ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009, Western Australia, Australia.
Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 8, D-48143 Münster, Germany.
Plant Cell. 2021 Dec 3;33(12):3700-3720. doi: 10.1093/plcell/koab223.
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.
苹果酸和柠檬酸通过将线粒体呼吸代谢与胞质生物合成途径联系起来，为中心植物代谢的特征灵活性提供支持。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，我们通过系统方法表明，二羧酸载体 2（DIC2）在拟南芥体内促进线粒体苹果酸-柠檬酸交换。DIC2 敲除（dic2-1）会减缓营养组织的生长。体外和细胞器分析表明，DIC2 优先导入苹果酸而不是柠檬酸输出，这与 dic2-1 植物长时间黑暗或 dic2-1 叶片突然转入黑暗时对苹果酸和柠檬酸的利用改变一致。此外，同位素葡萄糖示踪表明 dic2-1 中的柠檬酸通量减少，导致代谢向氨基酸合成转移。这些观察结果揭示了 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中的生理功能。
