DEHYDRINS - A COMMONALITY IN THE RESPONSE OF PLANTS TO DEHYDRATION AND LOW-TEMPERATURE

Among proteins that accumulate in plants in response to dehydrative fo rces or low temperature, dehydrins (late embryogenesis abundant [Lea] D11 family) have been the most commonly observed. Dehydrins are compos ed of several typical domains joined together in a few characteristic patterns, with numerous minor permutations. These domains include one or more putative amphipathic alpha-helix forming consensus regions, a phosphorylatable tract of Ser residues, and an N-terminal consensus se quence. Lesser conserved domains are also present at various positions , particularly between the putative alpha-helix forming domains, where they may occur as tandem repeats. This medley of permutations is mirr ored by a wide size range of dehydrin polypeptides from less than 100 to nearly 600 amino acid residues. As of yet, the fundamental biochemi cal mode of action of dehydrins has not been demonstrated, but a numbe r of immunolocalization and cell fractionation studies have establishe d that dehydrins can be located in the nucleus or cytoplasm. Furthermo re, it appears that these proteins associate with macromolecules rangi ng from nucleoprotein complexes in the nucleus to an endomembrane shea th in the cytoplasm. At present, all observations are consistent with a hypothesis that dehydrins are surfactants capable of inhibiting the coagulation of a range of macromolecules, thereby preserving structura l integrity.