TRANSFER OF METHOMYL AND HMT-TOXIN SENSITIVITY FROM T-CYTOPLASM MAIZE TO TOBACCO

The mitochondrial gene, T-urf13, which is unique to the T-cytoplasm of maize, has been expressed in tobacco plants using the Cauliflower Mosaic Virus 35S promoter. Tobacco plants expressing T-urf13 exhibit a variety of responses to methomyl. Leaf discs and petiole sections bleach when exposed to methomyl or HmT-toxin; this effect increases with the age of the tissue. The bleaching effect is not however observed when light is excluded. Plants homozygous for T-urf13 exhibit extreme sensitivity when sprayed with methomyl. The growth of seedling which are either homozygous or heterozygous for T-urf13 is inhibited by methomyl and by kanamycin, whereas seedlings from untransformed tobacco or tobacco which has lost the T-urf13 gene through segregation are sensitive to kanamycin but develop normally when exposed to methomyl. The results demonstrate that T-URF13 need not be specifically targeted to the mitochondrion for it to induce methomyl or HmT-toxin sensitivity in tobacco.