IMPAIRMENT OF TAPETUM AND MITOCHONDRIA IN ENGINEERED MALE-STERILE TOBACCO PLANTS

Flowers of tobacco transformed with an unedited copy of the mitochondr ial atp9 gene sequence fused to the yeast coxIV mitochondrial targetin g presequence, showed several anther abnormalities leading to pollen a bortion. 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 swe lling. These mitochondrial modifications were correlated with the pres ence of the transcript and translated product of the 'unedited' atp9 a nd a significant decrease in oxygen consumption in non-photosynthetic tissues. The main effect of the unedited atp9 expression in transgenic plants was male sterility.