HOW DO ALTERATIONS IN PLANT MITOCHONDRIAL GENOMES DISRUPT POLLEN DEVELOPMENT

Cytoplasmic male sterility arises when mitochondrial activities are di srupted that are essential for pollen development. Rearrangements in t he mitochondrial genome that create novel open reading frames are stro ngly correlated with CMS phenotypes in a number of systems. The morpho logical aberrations which indicate CMS-associated degeneration are fre quently restricted to the male sporogenous tissue and a limited number of vegetative tissues. In several cases, this tissue specificity may result from interactions between the mitochondrial genome and nuclear genes that regulate mitochondrial gene expression. A molecular mechani sm by which CMS might be caused has not been conclusively demonstrated for any system. Several hypotheses for general mechanisms by which mi tochondrial dysfunction might disrupt pollen development are discussed , based on similarities between the novel CMS-associated genes from a number of systems.