Abstract
ICE1 induces expression of DREB1A/CBF3 to regulate cold signaling and cold tolerance. However, it is unknown how ICE1 is activated by cold signaling. Recently, we have found that sumoylation of ICE1 at K393 regulates cold signaling. In this study, we have evaluated roles of serine/threonine residues around the K393 to find the residues for activation of ICE1. We replaced 6 serine/threonine residues around the K393 to alanine and the substitution of a certain serine enhanced transactivation activity of ICE1. Overexpression of the ICE1 (S to A) conferred more freezing tolerance than that of ICE1 (WT) in Arabidopsis. These results suggest that the serine residue has roles in the activation of ICE1.
