山梨医科大学雑誌　第12巻1号　015-020(1997)

A Degradative Process Suggestive of Autophagic Death
in Post-Senescent Cells of Yeast Observed
by Light Microscopy

Mitsuyoshi MOTIZUKI, Zhaojun XU, and Kunio TSURUGI

Abstract: We previously reported that when virgin temperature-sensitive mutant edc28 cells of the yeast Saccharomyces cerevisiae were incubated at restrictive temperatures, they lost proliferative activity in 24 hr and thereafter cellular components became progressively degraded resulting in extensive fragmentation in 7 days in parallel with morphological changes suggestive of autophagocytosis. The process was named autophagic death. Here, to test whether yeast cells in the post-senescent life span undergo autophagic death, the edc28 cells were incubated at the permissive temperature and the cells that ceased the cell cycle during bud formation were observed by light microscopy for 7 days. Most cells that stopped the cell cycle produced an abnormally large bud. They accumulated vesicles within 24 hr after the arrest of the cell cycle and became shrunken and thin cytoplasm at day 7. A control strain without cdc mutation showed essentially the same morphological changes as the cdc28 senescent cells, suggesting that the biological process suggestive of autophagic death under light microscopy occurred in the post-senescence life span of the cells irrespective of cdc mutations.

Key words: Budding yeast, Autophagic death, Programmed cell death, postsenescent life span, cdc28 mutant




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