Barros Jessica A S, Cavalcanti João Henrique F, Medeiros David B, Nunes-Nesi Adriano, Avin-Wittenberg Tamar, Fernie Alisdair R, Araújo Wagner L
Max Planck Partner Group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm, Germany.
Plant Physiol. 2017 Sep;175(1):62-76. doi: 10.1104/pp.16.01576. Epub 2017 Jul 14.
Under heterotrophic conditions, carbohydrate oxidation inside the mitochondrion is the primary energy source for cellular metabolism. However, during energy-limited conditions, alternative substrates are required to support respiration. Amino acid oxidation in plant cells plays a key role in this by generating electrons that can be transferred to the mitochondrial electron transport chain via the electron transfer flavoprotein/ubiquinone oxidoreductase system. Autophagy, a catabolic mechanism for macromolecule and protein recycling, allows the maintenance of amino acid pools and nutrient remobilization. Although the association between autophagy and alternative respiratory substrates has been suggested, the extent to which autophagy and primary metabolism interact to support plant respiration remains unclear. To investigate the metabolic importance of autophagy during development and under extended darkness, Arabidopsis () mutants with disruption of autophagy ( mutants) were used. Under normal growth conditions, mutants showed lower growth and seed production with no impact on photosynthesis. Following extended darkness, mutants were characterized by signatures of early senescence, including decreased chlorophyll content and maximum photochemical efficiency of photosystem II coupled with increases in dark respiration. Transcript levels of genes involved in alternative pathways of respiration and amino acid catabolism were up-regulated in mutants. The metabolite profiles of dark-treated leaves revealed an extensive metabolic reprogramming in which increases in amino acid levels were partially compromised in mutants. Although an enhanced respiration in mutants was observed during extended darkness, autophagy deficiency compromises protein degradation and the generation of amino acids used as alternative substrates to the respiration.
在异养条件下，线粒体内的碳水化合物氧化是细胞代谢的主要能量来源。然而，在能量受限的条件下，需要替代底物来支持呼吸作用。植物细胞中的氨基酸氧化通过产生电子发挥关键作用，这些电子可通过电子传递黄素蛋白/泛醌氧化还原酶系统转移到线粒体电子传递链。自噬是一种用于大分子和蛋白质循环利用的分解代谢机制，能够维持氨基酸库并促进养分再利用。尽管有人提出自噬与替代呼吸底物之间存在关联，但自噬与初级代谢相互作用以支持植物呼吸的程度仍不清楚。为了研究发育过程中以及长时间黑暗条件下自噬的代谢重要性，使用了自噬功能缺失的拟南芥（）突变体（突变体）。在正常生长条件下，突变体的生长和种子产量较低，而光合作用不受影响。在长时间黑暗处理后，突变体表现出早期衰老的特征，包括叶绿素含量降低、光系统II的最大光化学效率下降以及暗呼吸增加。参与呼吸替代途径和氨基酸分解代谢的基因转录水平在突变体中上调。黑暗处理叶片的代谢物谱显示出广泛的代谢重编程，其中突变体中氨基酸水平的增加部分受到影响。尽管在长时间黑暗期间观察到突变体的呼吸增强，但自噬缺陷会损害蛋白质降解以及用作呼吸替代底物的氨基酸的生成。
