Characterization of a gene cluster of Phytophthora cryptogea which codes for elicitins, proteins inducing a hypersensitive-like response in tobacco

Elicitins, proteinaceous elicitors secreted by Phytophthora spp., act as inducers of a hypersensitive-like response in tobacco during incompatible interactions. We have isolated and cloned sequences encoding cryptogein and related isoforms from P. cryptogea that belong to the elicitin family. The isolation of a genomic clone led to the characterization of four clustered genes. Two of these genes encode distinct elicitins, and two genes would encode, if expressed, a class of highly acidic elicitins which had not been observed so far. Northern blots indicate that elicitin genes are expressed in the fungus grown in vitro, though at different levels. Southern hybridization revealed that elicitins are encoded by a multigene family in several other species of Phytophthora. Moreover, isolates of Phytophthora parasitica var. nicotianae, pathogenic to tobacco, which do not produce elicitins, possess several elicitin-encoding genes. Involvement of elicitins in plant-pathogen interactions is discussed.