College of Horticulture, Gansu Agricultural University, Lanzhou, Gansu, China.
PeerJ. 2022 Aug 24;10:e13691. doi: 10.7717/peerj.13691. eCollection 2022.
The content and the ratio of soluble sugars and organic acids in fruits are significant indicators for fruit quality. They are affected by multiple environmental factors, in which water-deficient is the most concern. Previous studies found that the content of soluble sugars and organic acids in fruit displayed great differences under varied water stress. It is important to clarify the mechanism of such difference and to provide researchers with systematic knowledge about the response to drought stress and the mechanism of sugar and acid changes in fruits, so that they can better carry out the study of fruit quality under drought stress. Therefore, the researchers studied dozens of research articles about the content of soluble sugar and organic acid, the activity of related metabolic enzymes, and the expression of related metabolic genes in fruits under water stress, and the stress response of plants to water stress. We found that after plants perceived and transmitted the signal of water deficit, the expression of genes related to the metabolism of soluble sugars and organic acids changed. It was then affected the synthesis of metabolic enzymes and changed their metabolic rate, ultimately leading to changes in soluble sugar and organic acid content. Based on the literature review, we described the pathway diagrams of sugar metabolism, organic acid metabolism, mainly malic acid, tartaric acid, and citric acid metabolism, and of the response to drought stress. From many aspects including plants' perception of water stress signal, signal conversion and transmission, induced gene expression, the changes in soluble sugar and the enzyme activities of organic acids, as well as the final sugar and acid content in fruits, this thesis summarized previous studies on the influence of water stress on soluble sugars and the metabolism of organic acids in fruits.
果实中可溶性糖和有机酸的含量和比例是果实品质的重要指标。它们受到多种环境因素的影响，其中水分亏缺最为关注。先前的研究发现，在不同的水分胁迫下，果实中可溶性糖和有机酸的含量存在很大差异。阐明这种差异的机制，为研究人员提供关于植物对干旱胁迫的响应以及果实中糖和酸变化的机制的系统知识，使他们能够更好地在干旱胁迫下进行果实品质研究，这一点非常重要。因此，研究人员研究了几十篇关于水分胁迫下果实中可溶性糖和有机酸含量、相关代谢酶活性以及相关代谢基因表达以及植物对水分胁迫的应激反应的研究文章。我们发现，植物感知和传递水分亏缺信号后，与可溶性糖和有机酸代谢相关的基因表达发生变化。这继而影响代谢酶的合成并改变其代谢速率，最终导致可溶性糖和有机酸含量的变化。基于文献综述，我们描述了糖代谢、有机酸代谢（主要是苹果酸、酒石酸和柠檬酸代谢）以及对干旱胁迫响应的途径图。从植物对水分胁迫信号的感知、信号转换和传递、诱导基因表达、可溶性糖的变化以及有机酸的酶活性，以及最终果实中的糖和酸含量等多个方面，本文总结了先前关于水分胁迫对果实中可溶性糖和有机酸代谢的影响的研究。
