Abstract：
Legumes perform symbiotic nitrogen fixation through rhizobial bacteroids housed in specialised root nodules. The biochemical process is energy-intensive and consumes a huge carbon source to generate sufficient reducing power. To maintain the symbiosis, malate is supplied by legume nodules to bacteroids as their major carbon and energy source in return for ammonium ions and nitrogenous compounds. To sustain the carbon supply to bacteroids, nodule cells undergo drastic reorganisation of carbon metabolism. Here, a comprehensive quantitative comparison of the mitochondrial proteomes between root nodules and uninoculated roots was performed using data-independent acquisition proteomics, revealing the modulations in nodule mitochondrial proteins and pathways in response to carbon reallocation. Corroborated our findings with that from the literature, we believe nodules preferably allocate cytosolic phosphoenolpyruvates towards malate synthesis in lieu of pyruvate synthesis, and nodule mitochondria prefer malate over pyruvate as the primary source of NADH for ATP production. Moreover, the differential regulation of respiratory chain-associated proteins suggests that nodule mitochondria could enhance the efficiencies of complexes I and IV for ATP synthesis. This study highlighted a quantitative proteomic view of the mitochondrial adaptation in soybean nodules.
摘要：
豆科植物通过特殊根瘤中的根瘤菌进行共生固氮。生化过程是能源密集型的,并且消耗巨大的碳源以产生足够的还原力。为了保持共生，苹果酸由豆类结核提供给类细菌，作为其主要的碳和能源，以换取铵离子和含氮化合物。为了维持细菌的碳供应，结节细胞经历碳代谢的急剧重组。这里,使用独立于数据的采集蛋白质组学对根瘤和未接种根之间的线粒体蛋白质组进行了全面的定量比较，揭示了根瘤线粒体蛋白的调节和响应碳重新分配的途径。从文献中证实了我们的发现，我们认为结节优选将胞质磷酸烯醇丙酮酸分配给苹果酸合成代替丙酮酸合成，结节线粒体更喜欢苹果酸而不是丙酮酸作为产生ATP的NADH的主要来源。此外，呼吸链相关蛋白的差异调节表明结节线粒体可以增强复合物I和IV合成ATP的效率.这项研究强调了大豆结节线粒体适应的定量蛋白质组学观点。
