The goal of this project is to understand the fundamental role of malate metabolism in plant cells. 13C NMR spectroscopy is being used to determine the compartmentation of malate between cytoplasm and vacuole in maize root tips. These determinations are coupled with in vivo and in vitro measurements of malate synthesis, decarboxylation, vacuolar transport and the conversion of malate to other metabolites to obtain a comprehensive picture of the behavior of malate within the cell. The results of these analyses will help establish 1) the extent to which malate (versus pyruvate) is the major metabolite utilized to drive the operation of the TCA cycle in plant mitochondria, 2) the role of malate in the regulation of PEP carboxylase activity in the cytoplasm and 3) the interplay between cytosolic bicarbonate levels and malate metabolism in response to salt stress.%%% Malic acid (malate) has long been recognized for its potential as a major intermediate compound associated with respiratory and related metabolisms in higher plant cells. However, the exact importance of malate has eluded precise clarification due to a lack of ability to measure malate and its rates of synthesis/breakdown within the intact cell. This project uses NMR spectroscopy, coupled with a series of more classical biochemical assays, to look at the levels. rates and directions of movement of malate within corn root tip cells to develop a precise picture of the role of malate in plant respiratory metabolism. A better understanding of the function of malate in plant respiration should lead to a clearer picture of what factors act to regulate plant respiration and, ultimately, plant productivity.***
