Herbivore-induced and floral homoterpene volatiles are biosynthesized by a single P450 enzyme (CYP82G1) in Arabidopsis
Herbivore-induced and floral homoterpene volatiles are biosynthesized by a single P450 enzyme (CYP82G1) in Arabidopsis
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DOI：
10.1073/pnas.1009975107
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发表时间：
2010-12-07
影响因子：
11.1
通讯作者：
Tholl, Dorothea
中科院分区：
文献类型：
--
作者：
Lee, Sungbeom;Badieyan, Somayesadat;Tholl, Dorothea
萜类挥发物在植物与生物的相互作用中起着重要的作用，可以作为传粉媒介的吸引剂或对食草动物的防御化合物。在最常见的植物挥发物中是同型萜烯，它经常从夜花和草食动物攻击时的空中组织中释放出来。从食草动物受损的组织中释放的同型萜挥发物被认为通过吸引害虫的天敌来间接防御植物。此外，同型萜烯已被证明在植物-植物相互作用中诱导防御反应。虽然在同型萜的生物合成的早期步骤已经阐明，负责直接形成这些挥发物的酶的身份仍然是未知的。在这里，我们证明CYP82G1 （At3g25180）是拟南芥CYP82家族的细胞色素P450单加氧酶，负责将c -20前体（E， E）-香叶芳樟醇分解为昆虫诱导的c -16-同萜类（E， E）-4,8,12-三甲基三萜-1,3,7,11-四烯（TMTT）。重组CYP82G1对（E， E）香叶樟醇及其c -15类似物(E)-神经醇具有较窄的底物特异性，它们分别转化为c -11-同源萜烯(E)-4,8-二甲基-1,3,7-非atriene （DMNT）。基于同源性的建模和底物对接通过消去极性头和烯丙基C-5氢原子，支持醇底物的氧化键裂解。CYP82G1在拟南芥茎和花序中组成性表达，并通过F-box蛋白COI-1在叶片中与香叶醛合成酶高度协调地表达。CYP82G1是植物CYP82家族中一种独特的酶，具有DMNT/TMTT同型萜烯合成酶的功能。
Terpene volatiles play important roles in plant-organism interactions as attractants of pollinators or as defense compounds against herbivores. Among the most common plant volatiles are homoterpenes, which are often emitted from night-scented flowers and from aerial tissues upon herbivore attack. Homoterpene volatiles released from herbivore-damaged tissue are thought to contribute to indirect plant defense by attracting natural enemies of pests. Moreover, homoterpenes have been demonstrated to induce defensive responses in plant-plant interaction. Although early steps in the biosynthesis of homoterpenes have been elucidated, the identity of the enzyme responsible for the direct formation of these volatiles has remained unknown. Here, we demonstrate that CYP82G1 (At3g25180), a cytochrome P450 monooxygenase of the Arabidopsis CYP82 family, is responsible for the breakdown of the C-20-precursor (E, E)-geranyllinalool to the insect-induced C-16-homoterpene (E, E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT). Recombinant CYP82G1 shows narrow substrate specificity for (E, E)geranyllinalool and its C-15-analog (E)-nerolidol, which is converted to the respective C-11-homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). Homology-based modeling and substrate docking support an oxidative bond cleavage of the alcohol substrate via syn-elimination of the polar head, together with an allylic C-5 hydrogen atom. CYP82G1 is constitutively expressed in Arabidopsis stems and inflorescences and shows highly coordinated herbivore-induced expression with geranyllinalool synthase in leaves depending on the F-box protein COI-1. CYP82G1 represents a unique characterized enzyme in the plant CYP82 family with a function as a DMNT/TMTT homoterpene synthase.