Seasonal fluctuation of dehydrins is related to osmotic status in Scots pine needles

Seasonal variation in dehydrins and other soluble proteins of Scots pine (P inus sylvestris L.) needles, buds and bark were analyzed monthly for 1 year from 1998 to 1999. Dehydrin-related proteins of 60 and 56 kDa were identif ied immunologically in all tissues. The concentration of the 60-kDa dehydri n was highest during the winter (October-February) in buds and bark but inc reased in early spring (March-May) in needles. Accumulation of the 60-kDa d ehydrin in the needles in springtime was related to the decreasing, osmotic potentials of the needles. The 56-kDa dehydrin was present only during the growing season, as was a 50-kDa dehydrin, which only appeared in bud and b ark tissues. The soluble protein concentration of needles did not differ si gnificantly between seasons, but in bark and bud tissues the protein concen trations were at their lowest level in newly grown tissues (June-August). T he level of several polypeptides was higher during the winter-spring period than in the growing season, especially in bark and bud tissues. These prot eins may be related to cold hardiness or dormancy in overwintering Scots pi ne. Dehydrin-related proteins in needles are linked to springtime changes i n the osmotic status of needles rather than to their cold acclimation.