Flores-Tornero María, Anoman Armand D, Rosa-Téllez Sara, Toujani Walid, Weber Andreas P M, Eisenhut Marion, Kurz Samantha, Alseekh Saleh, Fernie Alisdair R, Muñoz-Bertomeu Jesús, Ros Roc
Departament de Biologia Vegetal, Facultat de Farmácia, Universitat de València, Burjassot, Spain.
Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València, Dr Moliner 50, 46100 Burjassot, Spain.
Plant J. 2017 Mar;89(6):1146-1158. doi: 10.1111/tpj.13452. Epub 2017 Feb 11.
The presence of two glycolytic pathways working in parallel in plastids and cytosol has complicated the understanding of this essential process in plant cells, especially the integration of the plastidial pathway into the metabolism of heterotrophic and autotrophic organs. It is assumed that this integration is achieved by transport systems, which exchange glycolytic intermediates across plastidial membranes. However, it is unknown whether plastidial and cytosolic pools of 3-phosphoglycerate (3-PGA) can equilibrate in non-photosynthetic tissues. To resolve this question, we employed Arabidopsis mutants of the plastidial glycolytic isoforms of glyceraldehyde-3-phosphate dehydrogenase (GAPCp) that express the triose phosphate translocator (TPT) under the control of the 35S (35S:TPT) or the native GAPCp1 (GAPCp1:TPT) promoters. TPT expression under the control of both promoters complemented the vegetative developmental defects and metabolic disorders of the GAPCp double mutants (gapcp1gapcp2). However, as the 35S is poorly expressed in the tapetum, full vegetative and reproductive complementation of gapcp1gapcp2 was achieved only by transforming this mutant with the GAPCp1:TPT construct. Our results indicate that the main function of GAPCp is to supply 3-PGA for anabolic pathways in plastids of heterotrophic cells and suggest that the plastidial glycolysis may contribute to fatty acid biosynthesis in seeds. They also suggest a 3-PGA deficiency in the plastids of gapcp1gapcp2, and that 3-PGA pools between cytosol and plastid do not equilibrate in heterotrophic cells.
在质体和细胞质中并行运作的两条糖酵解途径的存在，使得对植物细胞这一基本过程的理解变得复杂，尤其是质体途径与异养和自养器官代谢的整合。据推测，这种整合是通过转运系统实现的，该系统可跨质体膜交换糖酵解中间产物。然而，尚不清楚在非光合组织中，3-磷酸甘油酸（3-PGA）的质体库和细胞质库是否能够达到平衡。为了解决这个问题，我们使用了拟南芥中甘油醛-3-磷酸脱氢酶（GAPCp）质体糖酵解同工型的突变体，这些突变体在35S（35S:TPT）或天然GAPCp1（GAPCp1:TPT）启动子的控制下表达磷酸丙糖转运体（TPT）。在这两个启动子控制下的TPT表达弥补了GAPCp双突变体（gapcp1gapcp2）的营养发育缺陷和代谢紊乱。然而，由于35S在绒毡层中表达水平较低，只有用GAPCp1:TPT构建体转化该突变体才能实现gapcp1gapcp2的完全营养和生殖互补。我们的结果表明，GAPCp的主要功能是为异养细胞质体中的合成代谢途径提供3-PGA，并表明质体糖酵解可能有助于种子中的脂肪酸生物合成。它们还表明gapcp1gapcp2质体中存在3-PGA缺乏，并且在异养细胞中，细胞质和质体之间的3-PGA库不会达到平衡。
