EFFECT OF FUSICOCCIN ON THE ACTIVITY AND CARBOHYDRATE SPECIFICITY OF LECTINS FROM CROWN CELL-WALLS AND THE FROST-RESISTANCE OF WINTER-WHEATPLANTS

Hemagglutinating activity and carbohydrate specificity were determined in lectin-containing fractions from the walls of crown cells of winte r wheat (Triticum aestivum L.) plants. The effect of fusicoccin (FC) w as investigated using fractions obtained from plants hardened for 7 da ys at 2 degrees C and from untreated plants. The FC concentration (5 x 10(-7) M) used in this study increased the frost resistance of the pl ants. In unhardened plants, lectin activity was four times higher in t he plants treated with FC than in the untreated plants. Hardening caus ed a three-fold increase in activity, and, when it was coupled with FC treatment, this effect was doubled. In unhardened plants, the affinit y of the fraction containing lectins for UDP-Glu and Glu-6-phosphate w as higher than for Glu, Gal, Sue, galactosamine, and N-acetyl-glucosam ine. In unhardened plants treated with FC, the affinity of lectins for UDP-Glu was lower, yet it remained at the level of the control in the case of other carbohydrates, except Gal, which did not interact with the lectins. Hardening increased the lectin affinity for Gal, decrease d the affinity for UDP-Glu, and had no effect on the lectin affinity t oward other carbohydrates. The lectin affinity for Glu and aminosugars increased in the plants hardened and treated with FC. Both frost resi stance of the plants and the activity of lectins increased after cold hardening and treatment with FC. The changes in the affinity of the le ctins for various carbohydrates were similar when caused by each of th ese two treatments but differed when the treatments were combined. Inc rease in the lectin activity may be caused by the effect of low harden ing temperature stimulating the synthesis of proteins, lectins among o thers. Treatment with FC is supposed to intensify protein synthesis an d cause further increase in lectin activity leading to changes in the frost resistance of cells by controlling protein-carbohydrate interact ions between the cell wall and plasma membrane during freezing.