DEHYDRINS

   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 Y_nSK₂, K_n, K_nS, SK_n, and Y₂K_n types.