Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2005
Publication Date: N/A
Citation: Interpretive Summary: Major advancements in science hinge on the identification of genes controlling plant and animal traits that are critically important to agriculture. Genes are tiny packets of genetic blueprint material that are found inside the cells of all plants and animals and control all of the physical characteristics of these organisms. Our work focuses on improving major grain crops and, with gene sequences, the genetic blueprint will be visible and this information can make improving the plants more efficient. This study details the isolation of a major plant gene, named Rf1, that controls pollen viability in sorghum, and also directly compares the map location of this gene in sorghum and rice. The direct comparison of the Rf1 gene and the genes surrounding it between rice and sorghum will permit more efficient identification and understanding of the function of this gene, and will allow scientists to understand those key features of the genetic blueprint that make sorghum's physical appearance differ from that of rice. Information will be primarily used by fellow scientists but the work should ultimately result in better adapted, higher producing crop varieties available to American farmers.
Technical Abstract: With an aim to clone the sorghum pollen fertility restorer gene Rf1, a high resolution genetic and physical map of the locus was constructed. The Rf1 locus was resolved to a 32 kilobase region spanning four open reading frames; a plasma membrane ATPase, a cyclin gene, an unknown protein gene, and a pentatricopeptide repeat gene family member. A 19 kilobase sequence spanning the cyclin and unknown protein genes was completely conserved between sterile and fertile plants as was the sequence spanning the coding region of the ATPase. By contrast, 19 sequence polymorphisms were located in a seven kilobase region spanning the pentatricopeptide repeat gene, and all markers cosegregated with the fertility restoration phenotype. The pentatricopeptide repeat gene was predicted to encode a mitochondrial targeted protein containing a single exon with fourteen pentatricopeptide repeats, and the protein is classified as an E type subfamily member. To permit sequence based comparison of the sorghum and rice genomes in the Rf1 region, 530 kilobase of sorghum chromosome 08 was sequenced and compared to the collinear region of rice chromosome 12. Genome comparison revealed a mosaic pattern of colinearity with a 275 kilobase gene poor region with little gene conservation and an adjacent, 245 kilobase gene rice region that is more highly conserved between rice and sorghum. Despite being located in a region of high gene conservation, the sorghum pentatricopeptide repeat gene was not located in a colinear position on rice chromosome 12. The present results suggest that sorghum the pentatricopeptide repeat gene represents a potential candidate for the sorghum RF1 gene, and its presence in the sorghum genome indicates a single gene transposition event subsequent to the divergence of rice and sorghum ancestors.