Clp upregulates transcription of engA gene encoding a virulence factor in Xanthomonas campestris by direct binding to the upstream tandem Clp sites

摘要: In Xanthomonas campestris, the causative agent of black rot in crucifers, endoglucanase level is greatly decreased mutant deficient Clp, a homologue cyclic AMP receptor protein (CRP). It established that Clp has same DNA binding specificity as CRP at positions 5, 6, and 7 (GTG motif) half site. this study, engA transcription initiation site was determined by 5′ RACE method, two consensus Clp-binding sites, I II centered −69.5 −42.5, respectively, were located. Transcriptional fusion assays indicated activates transcription. Site-directed mutagenesis position 5 GTG motif essential for both DNA-protein complex formation electrophoretic mobility shift vivo. addition, mutation drastically reduces promoter activity, indicating to exerts synergistic effect on activation II. appears be first X. campestris gene known activated via direct promoter.