Functional Characterization of the Methyl Esterase MES4 in Hydrolytic Activity of Methylated Phytohormones in Tea Plants Based on Multi-Omics Analysis

This
study integrated transcriptome and hormone profiling of Colletotrichum camelliae-infected tea leaves to identify
the methyl esterase (MES) gene family.
Genome-wide analysis identified 17 MES genes, with CsMES4 as a crucial candidate localized in the nucleus and
cell membrane. Through prokaryotic expression, purification, in vitro
enzymatic assays, and transient silencing experiments in tea plants,
we demonstrated that CsMES4 hydrolyze methyl salicylate (MeSA), methyl
indole-3-acetate (MeIAA), and methyl jasmonate (MeJA) to produce salicylic
acid, indole-3-acetic acid, and jasmonic acid, respectively. Transient
silencing of CsMES4 reduced these hormones and enlarged
lesions, confirming its role in disease resistance. Key catalytic
residues predicted by docking were validated by mutagenesis: the F60L
mutation significantly decreased CsMES4’s catalytic activity
toward all three substrates, while the S127Y mutation enhanced its
catalytic efficiency. This study highlights the pivotal role of CsMES4
in phytohormone metabolism and provides insights into its multifunctional
catalytic mechanism in tea plants.