PROMOTERS FROM KIN1 AND COR6.6, 2 HOMOLOGOUS ARABIDOPSIS-THALIANA GENES - TRANSCRIPTIONAL REGULATION AND GENE-EXPRESSION INDUCED BY LOW-TEMPERATURE, ABA, OSMOTICUM AND DEHYDRATION

The Arabidopsis thaliana genes kin1 and cor6.6 belong to the same fami ly and were expressed at higher levels following low temperature and A BA treatments. nan attempt to elucidate the mechanism of gene regulati on by low temperature, the relationship between low-temperature- and a bscisic acid (ABA)-induced gene expression and possible differential e xpression of the two genes, we have cloned a 5.3 kb genomic fragment h arboring kin1 and cor6.6 and their respective 5' sequences. The putati ve promoters of both genes were fused to the beta-glucuronidase (GUS) coding sequence and GUS expression was analysed in transgenic tobacco and A arabidopsis plants. The cor6.6 promoter produced a higher bas al level of expression than the kin1 promoter in transgenic tobacco. Enz yme assays of inducible GUS activity in transgenic Arabidopsis and tob acco plants showed that GUS activity directed by both kin1 and cor6.6 promoters was significantly induced by ABA, dehydration and osmoticum, but not by low temperature. Northern analysis revealed, in contrast, that GUS mRNA was significantly induced in these transgenic plants by low temperature. Further analysis showed that, at low temperature, GUS protein synthesis from the induced GUS mRNA was inhibited. Together t hese results reveal induction of kin1 and cor6.6 transcription by low temperature, exogenous ABA and dehydration. However, low-temperature e xpression is dramatically reduced at the translational level.