Molecular and Cytological Characterization of dsyCS, a Maize Mutant Defective in Homologous Chromosome Pairing During Meiosis

Indianapolis, IN

Meiotic recombination is the basis of evolutionary change over time. While recombination has been extensively studied, still little is known of the mechanisms behind this process. Many studies have suggested that recombination is in part needed for pairing of homologous chromosomes. The mutant dsyCS, which is defective in homologous chromosome pairing during meiosis, was used to further study the mechanisms of how the recombination pathway is coordinated with pairing. Previous work done in the Pawlowski lab shows that there are a substantially reduced number of RAD51 foci in the dsyCS mutant leading to a complete elimination of homologous chromosome pairing. However, it is still unknown at what stage the mutation is occurring. Immunolocalization coupled with three dimensional deconvolution microscopy was used to observe the number of foci of γ-H2AX and MLH3 proteins in wild type and mutant maize. A reduced number of γ-H2AX foci as well as a reduced number of MLH3 were detected at all the prophase stages that were observed, drawing the conclusion that in dsyCS mutants the formation of double strand breaks were impaired. The more knowledge about the mechanisms behind meiosis can have many applications, including plant breeding, cancer genetics, and birth defects.