Elucidation of the role of the vacuolar type proton pyrophosphatase in early stages of plant development

发芽后，油籽植物依靠三酰甘油（TAG）储备在异养期生长，TAG在此期间转化为蔗糖（Suc）。此外，大分子合成需要消耗大量的ATP，这些ATP通常被水解成AMP和PPi。在拟南芥中，液泡H+-PPase利用PPi水解产生的能量使液泡酸化。fugu5突变体缺乏AVP1 H+-PPase，不能维持萌发后的异养生长；或通过胞质PPase IPP1特异性去除PPi。因此，H+-PPase在幼苗发育中的主要作用是去除抑制PPi，而不是泵送H+。WT与fugu5的结果表明，PPi水平升高可抑制糖异生，但抑制的靶点尚不清楚。在这里，TAG动员过程中发生的主要代谢物分析显示，fugu5中过量的胞质PPi特异性抑制了udp -葡萄糖焦磷酸化酶（UGPase）。

Following germination, oil-seed plants rely on triacylglycerol (TAG) reserves for growth during a heterotrophic period, where TAG is converted to sucrose (Suc). Also, macromolecular syntheses consume huge amounts of ATP, often hydrolyzed to AMP plus PPi. In Arabidopsis, the vacuolar H+-PPase uses energy from PPi hydrolysis to acidify the vacuole. The fugu5 mutants, lacking the AVP1 H+-PPase, failed to sustain postgerminative heterotrophic growth; recovered upon Suc supply, or specific PPi removal by the cytosolic PPase IPP1. Thus the major function of H+-PPase in seedling development is the removal of inhibitory PPi, rather than H+ pumping. Suc and PPi quantification in WT versus fugu5 indicated that gluconeogenesis is inhibited by elevated level of PPi, but the targets of PPi inhibition remained unclear. Here, profiling of major metabolites that occur during TAG mobilization showed that UDP-Glucose Pyrophosphorylase (UGPase) is specifically inhibited by excess cytosolic PPi in fugu5.