TISSUE-SPECIFIC ACTIVITY OF 2 MANGANESE SUPEROXIDE-DISMUTASE PROMOTERS IN TRANSGENIC TOBACCO

In eukaryotes, manganese superoxide dismutase is a nuclear-encoded pro tein that scavenges superoxide radicals in the mitochondrial matrix. W e have isolated two manganese superoxide dismutase genes from Nicotian a plumbaginifolia L. and fused the 5' upstream regulatory region of th ese genes to the beta-glucuronidase reporter gene. The two gene fusion s displayed a differential tissue specificity in transgenic tobacco (N icotiana tabacum). Promoter activity of the SodA1 gene fusion was foun d in the pollen, middle layer, and stomium of anthers, but was usually undetectable in vegetative organs of mature plants. The SodA2 gene fu sion was expressed in the leaves, stems, roots, and flowers. SodA2 pro moter activity was most prominent in the vascular bundles, stomata, ax illary buds, pericycle, stomium, and pollen. Histochemical analysis of succinate dehydrogenase activity suggested that the spatial expressio n of the two gene fusions is generally correlated with mitochondrial r espiratory activity.