CHARACTERIZATION OF A GENE-CLUSTER OF PHYTOPHTHORA-CRYPTOGEA WHICH CODES FOR ELICITINS, PROTEINS INDUCING A HYPERSENSITIVE-LIKE RESPONSE INTOBACCO

Elicitins, proteinaceous elicitors secreted by Phytophthora spp., act as inducers of a hypersensitive-like response in tobacco during incomp atible interactions. We have isolated and cloned sequences encoding cr yptogein and related isoforms from P. cryptogea that belong to the eli citin family. The isolation of a genomic clone led to the characteriza tion of four clustered genes. Two of these genes encode distinct elici tins, and two genes would encode, if expressed, a class of highly acid ic elicitins which had not been observed so far. Northern blots indica te that elicitin genes are expressed in the fungus grown in vitro, tho ugh at different levels. Southern hybridization revealed that elicitin s are encoded by a multigene family in several other species of Phytop hthora. Moreover, isolates of Phytophthora parasitica var. nicotianae, pathogenic to tobacco, which do not produce elicitins, possess severa l elicitin-encoding genes. Involvement of elicitins in plant-pathogen interactions is discussed.