TRANSCRIPTS ACCUMULATING DURING COLD-STORAGE OF POTATO (SOLANUM-TUBEROSUM L) TUBERS ARE SEQUENCE RELATED TO STRESS-RESPONSIVE GENES

During the adaptation of plants to low temperature, changes in gene ex pression can be induced in a variety of tissues. Low-temperature-regul ated gene expression was studied in cold-stored potato (Solanum tubero sum L.) tubers by two-dimensional electrophoresis of in vitro translat ion products. As a response to cold treatment, the relative amount of mRNA encoding at least 26 polypeptides changed. By differential screen ing of a cDNA library, 16 clones corresponding to cold-inducible trans cripts were isolated. They were classified into four non-cross-hybridi zing groups. RNA hybridizations using representative clones from each group revealed different temporal accumulation patterns for the cold-i nducible transcripts. mRNAs homologous to the cDNA clones were first d etectable after 1 to 3 d of cold treatment, and the highest lever of e xpression was reached after 3 to 7 d. Transcripts corresponding to cDN A clones Cl13 and Cl19 were transiently expressed, whereas the steady- state level remained high for cDNA clones Cl7 and Cl21 during the cold storage period of 4 weeks. The DNA sequences of two cDNA crones, Cl7 and Cl19, have been determined. The polypeptide predicted from the DNA sequence of Cl19 is sequence related to small heat-shock proteins fro m other plant species. The deduced protein sequence of Cl7 exhibits st rong homology to the dehydrin/RAB group of dehydration stress- and abs cisic acid-inducible polypeptides and to cold-induced proteins from Ar abidopsis and spinach.