Stoichiometric Shifting of the Plant Mitochondrial Genome

The plant mitochondrial genome has evolved several distinguishing features that influence its structure and expression. One of these is the maintenance of subgenomic DNA molecules at markedly different copy numbers. The phenomenon of genomic shifts in copy number and the retention of substoichiometric DNA molecules within the plant mitochondrial genome will be investigated using the cytoplasmic male sterility system in common bean. This award will support two graduate students to complete their Ph.D. thesis research in two areas of this topic. The first will investigate the physiological implications of genomic shifts in the mitochondrial genome by examining the effects of shifting on cross-compatibility, the influence of temperature on the shifting process, and the plant tissues in which the mitochondrial genome is protected from shifting. The second student will investigate the expression of the mitochondrial sterility sequence, pvs-orf239, and its influence on the shifting process. This will include investigation of the export of the ORF239 product from the mitochondrion to the periphery of the cell; these particular studies will be carried out in yeast transformed with the pvs-orf239 sequence.

These investigations, through taking advantage of features special to the common bean system, address biological phenomena relevant to all higher plants, and should provide strategies for directed manipulation of the plant mitochondrial genotype.