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

苹果酸是C3代谢的重要中间体，作为三羧酸和乙醛循环的组成部分，参与气孔运动，控制细胞液pH，维持细胞电平衡，是固定碳的重要形式。由于苹果酸的合成或去除所涉及的酶的普遍存在，以及特定的膜载体的存在，苹果酸在所有的细胞室中都存在并经历着转化。这项建议是基于我们最近发表的工作，旨在澄清拟南芥苹果酸稳态的几个方面，特别是对苹果酸脱羧酶(NAD-和NADP-ME)的生物学功能的阐明。计划中的工作包括产生和鉴定由于特定细胞类型或亚细胞隔间缺乏或过度表达NAD-和NADP-ME活性而导致苹果酸和富马酸含量改变的转基因植物。通过将代谢通量的测量与代谢图谱、蛋白质组分析和转录组分析相结合来评估对C-和N-代谢的影响，将研究确定的活性的过度表达或缺乏表达对代谢通量重定向的影响。不同方法的综合结果有望为植物二元酸代谢提供新的线索。

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.