H+-PPase acidifies the endo-membrane compartments utilizing the energy of PPi hydrolysis. This acidification creates an electrochemical proton gradient that powers the secondary active transport and allows for vacuolar accumulation of several materials against their concentration gradients. The hydrolysis of the cytosolic PPi is necessary for the forwardness of the PPi-generating reactions. However, information is lacking on the role of PPi in adaptation to sugar starvation and low energy status in plants. Here, several mutants lacking the functional H+-PPases were used to illuminate this role. Three alleles of fugu5 mutants defective in type I H+-PPase exhibited better tolerance to sugar starvation than wild-type plants, when grown on half and full-strength MS media under photosynthesis-constraining low light intensity. The PPi level in fugu5 mutants was significantly higher than its level in wild type and type II H+-PPase-defective mutants. SnRK1 (Sucrose-non-fermenting1-Related kinase-1) plays a central role in the coordination of the plant transcriptome to the energy signals. SnRK1 senses the energy depletion in plant cells, and controls the expression of genes and phosphorylation of proteins in a way that promotes catabolism, and inhibits anabolism. Sugar starvation significantly induced the SnRK1 phosphorylation activity in wild type and type II H+-PPase lacking mutants. Whereas the activity remained unchanged in sugar-starved fugu5 mutants. This is possibly achieved through activation of PPi-dependent enzymes. Results suggest that the high PPi level in fugu5 mutants might contribute to more efficiently use of low level of ATP under sugar starvation and low light conditions.

中文翻译：

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PPi在糖饥饿耐受性中发挥作用

H + -PPase利用PPi水解的能量来酸化内膜隔室。这种酸化作用产生了一个电化学的质子梯度，该梯度为二次活性传输提供了动力，并允许数种物质相对于其浓度梯度进行液泡积累。胞质PPi的水解对于PPi生成反应的进行是必要的。但是，缺乏有关PPi在适应植物糖饥饿和低能量状态中的作用的信息。在这里，几个缺乏功能性H + PPases的突变体被用来阐明这一作用。当在光合作用限制的低光强度下在半强度和全强度MS培养基上生长时，I H + -PPase缺陷型的fugu5突变体的三个等位基因显示出比野生型植物更好的耐糖饥饿性。fugu5突变体中的PPi水平显着高于野生型和II型H + -PPase缺陷型突变体中的PPi水平。SnRK1（蔗糖非发酵1-相关激酶-1）在植物转录组与能量信号的协调中起着核心作用。SnRK1感应植物细胞中的能量消耗，并以促进分解代谢和抑制合成代谢的方式控制基因的表达和蛋白质的磷酸化。在缺乏突变体的野生型和II型H + -PPase中，糖饥饿显着诱导了SnRK1磷酸化活性。而在糖饥饿的fugu5突变体中，活性保持不变。这可能是通过激活PPi依赖性酶来实现的。