Lipoxygenases and Their Function in Plant Innate Mechanism

Abstract

Lipoxygenases are universally distributed non-heme iron-containing dioxygenases, widely found in plants and animals. Lipoxygenases catalyzes the addition of an oxygen molecule to polyunsaturated fatty acids such as linoleic acid and linolenic acid. The syntheses of a group of acyclic or cyclic compounds collectively called oxylipins are initiated by LOX, which are products of fatty acid oxidation, with diverse functions in the cell. These oxylipins constitute a group of cyclic and acyclic compounds that coordinately amplify defense responses. Hydroperoxides transport calcium ions from outside to the inside of cell leading to activation of phospholipase A and release of polyunsaturated fatty acids from phospholipids of chloroplast membranes. These hydroperoxides are converted to oxylipins present in the chloroplast envelope by the allene oxide synthase or the hydroperoxide lyase. These phyto-oxylipins activate the gene expression resulting in a defense response against stress. Lipoxygenase pathway results in the production of traumatin, jasmonic acid, oxylipins, and volatile aldehydes that play an important role in wound healing, synthesis of antimicrobial substances in host–pathogen interactions, and membrane damage during the hypersensitive response.