Hydrolysable tannins (HTs) are useful secondary metabolites that are responsible for pharmacological activities and astringent taste, flavor, and quality in fruits. They are also the main polyphenols in Canarium album L. (Chinese olive) fruit, an interesting and functional fruit that has been cultivated for over 2000 years. The HT content of C. album fruit was 2.3–13 times higher than that of berries with a higher content of HT. 1-galloyl-β-d-glucose (βG) is the first intermediate and the key metabolite in the HT biosynthesis pathway. It is catalyzed by UDP-glucosyltransferases (UGTs), which are responsible for the glycosylation of gallic acid (GA) to form βG. Here, we first reported 140 UGTs in C. album. Phylogenetic analysis clustered them into 14 phylogenetic groups (A, B, D–M, P, and Q), which are different from the 14 typical major groups (A~N) of Arabidopsis thaliana. Expression pattern and correlation analysis showed that UGT84A77 (Isoform0117852) was highly expressed and had a positive correlation with GA and βG content. Prokaryotic expression showed that UGT84A77 could catalyze GA to form βG. These results provide a theoretical basis on UGTs in C. album, which will be helpful for further functional research and availability on HTs and polyphenols.

Valsa canker, caused by Valsa pyri (Vp), severely threatens global pear production. The VAMP72 family modulates plant immunity, but its role in Valsa canker resistance remains unclear. In this study, it was found that PbeVAMP724, encoding a membrane-localized SNARE protein, was significantly induced by Vp infection and Abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA) in the resistant pear rootstock Pyrus betulaefolia. Transient overexpression of PbeVAMP724 in ‘Huangguan’ fruits reduced Vp-induced lesions, and the lesion diameter was reduced by 23.1% at 48 h and 20.0% at 72 h compared to the empty vector control (pFGC-5941), whereas VIGS silencing compromised the resistance. Stable overexpression in suspension cells ‘Duli-G03’ (P. betulifolia) enhanced tolerance to Vp metabolites (VpM), alleviated cell death, and induced ROS bursts and defense responses. Weighted gene co-expression network analysis (WGCNA) revealed that phloem/xylem histogenesis-related genes (GWHGAAYT028948, GWHGAAYT039435) are co-expressed with PbeVAMP724. In conclusion, we demonstrate that PbeVAMP724 integrates hormone signaling, triggers ROS bursts, and activates defense responses to positively regulate resistance to Valsa canker in pear, representing a promising candidate for breeding Valsa canker-resistant pear varieties.