Polymorphism of thermostable proteins in soft wheat seedlings during low-temperature acclimation

The accumulation of thermostable stress proteins during hardening was studi ed in etiolated seedlings of spring (cvs. Rollo, Drott, Angara-86, and Tyum enskaya-80) and winter (moderately frost-resistant cv. Bezostaya-1 and high ly frost-resistant cvs. Irkutskaya ozimaya and Zalarinka) wheat using one-d imensional SDS-PAGE. Hardening was performed at 4 degreesC for nine days. S eedling tolerance to low subzero temperatures was estimated from electrolyt e leakage and seedling survival after freezing. Hardening of all wheat geno types tested resulted in the accumulation of thermostable cold-regulated (C OR) polypeptides with mol wts of 209, 196, 169, 66, 50, and 41 W. A densito metric analysis demonstrated a close correlation between the cultivar frost tolerance and the relative content of COR proteins, which evidently indica ted the protective functions of the latter, These results led us to suggest that the level of specific protective agents, thermostable high-molecular- weight COR polypeptides in particular, determines the degree of plant frost resistance within a particular plant species.