Plant dicarboxylic acid homeostasis: on the specific physiological role of enzymes involved in malate decarboxylation

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Malate is an important intermediate in C3 metabolism as a component of the tricarboxylic acid and the glyoxylate cycles, it participates in stomatal movements, in the control of cytosolic pH, the maintenance of the cell electrical balance and is an important form of fixed carbon. Malate is present and undergoes transformations in all cell compartments due to the ubiquitous presence of enzymes involved in its synthesis or removal and of specific membrane carriers. This proposal, which is based on our recently published work, was designed to clarify several aspects of malate homeostasis in Arabidopsis thaliana with special focus on the elucidation of the biological function of malate decarboxylating enzymes (NAD-and NADP-ME). The planned work involves the generation and characterization of transgenic plants with altered malate and fumarate contents due to the lack or overexpression of NAD- and NADP-ME activities in specific cellular types or subcellular compartments. The effects of the overexpression or the lack of expression of a determined activity on the redirection of metabolic fluxes will be investigated by combining the measurement of metabolic fluxes with metabolic profiling, proteomic analysis and transcriptome analysis to assess the impact on C- and N-metabolism. The combined results of the different approaches are expected to shed new light on plant dicarboxylic acid metabolism.