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2. Separation of micronuclear DNA of Stylonychia lemnae by pulsed-field electrophoresis and identification of a DNA molecule with a high copy number.

Author

Maercker, C, Kortwig, H, and Lipps, H J

Abstract

DNA from the hypotrichous ciliatae Stylonychia lemnae was separated by PFGE. In addition to the separation of the macronuclear DNA molecules with a size up to approximately 40 kb, we were able to separate the micronuclear DNA with a size between approximately 90 kb and 2 Mb. One very prominent 90-kb DNA band appeared on the pulsed-field gels. We propose that this 90-kb DNA fragment represents a linear plasmid residing in the micronucleus in a very high copy number. About 10% of the micronuclear DNA consists of the 90-kb DNA molecule. It appears in the micronucleus as well as in the macronuclear anlagen during macronuclear development but not in the mature macronucleus. Thus, the multicopy DNA is eliminated during fragmentation of the macronuclear anlagen DNA in the course of macronuclear development. Therefore, this 90-kb DNA molecule might serve as an excellent tool to study the recognition and elimination of DNA during nuclear differentiation of hypotrichous ciliates.

Published
1999

3. A nuclear protein involved in apoptotic-like DNA degradation in Stylonychia: implications for similar mechanisms in differentiating and starved cells.

Author

Maercker C, Kortwig H, Nikiforov MA, Allis CD, and Lipps HJ

Subjects
Animals, Binding, Competitive, Blotting, Western, Cell Differentiation, Cell Nucleus genetics, Cell Nucleus metabolism, Chromosome Banding, Chromosomes genetics, Chromosomes metabolism, Ciliophora chemistry, Ciliophora cytology, Ciliophora immunology, Cross Reactions, In Situ Nick-End Labeling, Micronucleus, Germline genetics, Micronucleus, Germline metabolism, Molecular Weight, Nuclear Proteins chemistry, Nuclear Proteins immunology, Phosphoproteins chemistry, Phosphoproteins immunology, Protozoan Proteins chemistry, Protozoan Proteins immunology, Tetrahymena chemistry, Tetrahymena immunology, Ciliophora physiology, DNA Fragmentation, Nuclear Proteins metabolism, Phosphoproteins metabolism, Protozoan Proteins metabolism
Abstract

Ciliates are unicellular eukaryotic organisms containing two types of nuclei: macronuclei and micronuclei. After the sexual pathway takes place, a new macronucleus is formed from a zygote nucleus, whereas the old macronucleus is degraded and resorbed. In the course of macronuclear differentiation, polytene chromosomes are synthesized that become degraded again after some hours. Most of the DNA is eliminated, and the remaining DNA is fragmented into small DNA molecules that are amplified to a high copy number in the new macronucleus. The protein Pdd1p (programmed DNA degradation protein 1) from Tetrahymena has been shown to be present in macronuclear anlagen in the DNA degradation stage and also in the old macronuclei, which are resorbed during the formation of the new macronucleus. In this study the identification and localization of a Pdd1p homologous protein in Stylonychia (Spdd1p) is described. Spdd1p is localized in the precursor nuclei in the DNA elimination stage and in the old macronuclei during their degradation, but also in macronuclei and micronuclei of starved cells. In all of these nuclei, apoptotic-like DNA breakdown was detected. These data suggest that Spdd1p is a general factor involved in programmed DNA degradation in Stylonychia.

Published
1999
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