|Samac, Deborah - Debby|
Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 8/2/1997
Publication Date: N/A
Technical Abstract: The primary assimilation of ammonia into amino acids in higher plants whether the nitrogen is derived from symbiotic nitrogen fixation or the reduction of soil derived nitrate occurs via the concerted action of four enzymes. The first two, referred to as the glutamate cycle, are catalyzed by glutamine synthetase and glutamate synthase; they are responsible for the synthesis of glutamine and glutamate. Subsequent incorporation of nitrogen into aspartate and asparagine occurs through aspartate aminotransferase and asparagine synthase. The carbon skeletons required for the initial assimilation of nitrogen into amino acids are derived from the organic acids oxaloacetate and alpha-ketoglutarate. The production of oxaloacetate occurs primarily through phosphoenolpyruvate carboxylase and malate dehydrogenase. The long term goal of our research is to determine the biochemical and molecular processes that regulate root nodule development and function. An increased understanding of these processes should enable us to enhance the efficiency of symbiotic nitrogen fixation and nitrogen assimilation in alfalfa. To achieve this goal we have utilized both overexpression and antisense technology to modulate the expression of these key nitrogen assimilatory enzymes in alfalfa using both constitutive (CaMV 35S) and nodule specific promoters. Results from the biochemical and molecular analysis of transgenic alfalfa containing these constructs will be presented. Funds for this research were provided in part by NSF grant IBN-9206890.