9729537 Mehdy Plant disease resistance mechanisms include the rapid production of active oxygen species in response to pathogen attack. Active oxygen species such as hydrogen peroxide serve as secondary messengers to mobilize changes in the expression of some defense-related genes. Dr. Mehdy and her associate's prior studies of cultured dwarf French bean cells treated with fungal elicitor provided evidence that hydrogen peroxide from the oxidative burst results in the rapid degradation of a normally stable cell wall proline-rich protein mRNA, PvPRP1. The ensuing reduced synthesis of the PvPRP1 protein is likely to contribute to remodeling of the cell wall to make it more resistant to pathogen attack. To understand the mechanism of PvPRP1 mRNA downregulation, Dr. Mehdy and her associates will focus on the biochemical characterization and cloning of a 50-kD RNA binding protein that specifically binds to the PvPRP1 MRNA. Since the purified protein requires reduced sulfhydryl group(s) for RNA binding activity, specific cellular reductants that may play a regulatory role will be investigated in in vitro assays. Thirdly, Dr. Mehdy and her associates will begin to use the genetically amenable legume species, Medicago truncatula, to screen for mutations in components that lie between pathogen-induced hydrogen peroxide and regulation of PvPRP1 mRNA expression. This study will contribute to understanding signalling pathways involving active oxygen species and suggest strategies for improving disease resistance in crops.
