A novel elicitin necrotic site revealed by alpha-cinnamomin sequence and site-directed mutagenesis

Elicitins are 10 kDa proteins secreted by Phytophthora fungi, that elicit r esistance against certain plant pathogens. Various natural molecules, mutat ed recombinant elicitins and synthetic peptides were previously shown to di fferentially induce in tobacco leaf necrosis and defence genes, activities borne by several sites which were identified. We report a novel necrosis-de termining residue at position 25, revealed by the comparison of the necroti c activity and sequence of alpha-cinnamomin with those of other known elici tins. Using a modified recombinant beta-cryptogein, expressed in Pichia pas toris, we show that the substitution of asparagine 25 by a serine leads to a significant enhancement of the necrotic activity. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.