Characterization of an endo-1,3-beta-D-glucanase produced during the interaction between the mycoparasite Stachybotrys elegans and its host Rhizoctonia solani

The mycoparasite Stachybotrys elegans produces, in addition to a previously purified 94-kDa 1,3-beta- glucanase, at least three extracellular 1,3-beta -glucanases (75, 110, and 180 kDa) when grown on purified cell wall of Rhiz octonia solani. We purified to homogeneity an endo-1,3-beta-glucanase of 75 kDa which possesses a low K-m value of 20 mu g laminarim.mL(-1) and is mos t active at pH 5.0 and 40 degrees C Polyclonal antibodies raised against bo th the 75- and 94-kDa 1,3-beta-glucanases indicate that they are immunologi cally related but do not cross-react with the 110- and 180-kDa glucanases. Exposure of growing hyphal tips of R. solani to the pure 75-kDa 1,3-beta-gl ucanase caused them to swell and lyse. A transient increase of the 75-kDa 1 ,3-beta-glucanase with a concomitant decrease of the 94-kDa 1,3-beta-glucan ase and the appearance of a 20-kDa protein were observed at the point of in teraction between R. solani and Stachybotrys elegans on plates. Evidence su ggesting a precursor-product relationship between the two 1,3-beta-glucanas es is provided. Our results indicate that the 75-kDa 1,3-beta-glucanase may be involved in Stachybotrys elegans mycoparasitism.