Abstract

In plants, lipoxygenase (LOX) and polyphenol oxidase (PPO) have been related to defense mechanisms against insect feeding and wounding and these roles were investigated in poplar (Populus simonii × Populus nigra) regarding induction by third-instar Lymantria dispar larvae feeding and punching mechanical wounding.The results showed that L. dispar feeding and mechanical wounding caused different responses of protein and transcript levels of LOX and PPO. PPO was obviously induced by L. dispar feeding during a 72 h period, while LOX was not significantly induced by L. dispar feeding. For mechanical wounding, activity and mRNA expression level of LOX and PPO were not significantly induced but were mostly inhibited. Therefore, LOX was not involved in defensive mechanisms of P. simonii × P. nigra. The PPO gene may be significantly related to poplar defense against L. dispar attack.

Key words: Lipoxygenase, polyphenol oxidase, Populus simonii × Populus nigra,Lymantria dispar feeding, mechanical wounding.