The dynamics of Rx1 interactions and activation of extreme resistance. Rx1 and NbGlk1 binding to DNA segments with and without the GLK cis-acting motif are shown. A, the autoinhibited state (4). RanGAP2 (green) retains Rx1 in the cytoplasm and increases Rx1 protein stability (8). Upon entry into the nucleus, NbGlk (orange triangle) binds the Rx1 CC domain (blue oval). Townsend et al. (10) show that NbGlk1 recruits Rx1 binding to nuclear DNA, and Rx1 prevents NbGLK1 from binding GLK cis-acting elements (red rectangle). B, the activated state. Upon PVX infection, the PVX CP106 binds the LLR domain (striped arc), initiating a conformational change to Rx1's activated form. Within the nucleus, NbGlk1 recruits Rx1 to nuclear DNA. In the Rx1-activated state, NbGlk1 is able to bind to GLK binding sites and activate transcription of genes inducing extreme resistance. As Rx1 overexpression in the presence of CP105 can induce hypersensitive response and NbGlk does not, additional Rx1-interactors are proposed (yellow shapes). PM, plasma membrane; NB, nucleotide binding site.