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. Essential for female and male gametophyte development. Protein modification; protein ubiquitination. Interacts with CUL3A. Preferentially expressed in leaves. Down-regulated by salicylic acid (SA), ethylene, hydrogen peroxide and cold. Up-regulated by NaCl. The BTB/POZ domain mediates the interaction with some component of ubiquitin ligase complexes. May be due to an intron retention.