HrpNEP, from the gram-negative pathogen, Erwinia pyrifoliae, is a member of the harpin group of proteins, inducing pathogen resistance and hypersensitive cell death in plants. When the hrpNEP gene driven by the OsCc1 promoter was introduced into tobacco plants via Agrobacterium-mediated transformation, their resistance to the necrotrophic fungal pathogen, Botrytis cinerea, increased. Resistance to B. cinerea was correlated with enhanced induction of SA-dependent genes such as PR-1a, PR2, PR3 and Chia5, of JA-dependent genes such as PR-1b, and of genes related to ethylene production, such as NT-EFE26, NT-1A1C, DS321, NT-ACS1 and NT-ACS2. However the expression of NPR1, which is thought to be essential for multiple-resistance, did not increase. Since the pattern of expression of defense-related genes in hrpNEP-expressing tobacco differed from that in plants expressing hpaGXoo from Xanthomonas oryzae pv. Oryzae, these results suggest that different harpins can affect the expression of different defense-related genes, as well as resistance to different plant pathogens.

Keywords: Erwinia pyrifoliae, hrpNEP, NPR1, SA