Morphology and development of the macronuclei of the ciliates Stylonychia mytilus and Euplotes aediculatus

Ammermann, Dieter

doi:10.1007/bf00285634

Cited by 168 publications

(58 citation statements)

References 23 publications

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“…In these nuclei, which can be recognized both by the large size of their chromocenters and by the diploid number of polytene chromosomes, the chromosome number does not appear to be reduced as in polytene-type nuclei. Another peculiar giant chromosome type, which likewise does not present somatic pairing, has been found in some ciliates (e.g., Stylonychia mytilus) that have a macronucleus with polytene chromosomes and a diploid micronucleus (Ammermann, 1971;Ammermann et al, 1974). The polytenics of these ciliates display band and interband patterns (also seen in Drosophila), but the macronucleus disintegrates after its development while the micronucleus remains active.…”

Section: Plant Polytene Chromosomesmentioning

confidence: 93%

Plant polytene chromosomes

Carvalheira

2000

Genet. Mol. Biol.

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Section: Plant Polytene Chromosomesmentioning

confidence: 93%

Plant polytene chromosomes

Carvalheira

2000

Genet. Mol. Biol.

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“…Cell cultivation and isolation of macronuclear DNA and RNA Cells of S. lemnae strain DO (collected in North Germany; origin of the cloned α2-, ßr, ß2-tubulin genes), strain SP (South Germany; origin of the α 1-tubulin gene, pob and p4A3) and 6-Schi (South Germany; origin of pmal) were cultivated in Pringsheim solution as described by Ammermann [1] and DNA was purified from isolated macronuclei [2] as previously de scribed [48]. Total RNA was isolated by the procedure of Glisin [12] and contaminating DNA was eliminated by DNAse I digestion with 3000 units/ml at 37°C for 40 min.…”

Section: Methodsmentioning

confidence: 99%

“…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%

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

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“…These DNA pieces are produced by fragmentation of polytene chromosomes in postconjugative cells (12,13), and the process of macronuclear development from micronuclei results in considerable reduction in DNA sequence complexity (14). As was shown by Lawn and coworkers (15), macronuclear DNA is heterodisperse, but a particular DNA sequence in the macronucleus is found in a single size class of DNA molecules or in a small variety of discrete sizes.…”

mentioning

confidence: 99%

Macronuclear DNA of the hypotrichous ciliate Oxytricha fallax

Rae

Spear

1978

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

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DNA in the macronuclei of Oxytricha fallax, as in other hypotrichous ciliate protozoa, exists as small, achromosomal molecules rather than in chromosomes. We report studies on 0. fallax DNA using physicochemical procedures and nucleic acid hybridization. Macronuclear DNA molecules range in size from 22 kilobase pairs (kb) to about 0.5 kb. The DNA has a buoyant density in CsCl of 1.694 gcm-3 and a melting temperature in 15 mM NaCl/1.5 mM sodium citrate, pH 7, at 65.40. These values correspond to 34.7% Gua + Cyt and 28.1% Gua + Cyt, respectively, and base composition determined by thin-layer chromatography of nucleotides is 32.4% Gua + Cyt. The only modified nucleotide that is detectable is N6-methyldeoxyadenylate (0.2%), and the amount and kind of modification cannot account for the discrepancies in nucleotide composition determination by the three methods. The (rDNA) in the oocytes of amphibia (1, 2) and some insects (3, 4) and in the ciliate protozoa Tetrahymena (5, 6) and Paramecium (7). rDNA is also extrachromosomal in Physarum (8) and Dictyostelium (9). In Tetrahymena macronuclei (10) and in Physarum, rDNA is in the form of palindromic dimers. In Paramecium and other organisms, amplified genes for rRNA are tandemly repeated several to many times in extrachromosomal DNA molecules.Hypotrichous ciliate protozoa such as Oxytricha have a macronuclear genome comprised entirely of "extrachromosomal" or "achromosomal" DNA (11). These DNA pieces are produced by fragmentation of polytene chromosomes in postconjugative cells (12,13), and the process of macronuclear development from micronuclei results in considerable reduction in DNA sequence complexity (14). As was shown by Lawn and coworkers (15), macronuclear DNA is heterodisperse, but a particular DNA sequence in the macronucleus is found in a single size class of DNA molecules or in a small variety of discrete sizes.In this report, characteristics of the achromosomal macronuclear DNA of Oxytricha fallax are presented. 0. fallax is related to the unidentified species studied in Prescott's laboratory (15), but it is distinguished from the latter by its smaller size, by a different DNA buoyant density in CsCl, and by having two micronuclei per cell instead of four. Nevertheless, the processes of conjugation, macronuclear development, and vegetative reproduction in 0. fallax follow the general pattern described for other hypotrichs. Our reported studies on 0. fallax have concentrated on the genes for 25S and 19S rRNAs and for 5S rRNA. These genes have been localized to relatively small, nonpalindromic DNA, little larger than necessary to accomodate single coding sequences.MATERIALS AND METHODS Culture and In Vivo Labeling of 0. fallax. Cultures of 0. fallax were obtained from the Indiana University collection. Cells were grown in 0.1% Cerophyl medium with Chlamydonas reinhardtii as a food source. Medium was supplemented either with heat-killed Escherichia coli or with killed Klebsiella aerogenes in a vitamin/stigmasterol mixture (16). Cultures were harves...

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Morphology and development of the macronuclei of the ciliates Stylonychia mytilus and Euplotes aediculatus

Cited by 168 publications

References 23 publications

Plant polytene chromosomes

Plant polytene chromosomes

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

Macronuclear DNA of the hypotrichous ciliate Oxytricha fallax

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