Department of Plant Breeding, Swedish University of Agricultural Sciences, Alnarp, Sweden.
Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg, Potsdam-Golm, Germany.
J Exp Bot. 2018 Apr 9;69(8):1913-1924. doi: 10.1093/jxb/ery051.
The importance of a plastidial soluble inorganic pyrophosphatase (psPPase) and an ATP/ADP translocator (NTT) for starch composition and tuber formation in potato (Solanum tuberosum) was evaluated by individual and simultaneous down-regulation of the corresponding endogenous genes. Starch and amylose content of the transgenic lines were considerably lower, and granule size substantially smaller, with down-regulation of StpsPPase generating the most pronounced effects. Single-gene down-regulation of either StpsPPase or StNTT resulted in increased tuber numbers per plant and higher fresh weight yield. In contrast, when both genes were inhibited simultaneously, some lines developed only a few, small and distorted tubers. Analysis of metabolites revealed altered amounts of sugar intermediates, and a substantial increase in ADP-glucose content of the StpsPPase lines. Increased amounts of intermediates of vitamin C biosynthesis were also observed. This study suggests that hydrolysis of pyrophosphate (PPi) by action of a psPPase is vital for functional starch accumulation in potato tubers and that no additional mechanism for consuming, hydrolysing, or exporting PPi exists in the studied tissue. Additionally, it demonstrates that functional PPi hydrolysis in combination with efficient ATP import is essential for tuber formation and development.
通过分别和同时下调相应的内源性基因，评估了质体可溶性无机焦磷酸酶（psPPase）和 ATP/ADP 转运蛋白（NTT）对马铃薯（Solanum tuberosum）淀粉组成和块茎形成的重要性。转基因品系的淀粉和直链淀粉含量明显降低，颗粒尺寸显著减小，StpsPPase 的下调产生的影响最为显著。StpsPPase 或 StNTT 的单基因下调导致每株植物的块茎数量增加和鲜重产量增加。相比之下，当同时抑制这两个基因时，一些品系只形成少量、小而畸形的块茎。代谢物分析显示糖中间产物的含量发生了变化，StpsPPase 品系的 ADP-葡萄糖含量也显著增加。还观察到维生素 C 生物合成中间产物的增加。本研究表明，psPPase 作用下水解焦磷酸（PPi）对于马铃薯块茎中功能性淀粉的积累至关重要，而且在所研究的组织中不存在消耗、水解或输出 PPi 的其他机制。此外，它表明功能性 PPi 水解与有效的 ATP 导入相结合对于块茎形成和发育是必不可少的。
