Mackenzie 9630252 A mutation in the mitochondra of the common bean, Phaseolus vulgaris, results in male sterility. The mutation is dominant, non-lethal and can be suppressed by nuclear genome suppressors. A mitochondrial sterility-associated protein, designated pvsORF239, is found only in reproductive tissues of the male-sterile plant localized to the pollen wall. It appears to be posttranslationally regulated. The possibility that, by virtue of specific characteristics found in this protein, it is actively transported from the mitochondrion to the callose layer of the developing pollen will be investigated by genetic methodology. Other aspects to be investigated are the possible involvement of a mitochondrial protease in the rapid turnover of the protein in the mitochondria of vegetative tissues and the function of nuclear suppressors, if any, in either the transport or turnover of the protein. In order to pursue these questions in a more tractable organism, the system will be introduced into yeast for further study. %%% This investigation of the cytoplasmic male sterility system in common bean will give added insight into our limited understanding of mitochondrial export mechanisms, the tissue-specific regulation of plant mitochondrial gene expression and the molecular basis of nuclear suppression of a mitochondrially-induced phenotype.
