Identification of cDNAs from Cornus sericea that Encode a Family of Dehydrin-like Proteins

Abstract

Three cDNAs, which apparently encode a family of dehydrin-like proteins, were isolated from cold-acclimating wood tissues of Cornus sericea. The nucleic acid sequences of these cDNAs are similar to each other (minimum 58% identical). Two of the cDNAs are predicted to encode proteins of 44 and 48.6 kDa. The third cDNA did not contain the complete open reading frame, but apparently encodes a much larger protein. The predicted amino acid sequences from all three cDNAs share homology with members of the dehydrin family of proteins. This family of proteins is characterized by the presence of a highly conserved lysine-rich consensus sequence (EKKGIMDKIKEKLPG) known as the K-segment, a tract of serine residues, and in most instances, an N-terminal consensus sequence (DEYGNP) designated as the Y-segment. The cDNAs isolated from C. sericea encode putative proteins with these common motifs. Each has a tract of serine residues, and either one or two lysine-rich segments. However, a unique feature of the cDNAs from C. sericea is that they encode putative proteins having 21, 24, and 27 repeated sequences similar to the Y-segment, whereas previously identified members of the dehydrin family exhibit only one to three such repeats. The significance of this difference is not known. Dehydrins have been implicated in desiccation tolerance, and typically accumulate in response to dehydrating conditions, such as occur during drought, salt-stress, low temperatures, and during the late stages of embryogenesis. In C. sericea, expression of these transcipts changed seasonally. Northern blot analysis detected high levels of transcript in October and January, and no detectable message in June.