Expression of SK3-type dehydrin in transporting organs is associated with cold acclimation in Solanum species

The expression of a gene, encoding a dehydrin protein designated as DHN24 was analyzed at the protein level in two groups of Solanum species differing in cold acclimation ability. The DHN24 protein displays consensus amino acid sequences of dehydrins, termed K- and S-segments. The S-segment precedes three K-segments, classifying the protein into SK₃-type dehydrins. A group of Solanum species able to cold acclimation constituted by S. sogarandinum and S. tuberosum, cv. Aster, and a second one composed of a S. sogarandinum line, that lost ability to cold acclimation, and of S. tuberosum, cv. Irga, displaying low ability to cold acclimation were studied. Under control conditions, noticeable levels of the DHN24 protein was observed in stems, tubers, and roots of Solanum species. No protein was detected in leaves. During low temperature treatment the DHN24 protein level substantially increased in tubers, in transporting organs and in apical parts, and only a small increase was observed in leaves. The increase in protein abundance was only observed in the plants able to cold acclimate and was found to parallel the acclimation capacity. Upon drought stress, the DHN24 level decreased in stems and in leaves, but increased in apical parts. These results suggest that Dhn24 expression is regulated by organ specific factors in the absence of stress and by factors related to cold acclimation processes during low temperature treatment in collaboration with organ-specific factors. A putative function of the SK₃-type dehydrin proteins during plant growth and in the tolerance to low temperature is discussed.