Induction of phenylalanine ammonia-lyase and lipoxygenase in cotton seedlings by mechanical wounding and aphid infestation

Plants have developed a multitude of inducibledefense mechanisms against aggressive biotic and abi otic agents1]. Wound and herbivory induced plantresponses can negatively affect herbivore’s physiologydirectly by stimulating the synthesis of toxic metabo lites2—4]. In addition to such direct defense mecha nisms, plants can also emit specific blends of volatilesthat attract carnivorous enemies to defend themselvesagainst herbivores5—9].Herbivory induced plant volatiles can n…

Induction of phenylalanine ammonia-lyase and lipoxygenase in cotton seedlings by mechanical wounding and aphid infestation

It has been suggested that infestation of plants causes increases in the activities of phenylalanine ammonia-lyase (PAL)and lipoxygenase (LOX), key enzymes in the phenolic compounds synthesis pathway and the octadecanoid pathway, respectively. The purpose of this work is to investigate whether the infestation of cotton aphid (Aphis gossypii ) and mechanical wound can cause the induction of PAL and LOX activities in cotton seedlings, and whether the induction occurs in healthy seedlings growing nearby the attacked ones. The specific activities of PAL and LOX were measured using spectrophotometric method after aphid infestation and mechanical wounding. Result indicated that PAL activity and LOX activity were greatly induced by mechanical wounding and aphid infestation in cotton seedlings. The induction of PAL and LOX occurred not only in wounded and infested seedlings but also in intact healthy seedlings growing nearby. After exposed to the aphid infestation-induced volatiles, the specific activity of PAL in cotton seedlings increased by 6 % at 24 h, 80 % at 48 h, 235 % at 72 h compared to the control, and the specific activity of LOX increased by 18 % at 24 h, 34 % at 48 h,24 % at 72 h, respectively. In comparison, the specific activity of PAL in unwounded seedlings exposed to wound-induced volatiles increased by 0.0 at 24 h, 200% at 48 h, 164% at 72 h, respectively and the specific activity of LOX increased by 28% at 24 h, 37% at 48 h, 8 % at 72 h, respectively. It suggests that the induced volatiles are involved in plant-plant communication as airborne transferred signals.