EFFECTS OF MITOCHONDRIA ON ELECTROFUSION OF YEAST PROTOPLASTS

The effect of mitochondria on membrane fusion of yeast protoplasts was investigated in order to regulate electrofusion procedures for yeast breeding. We have found that the cell membrane fusion behavior of resp iration-deficient yeasts (rho(-)) was remarkably different from that o f normal yeasts (rho(+)). Induction of cell membrane fusion in rho(+) protoplasts appeared under the pulse condition (height: 2.5-5.5 kV cm( -1) and duration: 25-430 mu s) after pearl chains were formed. In cell membrane fusants of rho(+) protoplasts, the time interval of morpholo gical change from the long to short slate was 3-11 s. On the other han d, induction of cell membrane fusion in rho(-) protoplasts appeared un der the higher pulse condition (height: 4.0-7.0 kV cm(-1) and duration : 20-500 mu s). The time interval of the morphological change from the long to short stale was 110-170 s ill cell membrane fusants of rho(-) protoplasts. The zeta-potential of rho(+) protoplasts was -10-30 mV a nd that of the rho(-) protoplasts was -25-60 mV. The surface charge of the rho(-) protoplasts was more negative than that of rho(+) protopla sts; therefore, regulation of electrofusion electrofusion among variou s kinds of yeast strains was possible by changing the surface charge o f the protoplasts using mitochondrial mutations. (C) 1998 Elsevier Sci ence Inc.