Arabidopsis thaliana gene ABRv1 encodes an E3 ligase, its expression is induced by drought stress. To investigate the function of ABRv1, ABRv1 over expressing lines were constructed. Under drought stress, the over expressing lines OE 3 and OE 7 have 90.4% and 88.2% survival rate respectively, and ABRv1 wild type shows a survival rate of 53.8%, but the survival rate of abrv1 mutant is only 7.7%. That is to say, over expressing ABRv1 enhances the ability of drought tolerance in Arabidopsis We also detected the water loss rate of abrv1 mutant, ABRv1 wild type and ABRv1 over expressing lines, which came to an consistent conclusion with mentioned above. Furthermore, we used purified GST ABRv1 and His CPK3 protein to conduct an in vitro pull down assay and an ubiquitination assay. The pull down assay shows a physical interaction between ABRv1 and CPK3, and the ubiquitination assay shows that CPK3 protein as a target is ubiquitinated by ABRv1. In conclusion, our results demonstrate that ABRv1 playing as a positive regulator is involved in the response of drought stress via interacting with and ubiquitinating its substrate CPK3.
