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 65-bp region that contains cis-acting elements that function under both low temperature and circadian controls. We isolated cDNA, encoding PIF7, which specifically binds to the 65-bp region by using the yeast one-hybrid screening. We found that the PIF7 could repress DREB1C expression by transient expression assays with Arabidopsis protoplasts. In the pif7 mutant, DREB1 expression was not repressed under circadian control. These results suggest that the PIF7 functions as a transcriptional repressor for the expression of DREB1C under circadian controls.
