TEMPORAL AND ONTOGENIC ASPECTS OF PROTEIN INDUCTION IN FOLIAGE OF THETOMATO, LYCOPERSICON-ESCULENTUM

Damage to foliage of the tomato, Lycopersicon esculentum, causes the i nduction of proteinase inhibitors and of the oxidative enzymes polyphe nol oxidase. peroxidase, and lipoxygenase. The time courses of inducti on of these proteins by feeding of two caterpillar species (Manduca se xta and Heli-coverpa zee) were studied in a series of experiments. In another series of experiments, the effects of plant age on the inducib ility of these proteins were studied. In the time course experiments, induction of proteinase inhibitors and oxidative enzymes in the damage d leaflet was rapid, with higher protein activities evident in damaged leaflets within 12-24 h of damage, depending on the enzyme and the sp ecies of insect used to damage the plant. Systemic induction of protei nase inhibitors was also rapid. but systemic induction of polyphenol o xidase was delayed relative to systemic induction of proteinase inhibi tors, possibly because high constitutive polyphenol oxidase activities obscured expression of systemic induction at earlier time points. Lip oxygenase and peroxidase were not induced systemically. Induction of a ll proteins persisted for at least 21 days. In the phenology experimen ts, inducibility of all proteins decreased in magnitude and was less c onsistent as plants aged. The results of these experiments exemplify t he numerous constraints on induction in tomato plants. Knowledge of th ese physiological constraints is important to an understanding of the ecological role and causal basis of induced resistance. Copyright (C) 1996 Elsevier Science Ltd