Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, No. 151, Malianwa North Road, Haidian District, Beijing 100193, China.
Basic Medical School, Jiangxi University of Traditional Chinese Medicine, Xingwan Road 818, Nanchang, Jiangx, 330004, China.
Plant Cell Physiol. 2017 Nov 1;58(11):1924-1933. doi: 10.1093/pcp/pcx122.
Sesquiterpenes are one of the most important defensive secondary metabolite components of agarwood. Agarwood, which is a product of the Aquilaria sinensis response to external damage, is a fragrant and resinous wood that is widely used in traditional medicines, incense and perfume. We previously reported that jasmonic acid (JA) plays an important role in promoting agarwood sesquiterpene biosynthesis and induces expression of the sesquiterpene synthase ASS1, which is a key enzyme that is responsible for the biosynthesis of agarwood sesquiterpenes in A. sinensis. However, little is known about this molecular regulation mechanism. Here, we characterized a basic helix-loop-helix transcription factor, AsMYC2, from A. sinensis as an activator of ASS1 expression. AsMYC2 is an immediate-early jasmonate-responsive gene and is co-induced with ASS1. Using a combination of yeast one-hybrid assays and chromatin immunoprecipitation analyses, we showed that AsMYC2 bound the promoter of ASS1 containing a G-box motif. AsMYC2 activated expression of ASS1 in tobacco epidermis cells and up-regulated expression of sesquiterpene synthase genes (TPS21 and TPS11) in Arabidopsis, which was also promoted by methyl jasmonate. Our results suggest that AsMYC2 participates in the regulation of agarwood sesquiterpene biosynthesis in A. sinensis by controlling the expression of ASS1 through the JA signaling pathway.
倍半萜是沉香防御性次生代谢物的重要组成部分之一。沉香是由白木香树对外部损伤的反应而产生的一种芳香树脂木材，广泛应用于传统药物、香薰和香水。我们之前报道过茉莉酸（JA）在促进沉香倍半萜生物合成中起着重要作用，并诱导倍半萜合酶 ASS1 的表达，ASS1 是负责沉香中倍半萜生物合成的关键酶。然而，目前对于这个分子调控机制还知之甚少。在这里，我们鉴定了一个来自白木香的碱性螺旋-环-螺旋转录因子 AsMYC2，它是 ASS1 表达的激活子。AsMYC2 是一个即时早期的茉莉酸响应基因，与 ASS1 共同诱导表达。通过酵母单杂交实验和染色质免疫沉淀分析，我们表明 AsMYC2 结合 ASS1 启动子，该启动子含有 G 盒基序。AsMYC2 在烟草表皮细胞中激活 ASS1 的表达，并上调拟南芥中倍半萜合酶基因（TPS21 和 TPS11）的表达，茉莉甲酯也能促进其表达。我们的结果表明，AsMYC2 通过 JA 信号通路控制 ASS1 的表达，参与了沉香中倍半萜生物合成的调控。
