The development of the macronucleus in the ciliated protozoan Stylonychia mytilus

Ammermann, Dieter; Steinbrück, Günther; L, von Berger; Hennig, Wolfgang

doi:10.1007/bf00283386

Cited by 303 publications

(146 citation statements)

References 18 publications

Supporting

Mentioning

141

Contrasting

Unclassified

Order By: Relevance

“…In another strain, T. pyriformis WH-6, no detectable satellites were found by Yao & Gorovsky (1974) and no marked differences between micro-and macronuclear DNA base composition was observed. In contrast, the DNA of the macronucleus of Stylonychia is quite homogeneous in CsCl gradients when compared to the DNA of the micronucleus (Prescott et al 1973;Ammermann et al 1974). S. coeruleus macronuclear DNA bands as a single, homogeneous component, showing no satellite bands.…”

Section: Discussion (I) Gc Contentmentioning

confidence: 86%

See 1 more Smart Citation

Macronuclear DNA in Stentor coeruleus: a first approach to its characterization

Pelvat

Haller

1976

Genet. Res.

View full text Add to dashboard Cite

SUMMARYThe macronuclei of Stentor coeruleus were isolated on a discontinuous sucrose gradient and their DNA was purified by conventional methods. The GC content was 32 mole %. The DNA banded as a single peak on analytical ultracentrifugation at 1-691 g/cm 3 . The molecular weight of the DNA was 5 x 10 6 to 4 x 10 7 daltons. Genome size determined by DNA-DNA reassociation kinetics was 6 x 10 10 daltons. The macronuclear genome was mostly simple, about 85 % being made of non-repetitive sequences.

show abstract

Section: Discussion (I) Gc Contentmentioning

confidence: 86%

“…Direct measurements on electron micrographs shows molecules of variable length. We unsuccessfully tried to discriminate classes of molecules based upon length, as Ammermann et al (1974) did for Stylonychia. However, length variation may be an artifact since shearing probably occurs for long molecules.…”

Section: Dna Characterization: Resultsmentioning

confidence: 99%

Macronuclear DNA in Stentor coeruleus: a first approach to its characterization

Pelvat

Haller

1976

Genet. Res.

View full text Add to dashboard Cite

show abstract

“…Ciliates contain two morphologically and functionally different nuclei: the generative micronuclei playing a major role in sexual reproduction (conjugation) and showing no or little transcriptional activity in the vegetative cell cycle, and the somatic macronuclei providing all RNA for vegetative cell growth [2,3]. Macronuclei develop from micronuclei by complex species specific processes, referred to as macronuclear development.…”

Section: Introductionmentioning

confidence: 99%

“…In the hypotrichous ciliate Stylonychia lemnae this macronuclear development includes chromosome polytenization, degradation of the giant chromosomes, selective DNA elimination, DNA rearrangement and DNA amplification [41]. The resulting transcriptionally active macronuclear genome is organized in about 15 000 different DNA molecules of 0.4 to 20 kbp in length, of which each is present in a distinct copy number of a few to more than 100 000 [3,10,18,19,30,48]. Each DNA molecule is thought to represent a transcription and replication unit and consists of a single intronless coding region flanked by short (74 bp to 1000 bp) AT-rich (75%-80%) noncoding sequences terminating in telomeric inverted repeats of C4A4.…”

Section: Introductionmentioning

confidence: 99%

Regulatory structures of gene expression, DNA-replication and DNA-rearrangement in macronuclear genes of Stylonychia lemnae, a hypotrichous ciliate

Helftenbein

Conzelmann

Becker

et al. 1989

European Journal of Protistology

View full text Add to dashboard Cite

“…Such an unconventional pathway predicts amplification of specific regions of the genome. At least, in Stylonichia [16] the high amplification of selected fractions of the unique sequences in the nuclear DNA is well established, while in Rhynchosciara [17], a low (2-4-fold) amplification of selected genes seems to occur prior to the transcription.…”

mentioning

confidence: 99%

DNA Synthesis in Circulating Erythroblasts of Anemic Duck

Modak

Commelin

Grosset

et al. 1975

European Journal of Biochemistry

View full text Add to dashboard Cite

In the circulating blood of anemic ducks, 5 % of all erythroid cells synthesize DNA. Immature erythroblasts, at all stages of differentiation, synthesize DNA although to a varying degree, while reticulocytes and erythrocytes do not. In the erythroid cell population labeled in vitro 2 h with 32Pi, half of the labeled DNA sediments as small-molecular-weight molecules, suggesting that these molecules fail to integrate into the high-molecular-weight components.Labeled DNA is found in the cytoplasmic postmitochondrial fractions and it is in a form of deoxyribonucleoproteins which cosediment with ribosomes as well as subribosomal particles in sucrose gradients. However, fixation with HCHO and centrifugation to equilibrium in CsCl gradient of these particles shows that the deoxyribonucleoprotein bands at the density different than the ribosomes and, thus, not physically linked to them. In EDTA-dissociated ribosomes, the deoxyribonucleoprotein particles cosediment with ribosomal subunits in such a way that the larger the particle, the larger the molecular weight of the DNA cosedimenting with it.The specific radioactivity of the cytoplasmic ribosome-derived and postribosomal-particlederived DNAs and the small molecular-weight nuclear DNA is similar and 10-20-fold higher than that of the bulk nuclear DNA. The former three DNA species sediment between 4-14 S. It is concluded that the cytoplasmic nonmitochondrial DNA species are of the nuclear origin. Less than 0.5 % of the total cellular nonmitochondrial DNA can be purified from the nucleus and the cytoplasm as fast-labeled small-molecular-weight components. All of the cellular nonmitochondrial DNA species band at the same mean buoyant density in Cs2S0,/urea gradients. All behave as native structures in hydroxyapatite and contain less than 5 "/, of their length as single-stranded regions. down product of the nuclear DNA. Furthermore, Fromson and Nemer [7] have attributed the presence of DNA in cytoplasmic nonmitochondrial fractions to contamination by a nuclear leakage. The problem, however, remains unsolved due to recent findings by Koch [8,9] that when compared to the nuclear DNA, the cytoplasmic DNA seems to be relatively enriched in unique sequences.The transfer of the products of transcription from the nucleus to the cytoplasm in the form of mRNA and its translation on ribosomes has been extensively investigated, for instance in avian erythroid cells [lo, 111. The primary transcription product of the globin genes is of the size 5 x lo6 daltons [12,13] and is suggested to be the precursor of the cytoplasmic mRNA (pre-mRNA). Although there is little doubt about the role of this pre-mRNA as intermediary in cellular information transfer, a straightforward scheme of direct

show abstract

The development of the macronucleus in the ciliated protozoan Stylonychia mytilus

Cited by 303 publications

References 18 publications

Macronuclear DNA in Stentor coeruleus: a first approach to its characterization

Macronuclear DNA in Stentor coeruleus: a first approach to its characterization

Regulatory structures of gene expression, DNA-replication and DNA-rearrangement in macronuclear genes of Stylonychia lemnae, a hypotrichous ciliate

DNA Synthesis in Circulating Erythroblasts of Anemic Duck

Contact Info

Product

Resources

About