Howe G A, Lee G I, Itoh A, Li L, DeRocher A E
Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing 48824, USA.
Plant Physiol. 2000 Jun;123(2):711-24. doi: 10.1104/pp.123.2.711.
Allene oxide synthase (AOS) and fatty acid hydroperoxide lyase (HPL) are plant-specific cytochrome P450s that commit fatty acid hydroperoxides to different branches of oxylipin metabolism. Here we report the cloning and characterization of AOS (LeAOS) and HPL (LeHPL) cDNAs from tomato (Lycopersicon esculentum). Functional expression of the cDNAs in Escherichia coli showed that LeAOS and LeHPL encode enzymes that metabolize 13- but not 9-hydroperoxide derivatives of C(18) fatty acids. LeAOS was active against both 13S-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid (13-HPOT) and 13S-hydroperoxy-9(Z),11(E)-octadecadienoic acid, whereas LeHPL showed a strong preference for 13-HPOT. These results suggest a role for LeAOS and LeHPL in the metabolism of 13-HPOT to jasmonic acid and hexenal/traumatin, respectively. LeAOS expression was detected in all organs of the plant. In contrast, LeHPL expression was predominant in leaves and flowers. Damage inflicted to leaves by chewing insect larvae led to an increase in the local and systemic expression of both genes, with LeAOS showing the strongest induction. Wound-induced expression of LeAOS also occurred in the def-1 mutant that is deficient in octadecanoid-based signaling of defensive proteinase inhibitor genes. These results demonstrate that tomato uses genetically distinct signaling pathways for the regulation of different classes of wound responsive genes.
丙二烯氧化物合酶（AOS）和脂肪酸氢过氧化物裂解酶（HPL）是植物特有的细胞色素P450，它们使脂肪酸氢过氧化物进入脂氧合产物代谢的不同分支。本文我们报道了来自番茄（Lycopersicon esculentum）的AOS（LeAOS）和HPL（LeHPL）cDNA的克隆及特性分析。这些cDNA在大肠杆菌中的功能表达表明，LeAOS和LeHPL编码的酶可代谢C(18)脂肪酸的13-氢过氧化物衍生物而非9-氢过氧化物衍生物。LeAOS对13S-氢过氧-9(Z),11(E),15(Z)-十八碳三烯酸（13-HPOT）和13S-氢过氧-9(Z),11(E)-十八碳二烯酸均有活性，而LeHPL对13-HPOT表现出强烈偏好。这些结果表明LeAOS和LeHPL分别在13-HPOT代谢生成茉莉酸和己醛/创伤激素的过程中发挥作用。在植物的所有器官中均检测到LeAOS的表达。相比之下，LeHPL的表达在叶和花中占主导。咀嚼式昆虫幼虫对叶片造成的损伤导致这两个基因在局部和整体的表达均增加，其中LeAOS的诱导作用最强。LeAOS的创伤诱导表达也发生在def-1突变体中，该突变体在基于十八烷酸的防御蛋白酶抑制剂基因信号传导方面存在缺陷。这些结果表明，番茄利用遗传上不同的信号通路来调控不同类别的创伤响应基因。
