Abstract
Yeast spheroplasts were cultured in several sporulation media, each containing different kinds of inhibitors which affected meiosis, and the morphology of the mitochondrial nucleoids (mt-nucleoids) was examined using the DNA-binding fluorescent dye, 4′, 6-diamidino-2-phenylindole. Adding inhibitors which completely blocked meiosis and sporulation caused the mt-nucleoids to form two distinct morphological types. In the presence of actinomycin D, cycloheximide, methyl 2-benzimidazole carbamate and 2-(4-thiazolyl)-1H-benzimidazole, the mt-nucleoids fused with each other and showed a marked string-like appearance, as did the mt- nucleoids observed in normal sporulation process. In the presence of ethidium bromide, antimycin A, olygomycin, carbonyl cyanide m- chlorophenylhydrazone, mt-nucleoids appeared as fluorescent particles scattered in the cytoplasm. However, adding glucose to the sporulation medium containing antimycin A gave rise to a marked string-like appearance of mt-nucleoids in spite of strong inhibition of respiration. These results indicated that the morphology of mt-nucleoids was not directly associated with respiration itself, but that the preservation of complete mitochondrial DNAs and some metabolic activities related to respiration were required for the formation of string-like mt-nucleoids in sporulation media.
