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.
萜烯挥发物在植物与生物之间的相互作用中扮演着重要角色,作为吸引传粉者的引诱物或作为对抗草食动物的防御化合物。在最常见的植物挥发物中,同萜烯经常从夜间有香味的花朵和在草食动物攻击后从空气组织中散发出来。从草食动物受损组织释放的同萜烯挥发物被认为通过吸引害虫的天敌来促进植物的间接防御。此外,同萜烯已被证明能够诱导植物-植物相互作用中的防御反应。虽然同萜烯的生物合成早期步骤已经阐明,但直接形成这些挥发物的酶的身份仍然未知。在这里,我们证明了CYP82G1(At3g25180)是<斜体>拟南芥< /斜体> CYP82家族的细胞色素P450单加氧酶,负责将C 20 -前体(<斜体>E斜体>,<斜体>E斜体>)-香叶醇分解为昆虫诱导的C 16 -同萜烯(<斜体>E斜体>,<斜体>E斜体>)-4,8,12-三甲基十三碳烯-1,3,7,11-四烯。重组CYP82G1对(<斜体>E斜体>,<斜体>E斜体>)-香叶醇及其C 15 -类似物(<斜体>E斜体>)-内酯醇具有狭窄的底物特异性,后者转化为相应的C 11 -同萜烯(<斜体>E斜体>)-4,8-二甲基-1,3,7-壬三烯(DMNT)。基于同源建模和底物对接支持通过极性头的<斜体>syn< /斜体>-消除和联烯C-5氢原子的氧化键裂解酒精底物。<斜体>CYP82G1< /斜体>在<斜体>拟南芥< /斜体>茎和花序中具有固有表达,并与叶子中的香叶醇合成酶表现出高度协调的草食动物诱导表达,取决于F-box蛋白COI-1。CYP82G1代表了植物CYP82家族中具有DMNT / TMTT同萜烯合成酶功能的独特酶。