Analysis and identification of anther-specific genes and male-sterility genes

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Exploiting the information on the genome sequences of rice and Arabidopsis, genes specifically expressed in anthers and those responsible for male sterility and fertility-restoration were analyzed using rice and Brassicaceae plants to develop novel techniques for F_1 hybrid breeding, which is presently the most reliable breeding method for improving plant productivity.Three genes controlling exine production were newly identified, and isolated from Arabidopsis. Since mutants having nonfunctional alleles of these genes produce pollen grains lacking germination ability, identification of these genes enables the production of male-sterile lines having high seed productivity in Brassicaceae crops. Using a Brassica oleracea line having a fertility-restorer gene for mur-CMS (cytoplasmic male sterility), which was selected in the present study, we found orf72 to be a candidate of the mitochondrial gene responsible for mur-CMS. We also isolated the fertility-restorer gene for Boro-CMS in rice, Rf1, first in the world, and revealed that Rf1 protein is transferred to mitochondria and interacts with mitochondrial mRNA. Fertility-restorer genes for two other types of CMS in rice were mapped on rice chromosomes, and regions harboring these genes were delimited into short parts of chromosomes. Identification of these genes will be achieved soon. In the study of mutant genes responsible for nuclear-genic male sterility, we developed a reverse genetic mutant-selection technique using Brassica petiole extract and an original, simple, efficient, and cost-effective technique for SNP analysis. These techniques are expected to contribute to the development of a novel F_1 hybrid breeding method.