Impairment of tapetum and mitochondria in engineered male-sterile tobacco plants.

Flowers of tobacco transformed with an unedited copy of the mitochondrial atp9 gene sequence fused to the yeast coxIV mitochondrial targeting presequence, showed several anther abnormalities leading to pollen abortion. The gene was expressed in vegetative and reproductive tissues of the plant. Cytological analysis revealed that tapetum development was impaired. Mitochondria of the tapetum cells were severely affected showing characteristic signs of degeneration: loss of cristae and swelling. These mitochondrial modifications were correlated with the presence of the transcript and translated product of the 'unedited' atp9 and a significant decrease in oxygen consumption in non-photosynthetic tissues. The main effect of the unedited atp9 expression in transgenic plants was male sterility.