Seasonal Changes of Dehydrins in Betula Pendula Roth Xylem and Bark During Formation of Resistance to Cold in Permafrost Zone

Abstract

In the one-year shoots of silver birch (Betula pendula Roth) of Central Yakutia population in preparation for dormancy (August, September) we observed the accumulation of a number of total proteins what is probably associated with the plant wintering over under the permafrost zone conditions. Their level remains high for a long winter. The content of these polypeptides is sharply reduced during the resumption of growth in the spring. Polymorphism of total proteins at some birches in two variable domains 23-27 and 16-18 kDa is detected. Two major groups of low molecular weight (17, 18 and 21 kDa) and medium weight (66 and 69 kDa) dehydrins are firstly found in the composition of seasonally changing dehydrin specific tissue – xylem and birch bark. Dehydrin of low molecular weight had a more pronounced seasonal dynamics than dehydrins of middle one. Their content was the highest during the dormancy when the plant reaches a maximum freezing tolerance. Dehydrin 17, 18 and 21 kDa disappeared during the growing season. The dehydrins level in the xylem at dormancy was higher than in the cortex, which is probably due to the different tissue strategies for cryotolerance. Dehydrin and total proteins of Central Yakutia population of B. pendula showed features of adaptive changes that indicate their important role in resistance to the extreme conditions of the permafrost zone.