear apparatus of H. vermiculare consists of a single moniliform macronucleus and about 25 micronuclei. the micronuclei are about 3 μm in diameter and characterized by a meshwork of thick condensed chromatin. Mitosis is intranuclear and acentric as in all other ciliates. In metaphase, interpolar and chromosomal microtubules are abundant and the length of the micronuclei increases to about 5 μm. In late anaphase, interzonal microtubules become prominent and the spindle elongates to about 50 μ. In meta‐ and anaphase, the microtubules of the spindle are attached to the polar vesicles, and in anaphase, chromosomes become attached to it. In contrast to most other eukaryotes, micronuclear mitosis is not strictly bound to cell division in H. vermiculare. While most of the micronuclei divide prior to cytokinesis, others retain their interphasic shape or degenerate. In addition, some micronuclei divide in the interdivision period, i.e. between two successive divisions of the cell and macronucleus. Mating cells of H. vermiculare become joined to each other in the cilia‐free region covering the cytostome. In the course of conjugation, the cell membranes and the underlying oral filamentous sheaths of both cells fuse, thus uniting the endoplasm of both cells in the mouth region. Synaptonemal complexes in the meiotic chromosomes are more distinct in H. vermiculare than in most other dilates. the micrographs presented here depict dearly the central filament, transverse elements, and other substructures.

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Macronuclear development in Euplotes woodruffi following conjugation

Cited by 39 publications

References 3 publications

Conjugation‐Specific Genes in the Ciliate Euplotes crassus: Gene Expression from the Old Macronucleus

Conjugation‐Specific Genes in the Ciliate Euplotes crassus: Gene Expression from the Old Macronucleus

Origin Usage during Euplotes Ribosomal DNA Amplification

The Nuclear Apparatus of the Ditransversal Ciliate Homalozoon Vermiculare (Ciliophora, Rhabdophora) During Interphase and Division Ii. the Micronuclei and Some Observations On Conjugation

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