ISOLATION AND EXPRESSION OF COLD SPECIFIC GENES IN POTATO (SOLANUM-SOGARANDINUM)

The expression of genes corresponding to twenty four cDNA clones (Ssci ) representing cold induced mRNAs was examined by Northern blot hybrid ization in potato plantlets treated with cold; NaCl, sorbitol, water a nd ABA and is illustrated by data representative of the four expressio n patterns. The response of the genes to cold was examined in two gene tically related potato species: a cold tolerant acclimating Solanum so garandimum and a cold sensitive cultivated Solanum tuberosum, cv. Cisa . The results of Northern blots revealed that only genes corresponding to four of the analyzed clones (Ssci1, Ssci12, Ssci17 and Ssci20) sho wed much higher levels of accumulation of the corresponding transcript s during cold treatment in the cold resistant potato as compared with the cold sensitive one. On the other hand, a few other clones (Ssci3, Ssci4, Ssci6, Ssci13, Ssci21 and Ssci29) showed higher levels of the t ranscripts accumulation in the cold sensitive potato. The remaining 14 clones showed similar levels of the accumulation of the corresponding transcripts under cold in both potato types. With the exception of Ss ci12, the clones were not induced by ABA: NaCl, sorbitol or water trea tments. There were no differences in the levels of the corresponding t ranscripts between the control plantlets and those treated with ABA, N aCl, sorbitol and water, The expression of the clones was not regulate d in the day/night cycle; however, the Ssci1 and Ssci2 clones, encodin g two different S-adenosyl-L-methionine decarboxylases (SAMDC), were u p-regulated at night. The level of induction of the Ssci12 clone, enco ding the TAS14 protein (dehydrin), was much higher following treatment s with ABA, NaCl and sorbitol than with cold and the gene does not res pond to water stress. Higher activity of the genes corresponding to th e Ssci1, Ssci12, Ssci17 and Ssci20 clones during cold hardening in the cold resistant potato suggests that their expression is associated wi th the development of freezing resistance. Among them, the genes corre sponding to the Ssci17 and Ssci20 clones are cold acclimating specific ones (cas). (C) 1998 Elsevier Science Ireland Ltd, All rights reserve d.