The plant U-box E3 ubiquitin ligases-mediated ubiquitin/26S proteasome degradation system plays a key role in plant growth and development. Previously screened from the grape PUB gene family, PUB38 was shown to participate in the berry ripening progress. Here, we demonstrate 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 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 26S proteasome system. These results indicate VlPUB38 negatively regulates grape fruit ripening by mediating the degradation of key factor VlAAO in the ABA synthesis pathway.

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