Identification of the amino acids crucial for the activities of drought responsive element binding factors (DREBs) of Brassica napus

We have previously identified two homologous groups of BnDREBs in Brassica napus, the trans-active BnDREBI and the trans-inactive BnDREBII, which provided an ideal system to study the trans-activation of DREB1/CBF. Deletion analysis indicated that the two additional regions in BnDREBI contributed little to the transcriptional activity. Domain swapping analysis indicated that all the domains contributed to the activity of BnDREBI, including the ERF/AP2 DNA binding domain. Through site-directed mutagenesis, we identified nine residues that were involved in the activity of BnDREBI, among which six residues are specific to BnDREBI, and three are common to DREB1A.