Abstract
Arabidopsis transcription factors DREB1s/CBFs specifically interact with a cis-acting element DRE/CRT/LTRE involved in the expression of low-temperature-, drought- and high-salinity-inducible genes. Expression of the DREB1 genes is kept at very low level and regulated by circadian control, but induced rapidly and significantly by low temperature. In this study, we analyzed transcriptional regulation of the DREB1 genes.
Using a GUS reporter gene fused to a DREB1C promoter, we identified a region that contains cis-acting elements involved in both low temperature and circadian controls. We isolated a cDNA encoding CAMTA2, which specifically binds to the region by using the yeast one-hybrid screening. In Arabidopsis, CAMTA family, which contains a CG-1 type DNA binding domain, consists of 6 members, CAMTA1 to CAMTA6. The phylogenic and gene expression analyses suggested that the CAMTA proteins function redundantly. We found that the CAMTA proteins activated the reporter gene driven by the DREB1C promoter by using transient expression experiments with Arabidopsis protoplasts. Currently we are analyzing function of CAMTA proteins in the expression of DREB1 using T-DNA insertion mutants.
