Herbivore Response in Passion Fruit (Passiflora edulis Sims) Plants: Induction of Lipoxygenase Activity in Leaf Tissue in Response to Generalist and Specialist Insect Attack

Lipoxygenases (LOXs, EC 1.13.11.12) are a class of non-heme iron containing dioxygenases which catalyze the regiospecific and stereospecific hydroperoxidation of polyunsaturated fatty acids with 1,4-pentadiene system such as linoleic acid and linolenic acid in plants. In this work we studied the LOX activity in damaged as well as in distal leaves in response to specialist (Agraulis vanillae vanillae) or generalist (Spodoptera frugiperda) insect attack. Enzymatic assays showed that induction of LOX activity occurred locally and systemically in response to both insects' attacks. Northern blot analysis revealed that LOX expression is also insect-inducible in agreement with enzymatic assay results. In addition, northern analysis corroborated previous reports that LOX activity is wound-and methyl jasmonate-inducible. These results suggest that the herbivore-response in passion fruit is mediated by jasmonates, since a key enzyme of the biosynthetic pathway of jasmonic acid is induced upon lepidopteran insects' attacks.