Submitted to: Maize Genetics Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/18/1996
Publication Date: N/A
Technical Abstract: In T-cytoplasm male-sterile maize complementary expression of dominant nuclear alleles at rf1 and rf2 loci allows normal pollen development. Another newly described restorer, Rf8, can substitute for Rf1 to partially restore fertility to cms-T plants. Families segregating for Rf8 partial fertility restorer were used to further investigate the mechanism of this fertility restoration. Based on RFLP analyses of these families, Rf8 is unlinked to the rf1 locus. Accumulation of unique 1.6- and 0.6-kb T-urf13 mitochondrial transcripts is Rf1 dependent. To determine if Rf8 affects T-urf13 transcript accumulation in a similar manner, mitochondrial RNAs from plants segregating for the Rf8 phenotype were assayed with T-urf13 probes. Unique 1.4- and 0.4-kb T-urf13 transcripts cosegregated with partial fertility restoration in these families. Like the unique 1.6- and 0.6-kb transcripts in plants carrying Rf1, the 1.4- and 0.4-kb transcripts in plants carrying Rf8 may be RNA processing derivatives of larger T-urf13 transcripts. The 5' end of the 1.4- and 0.4-kb transcripts are approximately 110 bp 3' of the ATG initiation codon of the T-urf13 open reading frame. These putative processing sites are about 100 bp downstream of the Rf1 processing site. Accumulation of Rf1 dependent 1.6- and 0.6-kb transcripts is also associated with an 80% reduction in accumulation of URF13 protein. Plants that carry Rf8 generally do not have reduced accumulation of URF13 protein. A survey by mitochondrial RNA gel blot analyses revealed that Rf8 is rare in maize germplasm, having only been identified in 2 of 12 sources. Genetic backgrounds and environment influence penetrance and amount of fertility restored by Rf8.