Some of the most interesting questions being addressed in higher eukaryotic organisms concern the regulation of gene expression at particular stages of development that involve communication between subcellular organelles. The model system that has been developed in cytoplasmic male sterile common bean provides ideal genetic materials to address these questions. The system has a number of unique features. Two distinct nuclear-mito- chondrial genetic interactions have been identified that result in an altered pollen phenotype. Evidence suggests that at least some aspects of this interorganellar interaction are developmentally regulated. The focus of this study is a mitochondrial sequence, designated pvs, associated with abnormal pollen development. The project includes development of antibodies against the putative products of two open reading frames within pvs. These antibodies will characterize the expression of the two predicted mitochondrial products in response to the presence of nuclear gene Fr. Fr results in the elimination of the pvs sequence together with the surrounding mitochondrial region. A second nuclear gene, Fr2, is predicted to alter expression of pvs. Both Fr and Fr2 restore normal pollen development. The experiments will include Western blot analysis, immunoprecipitations, and in situ backcross and F2 populations, the cytoplasmic male sterile line, a number of spontaneous cytoplasmic fertile revertants, and a normal control line. The proposed research will also include characterization of transcription of the mitochondrial pvs region. The experiments will characterize the developmental expression of a mitochondrial sequence in response to two distinct nuclear genes that alter pollen development. The experiments will also identify potential regulatory sites within this mitochondrial sequence.
