May act as a substrate-specific adapter of an E3 ubiquitin-protein ligase complex (CUL3-RBX1-BTB) which mediates the ubiquitination and subsequent proteasomal degradation of target proteins (By similarity). Involved in the regulation of basal defense responses against pathogens, and may be implicated in the cross-talk between the SA- and JA-dependent signaling pathways. Protein modification; protein ubiquitination. Interacts with TGA2, TGA3, TGA5, TGA6 and TGA7. Up-regulated following pathogen challenge or salicylic acid (SA) treatment, and down-regulated by methyl jasmonic acid (MeJA) treatment. The BTB/POZ domain mediates the interaction with some component of ubiquitin ligase complexes. Enhanced susceptibility to the virulent bacterial pathogen Pseudomonas syringe and to the fungal pathogen Erysiphe cichoracearum (powdery mildew).