PharmaQAM, Département de Chimie, Université du Québec à Montréal, C.P. 8888, Succursale Centre-ville, Montréal, Québec H3C 3P8, Canada.
Plant Sci. 2013 Mar;201-202:115-20. doi: 10.1016/j.plantsci.2012.12.005. Epub 2012 Dec 13.
In plants, O-methylation is mediated by an enzyme family of O-methyltransferases (OMTs) that transfer the methyl groups from the methyl donor, S-adenosyl-L-methionine (AdoMet) to suitable phenolic acceptor molecules. In a previous study [1], a flavonoid OMT (TaOMT2) was isolated and characterized from wheat (Triticum aestivum L.) leaves. Its novel gene product catalyzes three sequential O-methylations of the flavone tricetin (5,7,3',4',5'-pentahydroxyflavone) to its 3'-monomethyl-(selgin)→3',5'-dimethyl-(tricin)→3',4',5'-trimethyl (TMT) ether derivatives, with tricin being the major product of the reaction. In this report, the biological significance of tricetin methylation was investigated by measuring the OMT activity, its expression level, and the accumulation of its major product (tricin) at different stages of development of wheat plants exposed to different abiotic stresses such as cold, salt and drought. The results showed that tricin accumulates mostly in wheat inflorescences under normal conditions compared to leaves and other developmental stages. Tricin accumulation was associated with increased TaOMT2 expression level and its enzyme activity, suggesting a possible de novo synthesis of the enzyme at this important developmental stage. This phenomenon may be attributed to the putative role of tricin in protecting seeds against biotic and abiotic stresses. The functions of tricin during growth and development of wheat and the importance of tricetin methylation during abiotic stresses are discussed.
在植物中，O-甲基化是由一类 O-甲基转移酶（OMTs）家族介导的，这些酶将甲基基团从甲基供体 S-腺苷甲硫氨酸（AdoMet）转移到合适的酚类受体分子上。在之前的一项研究中[1]，从小麦（Triticum aestivum L.）叶片中分离并鉴定了一种类黄酮 OMT（TaOMT2）。其新颖的基因产物催化黄酮三槲皮素（5,7,3',4',5'-五羟基黄酮）的三个连续 O-甲基化，生成 3'-单甲基-（selgin）→3',5'-二甲基-（tricin）→3',4',5'-三甲基（TMT）醚衍生物，其中三槲皮素是反应的主要产物。在本报告中，通过测量小麦植株在不同非生物胁迫（如冷、盐和干旱）下不同发育阶段的 OMT 活性、表达水平及其主要产物（三槲皮素）的积累，研究了三槲皮素甲基化的生物学意义。结果表明，与叶片和其他发育阶段相比，在正常条件下，三槲皮素主要积累在小麦花序中。三槲皮素的积累与 TaOMT2 表达水平及其酶活性的增加有关，表明在这个重要的发育阶段可能存在该酶的从头合成。这种现象可能归因于三槲皮素在保护种子免受生物和非生物胁迫方面的潜在作用。讨论了三槲皮素在小麦生长发育中的功能以及三槲皮素甲基化在非生物胁迫中的重要性。
