Aix-Marseille University, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Commissariat à l'Energie Atomique Cadarache, Saint-Paul-lez Durance F-13108, France.
Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany.
Plant Physiol. 2019 Apr;179(4):1502-1514. doi: 10.1104/pp.18.01584. Epub 2019 Feb 6.
Nitrogen (N) starvation-induced triacylglycerol (TAG) synthesis, and its complex relationship with starch metabolism in algal cells, has been intensively studied; however, few studies have examined the interaction between amino acid metabolism and TAG biosynthesis. Here, via a forward genetic screen for TAG homeostasis, we isolated a () mutant () that is deficient in the E1α subunit of the branched-chain ketoacid dehydrogenase (BCKDH) complex. Metabolomics analysis revealed a defect in the catabolism of branched-chain amino acids in Furthermore, this mutant accumulated 30% less TAG than the parental strain during N starvation and was compromised in TAG remobilization upon N resupply. Intriguingly, the rate of mitochondrial respiration was 20% to 35% lower in compared with the parental strains. Three additional knockout mutants of the other components of the BCKDH complex exhibited phenotypes similar to that of Transcriptional responses of to different N status were consistent with its role in TAG homeostasis. Collectively, these results indicate that branched-chain amino acid catabolism contributes to TAG metabolism by providing carbon precursors and ATP, thus highlighting the complex interplay between distinct subcellular metabolisms for oil storage in green microalgae.
氮饥饿诱导的三酰基甘油(TAG)合成及其与藻类细胞中淀粉代谢的复杂关系已得到深入研究；然而，很少有研究探讨氨基酸代谢与 TAG 生物合成之间的相互作用。在这里，我们通过正向遗传筛选 TAG 稳态，分离出一个 ()突变体 ()，该突变体缺乏支链酮酸脱氢酶 (BCKDH) 复合物的 E1α 亚基。代谢组学分析显示，在 中支链氨基酸的分解代谢存在缺陷。此外，与亲本菌株相比，该突变体在氮饥饿期间积累的 TAG 减少了 30%，在氮供应恢复时 TAG 的再动员受到损害。有趣的是，与亲本菌株相比， 中的线粒体呼吸率降低了 20%至 35%。另外三个 BCKDH 复合物其他成分的敲除突变体表现出与 相似的表型。对不同氮状态下 的转录反应与其在 TAG 稳态中的作用一致。总之，这些结果表明，支链氨基酸的分解代谢通过提供碳前体和 ATP 来促进 TAG 代谢，从而突出了不同亚细胞代谢之间在绿色微藻中储存油脂的复杂相互作用。
