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   Dehydrin proteins and their transcripts have been shown to accumulate during seasonal cold acclimation in buds, bark, xylem, shoot apices, and seedlings of a number of woody plant species. Because dehydrins have hydrophilic properties and amphipathic peptide domains within their structure, they are believed to interact with endomembranes and protect them and other cellular proteins from the destabilizing effects of sub-zero temperatures and/or freeze-induced desiccation. Although the in vivo role of dehydrins has not been demonstrated definitively as yet, several in vitro and immunolocalization studies have demonstrated their role in cryoprotection of proteins, propensity for hydrophobic interactions, ability to bind lipid vesicles, and localization close to the plasma membrane. All of these findings support their potential in vivo role in stabilizing cells under cold stress.

    Dehydrins are characterized by a highly conserved 15-mer lysine rich sequence, called the K segment, which may be present in one or several copies. The K segment can form an amphiphatic a-helix structure that may have a chaperone-like function in stabilizing partially denatured proteins or membranes. Apart from the K segment that is present in all dehydrins, dehydrins may also posses one or more Y (DEYGNP) and/or S segments (serine cluster) in their sequence. Dehydrins can thus be categorized into classes based on number and position of these conserved motifs, for example YnSK2, Kn, KnS, SKn, and Y2Kn types.

    Using a molecular genetic approach, the Rowland lab has identified and isolated genes that respond to cold treatment in blueberry and thus are good candidates for involvement in cold hardiness development. We have shown that 65, 60, and 14 kDa dehydrins accumulate during seasonal development of cold hardiness of blueberry to become the most highly abundant proteins in floral buds. We have found a good correlation between levels of dehydrins and cold hardiness levels in all the blueberry genotypes examined. We have further demonstrated that dehydrin upregulation and downregulation in blueberry buds is specifically associated with changes in bud cold hardiness rather than with dormancy transitions that coincide with acclimation/ deacclimation cycles. A full-length 2.0 kb cDNA clone encoding the 60 kDa dehydrin (GenBank accession # AF030180) and a full-length 0.5 kb cDNA clone encoding the 14 kDa dehydrin (# AY660959) have been isolated from a cDNA library constructed from cold acclimated floral bud RNA. Both of these are Kn type dehydrins.