THE EXPRESSION OF EXTRACELLULAR PROTEASE ASSOCIATED WITH ZOOPHTHORA RADICANS VIRULENCE INDUCED BY PLUTELLA XYLOSTELLA
根虫瘟霉转寄主过程中毒力相关胞外蛋白酶系的诱导表达

Zoophthora radicans is a specific insect-pathogenic fungus with a broad host range. The relationship between virulence and extracellular proteases has been studied. It was indicated that there was no correlation between extracellular protease activities of various Z. radicans isolates and their virulence against Plutella xylostella, while Z. radicans reisolates from P. xylostella resulted in a gradual increase inextracellular protease production as well as virulence against P. xylostella,and there were correlated to each other in a certain extent. Electrophoresis detection showed that ARSEF1342, the original strain (R0produced three protease bands corresponding to molecular masses of 148kD, 153kD and 162kD respectively,whereas the band of 148kD was abruptly lost in the Z. radicans reisolates (R1~R4) , but the 153kD band gradually became obvious along with passages of reisolates. Comparably reliable correlation betweenvirulence against P. xylostella and the relative concentration of 153kD or 148kD band was found byregression analysis. This indicated that induced expression of high substrate-specific extracellular protease was enhanced during passages of reisolate from P. xylostella, which will consequently facilitate reisolates foR NON-ORIGINAL HOST INFECTION AND DISEASE FORMATION.