Figure 1.

SA-Mediated Redox Control of TGA1.

Després et al. show that TGA1 is present in an oxidized state in Arabidopsis leaves in the absence of SA, as manifested by the formation of a disulfide bridge between two conserved Cys residues. SA accumulation causes the reduction of these Cys residues, and the reduced form of TGA1 is capable of interacting with the regulatory protein NPR1. The interaction with NPR1 enhances the DNA binding of reduced TGA1, which, like other members of the TGA family, binds specifically to SA-regulatory sequences found in the promoters of numerous PR genes in an NPR1-dependent manner. TGA4 contains conserved Cys residues similar to TGA1 and also is likely to be redox regulated in this manner.