抄録
In Arabidopsis, three transcription factors DRE-binding protein 1/C-repeat binding factors (DREB1/CBFs)
function as master switches in cold stress-inducible gene expression. Because the expression of the DREB1
genes is rapidly induced in the cold stress responses, this induction seems to be the first step for the cold stressinducible
transcriptional cascade followed by the expression of numerous genes that function in the cold stress
response. We have revealed that the 65-bp fragment of the DREB1C promoter contains positive regulatory
elements for the cold-inducible expression. By using yeast one-hybrid screens, one of Calmodulin-binding
transcription activator (CAMTA) family proteins was identified as a positive regulatory factor that interacts
with this fragment. The analyses using the multiple mutants of the CAMTA genes revealed that plants recognize
cold stress as two different signaling pathways for inducing the expression of the DREB1 genes under cold
stress conditions. In one pathway, CAMTA3 and CAMTA5 activate the expression of DREB1B and DREB1C
by a rapid temperature decrease. In another one, the circadian clock components including CCA1/LHY induce
the expression of DREB1A and DREB1C only in the daytime independent to the cooling rate. These two
signaling pathways enable plants to efficiently acquire cold acclimation capacity or freezing tolerance.
