42. Comparative analysis of mitchondrial total proteins in cytoplasmic male- sterility systems of rice

Institute of Genetics, Department of Bioengineering, Fudan University, Shanghai, China

The mitochondrial DNA (mt-DNA) translation products of isolated mitochondria from the cytoplasmic male-sterile plants of maize and sorghum have been studied by Forde et al. (1978), Forde and Leaver (1980a,b), and Dixon and Leaver (1982). Some differences between the male-sterile and the maintainer lines were noted in this regard. It was suggested that the cytoplasmic male- sterility gene may be located in the mitochondrial genome. About the male- sterility systems of rice, however, nothing has been known.

We have investigated the mt-DNA translation products and the protein system in purified mitochondria isolated from the WA-type cytoplasmic male-sterile line and its maintainer line. Mitochondria were isolated and purified from etiolated seedlings. They were lysed by SDS and then analyzed by SDS- polyacrylamide gel electrophoresis. More than 30 bands of the total mt- proteins were clearly observed.

Two additional bands, 63KD and 59KD, respectively, were found in the male- sterile line, but they were absent in the maintainer line. In view of their heavy contents, they may be structural proteins.

In order to localize these additional mt-proteins, purification of mitochondrial inner membranes and electrophoretic comparison of the difference in protein fractions between the male-sterile and maintainer lines have also been made. The inner membrane protein fractions from the male-sterile line were higher than those from the maintainer line.

These experimental results agree with the findings in maize and sorghum. It may also be the case with rice that the cytoplasmic male-sterility gene is involved in the mitochondrial genome.

Dixon, L.K. and C.J. Leaver, 1982. Mitochondrial gene expression and cytoplasmic male sterility in sorghum. Plant Mol. Biol. 1:89-102.

Forde, B.G. and C.J. Leaver, 1980a. Nuclear and cytoplasmic genes controlling synthesis of variant mitochondrial polypeptides in male sterile maize. Proc. Nat. Acad. Sci. USA 77: 418-422.

Forde, B.G. and C.J. Leaver, 1980b. Mitochondrial genome expression in maize: Possible involvement of variant mitochondrial polypeptides in cytoplasmic male sterility. In D.R. Davies and D.A. Hopwood (eds), The Plant Genome, pp. 131- 146. John Innes Charity, Norwich, England.

Forde, B.G., R.J.C. Oliver and C.J. Leaver, 1978. Variation in mitochondrial translation products associatd with male sterile cytoplasms in maize. Proc. Nat. Acad. Sci. USA 75: 3841-3845.

Leaver, C.J. and B.G. Forde, 1980. Mitochondrial genome expression in higher plants. In C.J. Leaver (ed.), Genome Organization and Expression in Plants, pp. 407-425. N.Y. Plenum Press, New York.