DIFFERENTIAL EFFECT OF PURIFIED SPRUCE CHITINASES AND BETA-1,3-GLUCANASES ON THE ACTIVITY OF ELICITORS FROM ECTOMYCORRHIZAL FUNGI

Two chitinases (EC 3.2.1.14) and two beta-1,3-glucanases (EC 3.2.1.39) were purified from the culture medium of spruce (Picea abies [L.] Kar st.) cells to study their role in modifying elicitors, cell walls, gro wth, and hyphal morphology of ectomycorrhizal fungi. The 36-kD class I chitinase (isoelectric point [pI] 8.0) and the 28-kD chitinase (pi 8. 7) decreased the activity of elicitor preparations from Hebeloma crust uliniforme (Bull. ex Fries.) Quel., Amanita muscaria (L.) Pers., and S uillus variegatus (Sw.: Fr.) O.K., as demonstrated by using the elicit or-induced extracellular alkalinization in spruce cells as a test syst em. In addition, chitinases released monomeric products from the walls of these ectomycorrhizal fungi. The beta-1,3-glucanases (35 kD, pi 3. 7 and 3.9), in contrast, had little influence on the activity of the f ungal elicitors and released only from walls of A. muscaria some polym eric products. Furthermore, chitinases alone and in combination with b eta-1,3-glucanases had no effect on the growth and morphology of the h yphae. Thus, it is suggested that apoplastic chitinases in the root co rtex destroy elicitors from the ectomycorrhizal fungi without damaging the fungus. By this mechanism the host plant could attenuate the elic itor signal and adjust its own defense reactions to a level allowing s ymbiotic interaction.