Plant pathogen recognition mediated by promoter activation of the pepper Bs3 resistance gene

Plant disease resistance (R) proteins recognize matching pathogen avirulence proteins. Alleles of the pepper R gene Bs3 mediate recognition of the Xanthomonas campestris pv. vesicatoria (Xcv) type III effector protein AvrBs3 and its deletion derivative AvrBs3 Delta rep16. Pepper Bs3 and its allelic variant Bs3-E encode flavin monooxygenases with a previously unknown structure and are transcriptionally activated by the Xcv effector proteins AvrBs3 and AvrBs3 Delta rep16, respectively. We found that recognition specificity resides in the Bs3 and Bs3-E promoters and is determined by binding of AvrBs3 or AvrBs3 Delta rep16 to a defined promoter region. Our data suggest a recognition mechanism in which the Avr protein binds and activates the promoter of the cognate R gene.