UDP-glycosyltransferase PpUGT74F2 is involved in fruit immunity via modulating salicylic acid metabolism

Abstract

Flesh fruits are essential for human health, but pathogen infection poses a threat to fruit production and postharvest storage. The hormone salicylic acid (SA) and its metabolites, such as sugar conjugates and methyl salicylate (MeSA), play a crucial role in regulating plant immune responses. However, the UDP-glycosyltransferases (UGTs) responsible for modulating SA metabolism in fruit have yet to be identified, and further investigation is needed to elucidate its involvement in fruit immune response. Here, we identified PpUGT74F2 as an enzyme with the highest transcription level in peach fruit, responsible for catalyzing the biosynthesis of SA glucoside (SAG), but not for MeSAG formation in fruit. Furthermore, infection of peach fruit with Monilinia fructicola, which causes brown rot disease, led to reduced expression of PpUGT74F2, resulting in a significant decrease in SAG content and an increase in MeSA levels. Transgenic tomatoes expressing heterologous PpUGT74F2 increased susceptibility to gray mold. Interestingly, overexpressing PpUGT74F2 did not affect SA levels but dramatically reduced MeSA levels in response to pathogen infection, accompanied by significantly reduced expression of pathogen-related (PR) genes in transgenic tomatoes. This study highlights that PpUGT74F2 acts as a negative regulatory factor for fruit immunity through a distinct mechanism not previously reported in plants.

Acknowledgements

This work was supported by Zhejiang Provincial Natural Science Foundation (LD22C150001) and Ningbo Key Research and Development Program (2022Z179). We want to thank Zhongjing Zhou (Central Laboratory, State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Zhejiang Academy of Agricultural Sciences) for the technical support in UPLC-QqQ-MS/MS analysis.

Author contributions

B.Z., B.W., and D.J. designed the experiments. D.J. performed most of the experiments and data analysis. S.L. participated in the experiment of peach fruit treatment. L.X. and B.W. detected the enzyme activity of recombinant proteins. M.C. and Y.S. took care of plants and provided fruit for analysis, K.C. and X.L. provided experimental instruments. B.W., D.J., and B.Z. prepared the manuscript. All authors have read and approved the final manuscript.

Data availability

RNA-Seq raw data can be found in the NCBI with accession number PRJNA576753 for peach samples at different development and ripening stages.

Conflict of interest statement

The authors declare no competing interests.

Supplementary data

Supplementary data is available at Horticulture Research online.

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