Response to wound-activated stress through a lipid oxidative metabolic pathway in Pyropia haitanensis

Abstract

Pyropia haitanensis inhabits the intertidal zone and is affected by rough waves and sediment, as well as herbivore-induced and mechanical damage. However, the mechanisms of P. haitanensis response to wounding have not been elucidated. Lipid metabolism is an important defense mechanism in algae, and the lipid defense strategy of P. haitanensis elicited by wound-activated stress was investigated in this study. P. haitanensis was damaged by cutting and allowed to recover for 30 and 60 min. Release of H2O2 that was stimulated by wounding could act as a primary signal to induce phospholipase A2 activation, which catalyzes the degradation of membrane lipids to release free fatty acids. Then, several polyunsaturated fatty acids (C18:2, C20:4 and C20:5) were oxidized by PhLOXs, resulting in decreased polyunsaturated fatty acid levels and increased oxylipins, which were further transformed into short-chain volatile organic compounds. Moreover, increased jasmonic acid levels were also detected after wounding, indicating that the jasmonic acid pathway may also be involved in the defense response of P. haitanensis to wounding, similar to higher plants. Hence, the oxidative lipid metabolic pathway elucidated herein offers plausible physiological insights into lipid metabolism in P. haitanensis in response to wound-activated stress and may facilitate efficient development and improvement of Pyropia quality by producing cultivars resistant to wounding.