Stilbenoid prenyltransferases define key steps in the diversification of peanut phytoalexins
Stilbenoid prenyltransferases define key steps in the diversification of peanut phytoalexins
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DOI：
10.1074/jbc.ra117.000564
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发表时间：
2017-11
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通讯作者：
Tianhong Yang;Lingling Fang;Sheri Sanders;S. Jayanthi;Gayathri Rajan;Ram Podicheti;S. Thallapuranam;K. Mockaitis;F. Medina-Bolivar
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作者：
Tianhong Yang;Lingling Fang;Sheri Sanders;S. Jayanthi;Gayathri Rajan;Ram Podicheti;S. Thallapuranam;K. Mockaitis;F. Medina-Bolivar
花生（Arachis hypogaea）对生物和非生物胁迫的防御反应包括异戊二烯化二苯乙烯类化合物的合成。这类化合物的成员在人类疾病研究中显示出几种保护活性，并且潜在治疗靶点的名单继续扩大。尽管它们在医学和生物学上的重要性，异戊二烯化芪类化合物的生物合成途径仍有待阐明，并且编码芪类化合物特异性异戊二烯基转移酶的基因尚未在任何植物物种中鉴定。在这项研究中，我们结合有针对性的转录组学和代谢组学分析，发现异戊烯基转移酶基因在激发子处理的花生毛状根培养。转录本编码五种酶进行了鉴定，其中两个功能的特点是在一个瞬时表达系统组成的根癌农杆菌渗透叶本氏烟草。我们观察到这些异戊烯基转移酶之一AhR 4DT-1催化异戊烯化芪类化合物生物合成中的关键反应，其中白藜芦醇在其C-4位被异戊烯化形成花生素-2，而另一个AhR 3 ′DT-1将异戊烯基添加到白藜芦醇的C-3′。这些异戊二烯基转移酶是高度特异性的芪类底物，我们证实了它们的亚细胞位置的质体荧光显微镜。异戊二烯化芪类化合物的结构分析表明，这两个异戊二烯基转移酶的活动代表了第一个承诺的步骤，在生物合成的大量异戊二烯化芪类化合物及其衍生物在花生。总之，我们已经确定了五个候选的异戊二烯基转移酶在花生和证实，其中两个是芪类化合物的具体，推进我们的理解，这个专门的酶家族和脱落关键光生物活性芪类化合物的生物合成。
Defense responses of peanut (Arachis hypogaea) to biotic and abiotic stresses include the synthesis of prenylated stilbenoids. Members of this compound class show several protective activities in human disease studies, and the list of potential therapeutic targets continues to expand. Despite their medical and biological importance, the biosynthetic pathways of prenylated stilbenoids remain to be elucidated, and the genes encoding stilbenoid-specific prenyltransferases have yet to be identified in any plant species. In this study, we combined targeted transcriptomic and metabolomic analyses to discover prenyltransferase genes in elicitor-treated peanut hairy root cultures. Transcripts encoding five enzymes were identified, and two of these were functionally characterized in a transient expression system consisting of Agrobacterium-infiltrated leaves of Nicotiana benthamiana. We observed that one of these prenyltransferases, AhR4DT-1, catalyzes a key reaction in the biosynthesis of prenylated stilbenoids, in which resveratrol is prenylated at its C-4 position to form arachidin-2, whereas another, AhR3′DT-1, added the prenyl group to C-3′ of resveratrol. Each of these prenyltransferases was highly specific for stilbenoid substrates, and we confirmed their subcellular location in the plastid by fluorescence microscopy. Structural analysis of the prenylated stilbenoids suggested that these two prenyltransferase activities represent the first committed steps in the biosynthesis of a large number of prenylated stilbenoids and their derivatives in peanut. In summary, we have identified five candidate prenyltransferases in peanut and confirmed that two of them are stilbenoid-specific, advancing our understanding of this specialized enzyme family and shedding critical light onto the biosynthesis of bioactive stilbenoids.