Bai Qian, Chen Xuexue, Zheng Zhenzhen, Feng Jinjing, Zhang Yanjun, Shen Yuanyue, Huang Yun
Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
Ministry of Education Key Laboratory of Silviculture and Conservation, College of Forestry, Beijing Forestry University, 35 East Qinghua Road, Beijing 100083, China.
Hortic Res. 2022 Nov 22;10(2):uhac260. doi: 10.1093/hr/uhac260. eCollection 2023 Feb.
Vacuolar Phosphate Transporter1 (VPT1)-mediated phosphate uptake in the vacuoles is essential to plant development and fruit ripening. Interestingly, here we find that the VPT1 may transport sugar in response to soluble sugar status of fruits. The VvVPT1 protein isolated from grape () berries was tonoplast-localized and contains SPX (Syg1/Pho81/XPR1) and MFS (major facilitator superfamily) domains. Its mRNA expression was significantly increased during fruit ripening and induced by sucrose. Functional analyses based on transient transgenic systems in grape berry showed that VvVPT1 positively regulated berry ripening and significantly affected hexose contents, fruit firmness, and ripening-related gene expression. The VPT1 proteins (Grape VvVPT1, strawberry FaVPT1, and Arabidopsis AtVPT1) all showed low affinity for phosphate verified in yeast system, while they appear different in sugar transport capacity, consistent with fruit sugar status. Thus, our findings reveal a role for VPT1 in fruit ripening, associated to its SPX and MFS domains in direct transport of soluble sugar available into the vacuole, and open potential avenues for genetic improvement in fleshy fruit.
液泡磷酸盐转运蛋白1（VPT1）介导的液泡对磷酸盐的吸收对植物发育和果实成熟至关重要。有趣的是，我们在此发现VPT1可能会根据果实的可溶性糖状态转运糖分。从葡萄浆果中分离出的VvVPT1蛋白定位于液泡膜，包含SPX（Syg1/Pho81/XPR1）和MFS（主要转运子超家族）结构域。其mRNA表达在果实成熟过程中显著增加，并受蔗糖诱导。基于葡萄浆果瞬时转基因系统的功能分析表明，VvVPT1正向调控浆果成熟，并显著影响己糖含量、果实硬度和成熟相关基因的表达。在酵母系统中验证，VPT1蛋白（葡萄VvVPT1、草莓FaVPT1和拟南芥AtVPT1）对磷酸盐均表现出低亲和力，而它们在糖分运输能力方面存在差异，这与果实糖分状态一致。因此，我们的研究结果揭示了VPT1在果实成熟中的作用，这与其SPX和MFS结构域在将可用可溶性糖直接转运到液泡中的功能相关，并为肉质果实的遗传改良开辟了潜在途径。
