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United States Department of Agriculture

Agricultural Research Service

Title: Modulation of Nitrogen Assimilation in Transgenic Alfalfa

Authors
item Temple, Stephen - UNIVERSITY OF MINNESOTA
item Schoenbeck, Mark - UNIVERSITY OF MINNESOTA
item Shi, Lifang - UNIVERSITY OF MINNESOTA
item Samac, Deborah
item Gantt, J - UNIVERSITY OF MINNESOTA
item Vance, Carroll

Submitted to: Keystone Symposia on Molecular and Cellular Biology
Publication Type: Abstract Only
Publication Acceptance Date: April 7, 1997
Publication Date: N/A

Technical Abstract: The primary assimilation of ammonia into amino acids in higher plants whether derived from nitrogen fixation or 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 and 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 skeleton required for the initial assimilation of nitrogen into amino acids is 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 and enhance the efficiency of symbiotic nitrogen fixation and assimilation in alfalfa. To achieve this goal we have utilized overexpression and antisense technology to modulate the expression on these key nitrogen assimilatory enzymes in alfalfa using both constitutive (CaMV 35S) and nodule specific (Leghemoglobin) promoters. Results from biochemical and molecular analysis of transgenic alfalfa will be presented. Funds for this research were provided in part by NSF grant IBN-9206890.

Last Modified: 4/19/2014
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