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Selection of the Germinal Micronucleus in Paramecium caudatum : Nuclear Division and Nuclear Death
Author(s) -
TAKA NORIKO,
KUROKAWA KOYA,
ARAKI TAKAKO,
MIKAMI KAZUYUKI
Publication year - 2006
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/j.1550-7408.2006.00091.x
Subject(s) - micronucleus test , biology , macronucleus , paramecium caudatum , micronucleus , paramecium , cell division , genetics , microbiology and biotechnology , ploidy , cytoplasm , cytokinesis , cell , gene , chemistry , toxicity , organic chemistry
. Each cell of Paramecium caudatum has a germinal micronucleus. When a bi‐micronucleate state was created artificially by micronuclear transplantation, both micronuclei divided for at least 2 cell cycles after nuclear transplantation. However, this bi‐micronucleate state was unstable and reduced to a uni‐micronucleate state after several fissions. Although the number of micronuclei was usually 1 during the vegetative phase, 4 presumptive micronuclei differentiated after conjugation. At the first post‐conjugational fission, only 1 of the 4 micronuclei divided, indicating that there is tight regulation of micronuclear number in exconjugants. Micronuclei that did not divide at the first post‐conjugational fission may persist through the first and second post‐conjugational cell cycles. The decision to divide appears to be separate from the decision to degenerate, as evidenced by division of a remaining micronucleus upon removal of the dividing micronucleus at the first division. Degeneration of micronuclei in exconjugants differs from that of haploid nuclei after meiosis. Nutritional state affected micronuclear degeneration. Under well‐fed conditions, the micronuclei destined to degenerate lost the ability to divide earlier than after starvation treatment, suggesting that micronuclear degeneration is an “apoptotic” phenomenon, probably under the control of the new macronuclei (macronuclear anlagen).