Piirtola Eerik-Mikael, Ma Dawei, Ehlting Jürgen, Constabel C Peter
Centre for Forest Biology & Department of Biology, University of Victoria, 3800 Finnerty Road, Victoria, British Columbia, V8P 5C2Canada.
J Exp Bot. 2025 May 27;76(8):2129-2143. doi: 10.1093/jxb/eraf020.
Production of secreted leaf bud resin is a mechanism for temperate trees to protect dormant leaf buds against frost damage, dehydration, and insect herbivory. Bud resins contain a wide variety of special metabolites including terpenoids, benzenoids, and phenolics. The leaf bud resins of Populus trichocarpa and P. balsamifera contain high concentrations of O-methylated dihydrochalcones, but the enzymes for methylating these compounds remain enigmatic. We used transcriptomics and differential gene expression analyses to identify a gene encoding a P. trichocarpa dihydrochalcone-specific O-methyltransferase, which we named PtDOMT1. Detailed enzymatic analyses demonstrated PtDOMT1 to be a highly selective and regiospecific O-methyltransferase which methylates 4 and 4' positions of dihydrochalcones using S-adenosyl-l-methionine as a methyl donor. PtDOMT1 did not methylate any other flavonoid or phenolic substrate tested. These findings establish the final step in the biosynthesis of O-methylated dihydrochalcones in poplar and represent the first molecular analysis of leaf bud resin biosynthesis in plants.
分泌型叶芽树脂的产生是温带树木保护休眠叶芽免受冻害、脱水和昆虫食草作用的一种机制。芽树脂含有多种特殊代谢产物，包括萜类、苯类和酚类。毛果杨和香脂杨的叶芽树脂含有高浓度的O-甲基化二氢查耳酮，但甲基化这些化合物的酶仍然未知。我们利用转录组学和差异基因表达分析，鉴定出一个编码毛果杨二氢查耳酮特异性O-甲基转移酶的基因，我们将其命名为PtDOMT1。详细的酶学分析表明，PtDOMT1是一种高度选择性和区域特异性的O-甲基转移酶，它以S-腺苷-L-甲硫氨酸作为甲基供体，甲基化二氢查耳酮的4位和4'位。PtDOMT1不会甲基化所测试的任何其他类黄酮或酚类底物。这些发现确定了杨树中O-甲基化二氢查耳酮生物合成的最后一步，并代表了植物中叶芽树脂生物合成的首次分子分析。
