Mitochondrial Factors Associated with Pollen Development

Mackenzie Abstract MCB-9316342 Recent research into the genetic interactions that occur between the nuclear and mitochondrial genomes suggests that a number of regulatory functions supplied by the nucleus are unique to higher plants. A useful class of mitochondrial mutants, giving rise to the cytoplasmic male sterility phenotype, is available for the study of these unusual nuclear-mitochondrial exchanges. We plan to take advantage of the useful features of the cytoplasmic male sterility system in common bean to investigate the role of nuclear genotype in the regulation of mitochondrial genome structure and expression, with particular emphasis on the importance of these intracellular events on the pattern of pollen development. During the course of our study, we plan to pursue two primary objectives. We intend to further characterize the expression of a mitochondrial sequence, pvs, that is associated with pollen sterility. We have developed a mitochondrial cDNA library that will allow us to determine whether the expression of pvs involves transcript splicing and to identify all encoded open reading frames transcribed from this region. We have available polyclonal antibodies against the product of a co-transcribed second open reading frame, pvs-orf98. With the transcription information and these antibodies, we will evaluate the temporal and spatial expression of the sterility-associated mitochondrial segment. This will include transcription assays as well as immunocytochemistry. Our second objective will be to evaluate the effects of two different nuclear fertility restorer genes on expression of the pvs sequence. With information gained regarding transcription of pvs, and with the use of anti-PVS antibodies, we will determine the developmental and expressional consequences of introducing the two different nuclear restorer genes. Preliminary evidence suggests that expression of pvs and its regulation are restricted to plant reproductive tissues. *** Ou r final objective will be to use the information derived from this study to identify additional nuclear genes that regulate expression of the pvs sequence. We have identified five plant lines not previously studied by our lab, each containing nuclear fertility restorer alleles. Genetic and molecular analysis using the information from this study will allow us to determine whether these nuclear genes act by mechanisms distinct from Fr and Fr2, two restorer genes already identified for CMS common bean. %%%