Cytochrome P450-dependent metabolism of oxylipins in tomato. Cloning and expression of allene oxide synthase and fatty acid hydroperoxide lyase

Allene oxide synthase (AOS) and fatty acid hydroperoxide lyase (HPL) are pl ant-specific cytochrome P450s that commit fatty acid hydroperoxides to diff erent branches of oxylipin metabolism. Here we report the cloning and chara cterization 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-hydropero xide derivatives of C-18 fatty acids. LeAOS was active against both 13S-hyd roperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid (13-HPOT) and 13S-hydropero xy-9(Z),11(E)-octadecadienoic acid, whereas LeHPL showed a strong preferenc e for 13-HPOT. These results suggest a role for LeAOS and LeHPL in the meta bolism of 13-HPOT to jasmonic acid and hexenal/traumatin, respectively. LeA OS expression was detected in all organs of the plant. In contrast, LeHPL e xpression was predominant in leaves and flowers. Damage inflicted to leaves by chewing insect larvae led to an increase in the local and systemic expr ession of both genes, with LeAOS showing the strongest induction. Wound-ind uced expression of LeAOS also occurred in the def-l mutant that is deficien t in octadecanoid-based signaling of defensive proteinase inhibitor genes. These results demonstrate that tomato uses genetically distinct signaling p athways for the regulation of different classes of wound responsive genes.