UGT74B5-mediated glucosylation at ortho hydroxyl groups of benzoic acid derivatives regulating plant immunity to anthracnose in tea plants

Abstract

Benzoates, particularly salicylic acid (SA) and its derivatives, play critical roles in plant immune responses and basal defense through hydroxylation and glycosylation. Anthracnose is one of the most common and devastating diseases in tea plants (Camellia sinensis). However, the role of SA and its derivatives in tea plant immunity and resistance to anthracnose remains largely unexplored. In the present study, we identified and characterized a glycosyltransferase, CsUGT74B5, which was significantly downregulated in tea seedlings upon anthracnose infection. CsUGT74B5 was preferentially expressed in mature leaves and stem, and responded rapidly to exogenous SA treatment. Phylogenetic analysis suggested CsUGT74B5 might possess the catalytic activity toward benzoates. Enzymatic assays and molecular docking demonstrated recombinant CsUGT74B5 specifically glycosylated at the ortho hydroxyl groups of SA and 2, 6-dihydroxybenzoic acid (2, 6-DHBA), but did not glycosylate 2, 3-DHBA, 2, 5-DHBA, or other substrates in vitro. Overexpression of CsUGT74B5 in Arabidopsis thaliana and tobacco (Nicotiana tabacum) reduced SA level while promoting the accumulation of SA 2-O-β-D-glucoside (SAG), further validating the in vivo function of CsUGT74B5. Moreover, transient overexpression of CsUGT74B5 in two tea plant cultivars increased their sensitivity to anthracnose and accelerated lesion development, which was attributed to decreased SA levels. Overall, our finding demonstrated that CsUGT74B5-mediated biosynthesis of SAG regulated tea plant immunity against anthracnose by fine-tuning free SA levels, providing new progress into the immunity response of tea plants.

Acknowledgements

This work was supported by the Youth Innovation and Science Technology Support Program (2021KJ103), Natural Science Foundation of China (32272775, 32372764), Natural Science Foundation of Shandong province (ZR2022MC088), and Technology System of Modern Agricultural Industry in Shandong Province (SDAIT-19-00).

Author contributions

P.W. and L.Z. conceived and designed the experiment with the help of L.G. and T.X. C.L. and F.W. performed most of the experiments, validation, and drafting of the preliminary draft. N.L. did the genetic transformation of A. thaliana and the qRT-PCR experiments. L.Y. helped do the enzyme activity experiment of CsUGT74B5 in vitro. X.Z. and F.Q. reviewed and helped modify the language of the article. All authors had read and agreed to the published version of the manuscript.

Data availability

The data that support the findings of this manuscript are available in the article and the supplementary Tables and Figures. The transcriptome data had been uploaded to the Sequence Read Archive database on NCBI with the accession number of PRJNA857833.

Conflict of interest statement

The authors declare that they have no conflict of interest.

Supplementary Data

Supplementary data is available at Horticulture Research online.

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