|Samac, Deborah - Debby|
Submitted to: Nitrogen Fixation International Congress
Publication Type: Abstract Only
Publication Acceptance Date: 7/3/2001
Publication Date: N/A
Technical Abstract: Malate plays a key role in symbiotic nitrogen fixation by providing the substrate for bacteroid respiration, thus fueling nitrogenase, and by providing the carbon skeletons for assimilation of fixed nitrogen. Malate may also play a role in regulating the nodule variable oxygen diffusion barrier. To define genetic and biochemical regulation of root nodule malate eformation, we isolated the alfalfa genes encoding cytosolic and nodule enhanced malate dehydrogenase (MDH: EC 22.214.171.124). Protein and mRNA localization showed that nodule enhanced MDH was localized predominantly in plastids of infected and uninfected cells while cytosolic MDH occurred primarily in uninfected cells. Localization of these enzymes in distinct cell types of root nodules may differentiate function for symbiotic nitrogen fixation. Initial studies suggest over-expression of nodule enhanced MDH in alfalfa may enhance nitrogen fixation and improve aluminum tolerance.