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 AvrBs3Δrep16. 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 AvrBs3Δrep16, respectively. We found that recognition specificity resides in the Bs3 and Bs3-E promoters and is determined by binding of AvrBs3 or AvrBs3Δrep16 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.