Mapping complementary genes in maize: positioning the rf1 and rf2 nuclear-fertility restorer loci of Texas (T) cytoplasm relative to RFLP and visible markers

We have characterized a 3547 bp DNA fragment from male-sterile (cms-T) maize mitochondria, designated TURF 2H3, selected because of its unique and abundant transcripts. Sequence analysis indicated that TURF 2H3 originated by recombinations among portions of the flanking and/or coding regions of the maize mitochondrial 26S ribosomal gene, the ATPase subunit 6 gene, and the chloroplast tRNA-Arg gene. TURF 2H3 contains two long open reading frames that could encode polypeptides of 12,961 Mr and 24,675 Mr. The larger open reading frame hybridizes to transcripts in all maize cytoplasms, the smaller to transcripts only in T cytoplasm. TURF 2H3 transcripts appear to be uniquely altered in cms-T plants restored to fertility by the nuclear restorer genes Rf1 and Rf2. A possible relationship between TURF 2H3, nuclear restorer genes, and the male sterility trait in T cytoplasm is suggested.