Overexpression of tobacco hydroxyproline-rich glycopeptide systemin precursor A gene in transgenic tobacco enhances resistance against Helicoverpa armigera larvae

Two tobacco hydroxyproline-rich glycopeptide systemin precursor proteins (TobpreproHypSys-A and -B) have been discovered recently. The TobpreproHypSys-A, from which TobHypSys I and TobHypSys II were released, has been reported to be induced by mechanical and herbivorous wounding systemically. Here our experiments by overexpressing TobpreproHypSys-A in transgenic plants indicated the overexpression of TobpreproHypSys-A enhances the resistance against Helicoverpa armigera larvae. The growth and development of H. armigera larvae were reduced dramatically feeding on transgenic tobacco plants. To determine the causes of the increased resistance, both PIs and PPO as defense proteins were investigated by Northern blot and activity analysis. PIs expression and activity were dramatically induced in the TobpreproHypSys-A overexpressed plants. PPO activity was also induced substantially in transgenic plants. These data suggest that the enhanced resistance to insect larvae could result from the accumulation of PIs and PPO induced by the TobpreproHypSys-A expression in transgenic plants.