Molecular Analysis of Meiotic Recombination and Genomic Organization in the Bronze Region of Maize

Rutgers University New Brunswick, New Brunswick NJ

Investigators

Abstract

Homologous meiotic recombination is an important process for sexually reproducing organisms: it creates new genotypes by shuffling chromosomal segments that otherwise would be inherited as a unit and promotes fertility by ensuring that chromosomes segregate properly at meiosis. For close to a century, geneticists have been using recombination as a tool to construct genetic maps, which now find practical applications ranging from risk prediction for inherited deleterious alleles to marker-assisted selection of desirable genotypes in agriculture and map-based cloning of valuable genes in plants and animals. Yet, in spite of its importance, our knowledge of the process of homologous meiotic recombination in higher plants is rudimentary compared to other organisms, like yeast. This project will increase our understanding of this basic biological process in maize, a plant that is both an excellent model organism for studies of recombination, and an economically important crop in American agriculture and industry. The genetic system being used in the project is the bz locus, which affects seed pigmentation and is uniquely advantageous for studies of recombination. This project will continue the analysis of meiotic recombination in maize by combining the power of the genetics of the bz region with that of modern molecular tools. It is greatly influenced by the recent finding that the organization of genes and retrotransposons in the bz genomic region is polymorphic in different maize lines. There are five specific objectives of the project: 1. To analyze conversion tract lengths within the bz gene island in heterozygotes lacking heterologies and extend the analysis to adjacent retrotransposon blocks. 2. To determine if the apparent conversion polarity at bz, detected with small insertion mutations at the 5' and 3' ends of the gene, but not with more centrally located point mutations, is due to the nature or the position of the mutations. 3. To test whether the presence of a highly methylated retrotransposon block affects recombination in adjacent genes. 4. To determine if all recombination junctions in an interval made up of genes and retrotransposons fall in genes. 5. To test if recombination between two sites in the genome separated by a different number of genes in different lines is a function of the number of common genes in the intervening segment.