Abstract

The plant U-box E3 ubiquitin ligase-mediated ubiquitin/26S proteasome degradation system plays a key role in plant growth and development. Previously identified as a member of the grape PUB gene family, PUB38 was shown to participate in the berry-ripening progress. Here, we demonstrate that the E3 ligase VlPUB38 mediates abscisic acid (ABA) synthesis via 26S proteasome degradation and its involvement in regulating fruit-ripening processes. Strawberry-overexpressing VlPUB38 lines displayed obvious inhibition of mature phenotype, and this was rescued by exogenous ABA treatment and MG132. Post-ABA treatment, expression levels of ABA response-related genes in VlPUB38-overexpressed Arabidopsis significantly exceeded controls. Strawberry and Arabidopsis ectopic expression assays suggest that VlPUB38 negatively regulates fruit ripening in an ABA-dependent manner. Moreover, VlPUB38 has ubiquitin ligase activity, which depends on the U-box-conserved domain. VlPUB38 interacts with abscisic-aldehyde oxidase (VlAAO), targeting VlAAO proteolysis via the 26S proteasome system. These results indicate that VlPUB38 negatively regulates grape fruit ripening by mediating the degradation of key factor VlAAO in the ABA synthesis pathway.

中文翻译：

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葡萄U-Box E3泛素连接酶VlPUB38通过促进脱落酸醛氧化酶的降解来负调控果实的成熟

摘要

植物U-box E3泛素连接酶介导的泛素/ 26S蛋白酶体降解系统在植物生长发育中起关键作用。PUB38先前被鉴定为葡萄PUB基因家族的成员，被证明参与了浆果成熟过程。在这里，我们证明了E3连接酶V1PUB38通过26S蛋白酶体降解及其参与调节果实成熟过程而介导了脱落酸（ABA）的合成。草莓过表达的V1PUB38品系表现出明显的成熟表型抑制作用，这通过外源ABA处理和MG132得以挽救。ABA处理后，VlPUB38中ABA反应相关基因的表达水平-过表达的拟南芥明显超过对照。草莓和拟南芥异位表达测定表明，V1PUB38以ABA依赖性方式负面调节果实成熟。此外，V1PUB38具有泛素连接酶活性，其依赖于U盒保守的结构域。V1PUB38与脱落醛氧化酶（V1AAO）相互作用，靶向经由26S蛋白酶体系统的V1AAO蛋白水解。这些结果表明，V1PUB38通过介导ABA合成途径中关键因子V1AAO的降解而负调节葡萄果实的成熟。