MODULATION OF PROTECTIVE REACTIONS IN COTTON DURING STRESSES IN RESPONSE TO THE ACTION OF PROBABLE ELICITORS OF BETA-1,3-1,6-GLUCAN NATURE

The effects of beta-1,3;1,6-glucans on cotton seedlings subjected to t hermal stress or infected with wilt were studied. The protective effec ts were measured by increases in the levels of beta-1,3-glucanase and protein kinase C(PKC). beta-1,3;1,6-Glucans produced by enzymatic tran sformation of laminarin using mollusk endo-beta-1,3-glucanase displaye d elicitor properties; the compounds had low and medium molecular weig ht and are termed Lm and Mm, respectively. The same properties were fo und in a medium-molecular-weight glucan (Mp) produced in a similar pro cess mediated by potato endo-beta-1,3-glucanase. Lm produced a twofold increase in beta-1,3-glucanase activity in three-day-old cotton seedl ings subjected to heat stress (48 degrees C) or infected with wilt. Mp and Mm stimulated beta-1,3-glucanase and PKC in 12-day-old seedlings subjected to thermal stresses (48 or 4 degrees C); the effects were mo re pronounced in roots than in leaves. The effects of Mp and effectors of PKC (1,2-dioleoylglycerol (DG), phosphatidylserine (PS), and 12-O- tetradecanoylphorbol 13-acetate (TPA) and the inhibitor Permixin B(J)) on PKC and beta-1,3-glucanase activities in cotton callus cell cultur es was studied. The combination of Mp with PS increased the activity o f PKC nearly twofold. Mp combined with PS and DG produced no additiona l activation of PKC, and the effect of Mp in the presence of TPA, a su bstance that reportedly influences PKC by a DG-like mechanism, was opp osite: the addition of Mp decreased the enzyme activity to the initial level. Changes in beta-1,3-glucanase activity followed the changes in PKC in nearly all cases. Mp in the presence of J or J combined with P KC activators always suppressed the inhibitory effects, and both enzym es were activated on certain occasions. This stimulatory effect was es pecially strong with the mixture of Mp + PS + DG + J.