| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1986: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Mitochondria(mt) of Saccharomyces cerevisiae contain their inherent DNA(mtDNA), with which proteins constitute a superstructure, "mt-nucleoid", that change the conformation from the dispersd state to the integrated and vice versa under various growth conditions. In this study, we tried to elucidate mechanisms of these morphological changes regulated by mitochondrial(mt) or nuclear(nc) genes and control of nc-gene expression by a mt-gene.
1. Induction of mitochondrial-character mutants with different mutagens Haploid yeasts were treated with ethidium bromide(EB), laser, MnCl_2 and ultraviolet light(UV), then only EB and UV unduced respiratory-deficient mt- and nc-mutants, respectively. 2. Analysis of characters of the mutants
(1)Mutants for conformational changes of mt-nucleids
Mt-nucleoids in EB-induced rhoー mutant cells aggregated during growth phases. Some ncmutants produced normal cells at 25゜C and respiratory-deficient ones carrying aggregated nucleoids or no mtDNA at 36゜C. The other mutants consisted of cells containing the aggregated nucleoids or no nucleoid, irrespective of temperature.
(2)Effect of mt-gene on mating-type interconversion and sporulating ability
During spore germination and growth of homothallic strain FE-1, respiratory-deficient cells were formed at frequency of 10^<-3> and also were found to be mainly <alpha>-type haploids. On the other hand, protoplasts of <alpha>-type rho゜ YGU-20 regenerated respiration-positive a/<alpha> cells after fused with anuclear "miniprotoplasts" of YGU-4 carrying normal mitochondria.
3. Isolation, analyses and cloning of mtDNA and the application methods to protoplasts
Techniques for isolating mtDNA from mt-nuclioids or disrupted whole cells and for obtaining the electrophoresis profiles of the restriction fragments have been examined. However, no fragment of mtDNA was cloned yet. Works on devising methods for chemical or electric fusion of protoplasts are in progress.
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