Hydroperoxide lyase and allene oxide synthase are differently induced and avoid competition for the same substrate.

Abstract

Plant oxylipins are formed from linolenic acid 13-hydroperoxide. The hydroperoxide is the common substrate for the jasmonate and hexenal pathways. Jasmonates and hexenals have distinct physiological functions, thus, the two branches must avoid competition of hydroperoxide lyase (HPL) and allene oxide synthase (AOS) for the same substrate to adjust the amounts of the end products appropriately. When pHPL::GUS and pAOS::GUS plants were analyzed, pHPL was active in the stigmas, filaments, and calyxes, while pAOS was active specifically in anthers. The activity of pHPL was extensively suppressed in coi1 mutant, thus, it was suggested that jasmonates were essential for the activation. When the leaves were mechanically wounded, high activity of pHPL could be found at the rim of leaves while that of pAOS could be found at the mid vein. Accordingly, tissue specific expression of these two enzymes might be one way to avoid competition for the same substrate.