Submitted to: Maize Genetics Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/1997
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: A 13-kD mitochondrial inner-membrane protein, URF13, is associated with male sterility in T-cytoplasm maize (cmsT). cmsT maize is restored to fertility by the combined action of dominant alleles of two nuclear genes, rf1 and rf2. In restored cms-T plants, Rf1 mediates a 70-80% reduction in the accumulation of URF13; the function of Rf2 in fertility restoration is unknown. The rf2 gene was recently cloned (Cui et al., 1996 Science 272:134) and shown to exhibit 75% similarity and 60% identity at the amino acid level with mammalian mitochondrial aldehyde dehydrogenases (ALDH). A full-length rf2 cDNA has been expressed in E. coli. Immunoblot analyses with polyclonal antibodies raised against this expressed protein detected the maize RF2 protein in extracts from all organs and developmental stages examined, including seedlings, tassels, stems, roots and mature leaves. These analyses also revealed that the RF2 protein forms a multimeric complex in maize cells. The deduced amino acid sequence of RF2 contains a mitochondrial targetting sequence. Subcellular fractionation experiments have confirmed that the RF2 protein accumulates in the mitochondria. Efforts are underway, using extracts from Rf2-expressing E. coli and maize, to identify the substrate specificity of this predicted aldehyde dehydrogenase. URF13 that is targeted to yeast mitochondria is known to confer sensitivity to HmT toxin and methomyl. The effect of Rf2-expression in such yeast strains is being determined. The positions of Mu transposon insertions associated with five of the seven rf2-m alleles have been determined within the >19 kb rf2 gene. These insertion sites are being correlated with allelic differences in Mu-suppression.