Heterologous expression of a basic elicitin from Phytophthora cryptogea inPhytophthora infestans increases its ability to cause leaf necrosis in tobacco

The cry-b sequence, encoding a basic elicitin (cryptogein B) from Phytophth ora cryptogea, was co-transformed into Phytophthora infestans. The copy num ber of the cry-b sequence varied in co-transformants. Nevertheless, in all cases the alien elicitin gene was transcribed, translated and the protein s ecreted in vitro from such transformants. Moreover, the secreted cryptogein B from P. infestans co-transformants increased their ability to cause a hy persensitive-response-like necrosis of tobacco leaves. It was thus conclude d that the transfer of a single gene encoding a basic elicitin from one Phy tophthora species to another can dramatically alter the phenotypic interact ion of the transformed species with tobacco.