Zhang Lihua, Wang Changzhi, Jia Runpu, Yang Nanxiang, Jin Ling, Zhu Lingcheng, Ma Baiquan, Yao Yu-Xin, Ma Fengwang, Li Mingjun
State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China.
The Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Northeast Region), Ministry of Agriculture and Rural Affairs, College of Horticulture & Landscape Architecture, Northeast Agricultural University, Harbin 150030, China.
Hortic Res. 2022 Nov 1;9:uhac194. doi: 10.1093/hr/uhac194. eCollection 2022.
The types and proportions of soluble sugar and organic acid in fruit significantly affect flavor quality. However, there are few reports on the crosstalk regulation between metabolism of organic acid and sugar in fruit. Here, we found that the overexpression of cytoplasmic malate dehydrogenase genes () not only increased the malate content but also increased the sucrose concentration in transgenic apple calli and mature fruit. Enzyme activity assays indicated that the overexpression of and enhanced sucrose phosphate synthase (SPS) activity in transgenic materials. RNA-seq and expression analysis showed that the expression levels of genes were up-regulated in -overexpressed apple fruit and -overexpressed apple calli. Further study showed that the inhibition of or expression in transgenic fruit could reduce or eliminate, respectively, the positive effect of on sucrose accumulation. Moreover, some starch cleavage-related genes (, , ) and the key gluconeogenesis-related phosphoenolpyruvate carboxykinase gene were significantly up-regulated in the transcriptome differentially expressed genes of mature fruit overexpressing . These results indicate that alteration of malate metabolism mediated by might regulate the expression of and SPS activity via affecting starch metabolism or gluconeogenesis, and thus accelerate sucrose synthesis and accumulation in fruit.
果实中可溶性糖和有机酸的种类及比例显著影响风味品质。然而，关于果实中有机酸与糖代谢之间的相互调控报道较少。在此，我们发现细胞质苹果酸脱氢酶基因（）的过表达不仅增加了转基因苹果愈伤组织和成熟果实中的苹果酸含量，还提高了蔗糖浓度。酶活性分析表明，和的过表达增强了转基因材料中蔗糖磷酸合酶（SPS）的活性。RNA测序和表达分析显示，基因的表达水平在过表达苹果果实和过表达苹果愈伤组织中上调。进一步研究表明，在转基因果实中抑制或的表达可分别降低或消除对蔗糖积累的积极作用。此外，一些与淀粉分解相关的基因（、、）和关键的糖异生相关磷酸烯醇式丙酮酸羧激酶基因在过表达成熟果实的转录组差异表达基因中显著上调。这些结果表明，介导的苹果酸代谢改变可能通过影响淀粉代谢或糖异生调节的表达和SPS活性，从而加速果实中蔗糖的合成与积累。
