Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/1996
Publication Date: N/A
Interpretive Summary: Cytoplasmic male sterility (cms) is of significant value in the production of maize hybrids. A line carrying the cms trait does not produce pollen, thus eliminating the time consuming, and labor-intensive need for manual detasseling. Cms in T or "Texas" male-sterile cytoplasm has been attributed to the presence of the unique mitochondrial gene, T-urf13. However, T-urf13 function can be suppressed, "restoring" T-cytoplasm plants to fertility, thereby allowing hybrids to be made. Restoration of pollen fertility in T-cytoplasm maize is mediated by two nuclear genes; Rf1 and Rf2. To investigate the role of Rf1 in pollen development, maize lines were identified that were defective for this gene. These lines also affected the molecular functions of the T-urf13 gene, demonstrating that T-urf13 function is dependent on Rf1. Genetic stocks produced by this study will be a valuable resource for the molecular isolation and characterization of the Rf1 gene, furthering our understanding of normal pollen and flower development. Since cytoplasmic male sterility plays an important role in breeding programs, a basic understanding of the the role of this restorer gene on pollen fertility will impact U. S. Agriculture by improving the science of crop production.
Technical Abstract: Dominant alleles at the rf1 and rf2 nuclear-encoded fertile restorer genes are necessary for restoration of pollen fertility in T-cytoplasm maize. To further characterize fertility restoration mediated by the Rf1 allele, 123,500 gametes derived from plants carrying the Mutator transposable element family were screened for rf1-mutant alleles (rf1-m). Four heritable rf1-m alleles were recovered from these populations. Three rf1-m alleles were derived from the progenitor allele Rf1-IA153 and one was derived from Rf1-Ky21. Mitochondrial RNA gel blot analyses indicated that male-sterile plants carrying the four rf1-m alleles cosegregated with the altered steady-state accumulation of 1.6- and 0.6-kb T-urf13 transcripts, demonstrating that these transcripts are Rf1 dependent. Plants carrying a leaky mutant, rf1-m7323, revealed variable levels of Rf1-associated, T-urf13 transcripts and the degree of pollen fertility. The ability to obtain rf1-m derivatives from Rf1 indicates that Rf1 alleles produce a functional gene product necessary for the accumulation of specific T-urf13 transcripts in T-cytoplasm maize.