Differential organization of mitochondrial genes in rice with normal and male-sterile cytoplasms.

Abstract

Southern blot analysis was used to identify differences in the characteristics of mitochondrial DNAs (mtDNAs) of rice with normal and male-sterile cytoplasms. Six oligonucleotides, coding for parts of plant mitochondrial proteins, were chemically synthesized and used as hybridization probes. In the restriction enzyme digested mtDNAS from normal and cms-Bo male-sterile cytoplasms, signals homologous to a probe for an apocylochrome b (cob) or an ATPase subunit 6 (atp6) gene were different in electrophoretic mobility between the two cytoplasms. Furthermore, the copy number of the two genes were considered to be twice as many in the mtDNAs of cms-Bo cytoplasm than that of normal cytoplasm. In four other DNA probes for a cytochrome oxidase subunit II, a cytochrome oxidase subunit I, a F1-ATPase a subunit, and an ATPase subunit 9 gene, no differential gene organization was observed between the two cytoplasms. Restriction fragment length polymorphisms in the probes for the cob and apt6 genes were observed among mtDNAs from six strains of cyioplasmically male-sterile rice. These results indicate a genetic divergence of rice mtDNA, and suggest that the gene rearrangements around tbe cob and atp6 genes of mtDNA, together with the duplication of the two genes, were brought about in some of the male-sterile cytoplasms during the domestication of rice.