Two BTB proteins function redundantly as negative regulators of defense against pathogens in Arabidopsis

The BTB domain is a protein–protein interaction motif found throughout eukaryotes. Here we report the identification of two closely related BTB domain-containing proteins, POZ/BTB CONTAINING-PROTEIN 1 (POB1) and POB2, as negative regulators of defense against pathogens. In yeast two-hybrid assays, POB1 and POB2 dimerize through their BTB domains. The pob1–1 pob2–1 double mutant plants exhibited enhanced resistance against the fungal pathogen Botrytis cinerea and the oomycete pathogen Hyaloperonospora arabidopsidis Noco2. Double knockout, but not single mutants of pob1–1 and pob2–1, displayed enhanced sensitivity to growth inhibition by jasmonic acid (JA). In addition, expression of the JA-responsive defensin gene PDF1.2 is enhanced in the pob1–1 pob2–1 double mutant. Our data suggest that POB1 and POB2 function redundantly as negative regulators of JA-mediated pathogen resistance responses.