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A possible role of mitochondria in the apoptotic‐like programmed nuclear death of Tetrahymena thermophila
Author(s) -
Kobayashi Takashi,
Endoh Hiroshi
Publication year - 2005
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2005.04936.x
Subject(s) - macronucleus , tetrahymena , biology , dna laddering , microbiology and biotechnology , nuclear dna , mitochondrion , autophagosome , endonuclease , programmed cell death , apoptosis , paramecium aurelia , cell nucleus , chromatin , mitochondrial dna , dna fragmentation , dna , biochemistry , nucleus , autophagy , paramecium , gene
The ciliated protozoan Tetrahymena has a unique apoptosis‐like process, which is called programmed nuclear death (PND). During conjugation, the new germinal micro‐ and somatic macro‐nuclei differentiate from a zygotic fertilized nucleus, whereas the old parental macronucleus degenerates, ensuring that only the new macronucleus is responsible for expression of the progeny genotype. As is the case with apoptosis, this process encompasses chromatin cleavage into high‐molecular mass DNA, oligonucleosomal DNA laddering, and complete degradation of the nuclear DNA, with the ultimate outcome of nuclear resorption. Caspase‐8‐ and caspase‐9‐like activities are involved in the final resorption process of PND. In this report, we show evidence for mitochondrial association with PND. Mitochondria and the degenerating macronucleus were colocalized in autophagosome using two dyes for the detection of mitochondria. In addition, an endonuclease with similarities to mammalian endonuclease G was detected in the isolated mitochondria. When the macronuclei were incubated with isolated mitochondria in a cell‐free system, DNA fragments of 150–400 bp were generated, but no DNA ladder appeared. Taking account of the present observations and the timing of autophagosome formation, we conclude that mitochondria might be involved in Tetrahymena PND, probably with the process of oligonucleosomal laddering.