Malate and citrate underpin the characteristic flexibility of central plant metabolism by linking mitochondrial respiratory metabolism with cytosolic biosynthetic pathways. However, the identity of mitochondrial carrier proteins that influence both processes has remained elusive. Here we show by a systems approach that DICARBOXYLATE CARRIER 2 (DIC2) facilitates mitochondrial malate–citrate exchange in vivo in Arabidopsis thaliana. DIC2 knockout (dic2-1) retards growth of vegetative tissues. In vitro and in organello analyses demonstrate that DIC2 preferentially imports malate against citrate export, which is consistent with altered malate and citrate utilization in response to prolonged darkness of dic2-1 plants or a sudden shift to darkness of dic2-1 leaves. Furthermore, isotopic glucose tracing reveals a reduced flux towards citrate in dic2-1, which results in a metabolic diversion towards amino acid synthesis. These observations reveal the physiological function of DIC2 in mediating the flow of malate and citrate between the mitochondrial matrix and other cell compartments.

中文翻译：

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线粒体苹果酸-柠檬酸交换支持叶片中植物有机酸代谢的多功能性

苹果酸和柠檬酸通过将线粒体呼吸代谢与细胞溶质生物合成途径联系起来，支持中央植物代谢的特征灵活性。然而，影响这两个过程的线粒体载体蛋白的身份仍然难以捉摸。在这里，我们通过系统方法显示二羧​​酸盐载体 2 (DIC2) 促进拟南芥体内线粒体苹果酸-柠檬酸交换。DIC2 敲除 (dic2-1) 会延缓营养组织的生长。体外和细胞器分析表明，DIC2 优先输入苹果酸而不是柠檬酸输出，这与响应 dic2-1 植物长时间黑暗或 dic2-1 叶子突然转变为黑暗而改变的苹果酸和柠檬酸利用一致。此外，同位素葡萄糖追踪显示 dic2-1 中柠檬酸盐的通量减少，这导致代谢转向氨基酸合成。这些观察揭示了 DIC2 在介导线粒体基质和其他细胞区室之间的苹果酸和柠檬酸流动方面的生理功能。