|Samac, Deborah - Debby|
Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/1996
Publication Date: N/A
Technical Abstract: NADH-dependent glutamate synthase (GOGAT) catalyzes the transamination of the amide nitrogen of glutamate to alpha-ketoglutarate to produce two molecules of glutamate. In root nodules of Medicago sativa, a nodule enhanced form of NADH-GOGAT is responsible for the second step in the assimilation of symbiotically produced ammonia. To determine whether this represents a limited step in symbiotic nitrogen fixation, we have transformed alfalfa with an antisense NADH-GOGAT cDNA fragment driven by the nodule-enhanced aspartate aminotransferase-2 promoter. Among the transformed regenerated plants, most have nodule NADH-GOGAT activity comparable to transformed control plants. One genotype, however, has nodule NADH-GOGAT activity reduced to approximately 50 percent of the control activity. This reduced activity corresponds to a reduction in the amount of NADH-GOGAT protein, as determined by Western blots, and a significant reduction in shoot dry matter. We report also the effect of this reduced activity on plant total N and nodule free amino acid metabolite pools.