Low temperature-induced expression dehydrins in deciduous fruit crops and their relation to cold acclimation and/or dormancy

Two separate experiments were conducted to identify and characterize protein changes specifically associated with either cold acclimation or dormancy in temperate fruit crops. This was accomplished by using, in the first experiment, sibling deciduous and evergreen peach genotypes to study seasonal patterns of cold hardiness and protein changes in-bark tissues. The deciduous peach genotype enters endodormancy during fall whereas the evergreen peach does not. In the second study, differential expression of previously identified 65- and 60-kD dehydrin proteins and their association with cold acclimation or endodormancy in blueberry buds were evaluated. To achieve this, cold hardiness or dormancy status of blueberry buds was differentially modified by manipulating the temperature. Protein profiles and their immunoblots, before and after these treatments, were then compared with changes in cold hardiness and dormancy. Following are the results from these studies: 1) a 60-kD peach-bark protein is closely associated with seasonal transitions and extent of cold hardiness, rather than endodormancy, in sibling peach genotypes; 2) immunoblot data indicated that the 60-kD protein was a dehydrin protein; 3) the blueberry cultivar 'Tifblue' exhibited cold acclimation during a 4 degrees C treatment (for 3 weeks) which also satisfied one-half of its chilling requirement; this was paralleled by an accumulation of 65- and 60-kD dehydrin-like proteins; 4) levels of these proteins declined following a 2-week exposure of buds to 15/12 degrees C (D/N) (a treatment that resulted in deacclimation but did not negate chill unit accumulation). These results suggest that a 60-kD dehydrin protein in peach and 65- and 60-kD dehydrin proteins in blueberry buds may be specifically associated with cold acclimation, but not with dormancy.