Protein product of the hrpN gene of Erwinia amylovora, a phytopathogenic bacterium that causes fire blight disease. Composed of 403 amino acid residues; mol wt ≈44 kDa. Member of a class of glycine-rich, acidic, heat stable proteins that elicit the hypersensitive response as part of the plant's defense mechanism vs pathogenic bacteria. Induces systemic acquired resistance to fire blight and many other plant pathogens, enhances plant growth, and promotes insect repellency. Isoln: Z.-M. Wei et al., Science 257, 85 (1992). Prepn: S. V. Beer et al., WO 9401546; eidem, US 5849868 (1994, 1998 both to Cornell Research Foundation). Elicitation of hypersensitive response: S. V. Beer et al. in Curr. Plant Sci. Biotechnol. Agric. vol. 14, E. W. Nester, D. P. S. Verma, Eds. (Kluwer, Dordrecht, 1993) pp 281-286. Induction of plant resistance: Z.-M. Wei, S. V. Beer, Acta Hortic. 411, 223 (1996); and mode of action of disease resistance: H. Dong et al., Plant J. 20, 207 (1999). Effects on tobacco leaf cell membranes: S. M. Pike et al., Physiol. Mol. Plant Pathol. 53, 39 (1998). Blue mold resistance study in apples: G. de Capdeville et al., Plant Dis. 87, 39 (2003). Review of hrp genes and harpin proteins: J. F. Kim, S. V. Beer in Fire Blight, J. Vanneste, Ed. (CABI Publishing, Wallingford, 2000) pp. 141-161; of commercial product: Biopesticide Regulatory Action Document: Harpin Protein (U.S. EPA, 2002) 32 pp.