Fig. 2

Analysis of catB and oxyR transcripts in Xoo strains. a Assays for promoter activities of catB in PXO99^A and ∆oxyR in the presence (“+”) or absence (“-”) of H₂O₂. Overnight cultures of wildtype and ∆oxyR containing a pH-catBp-lacZ transcriptional reporter were inoculated 1:100 into fresh M210 liquid medium and shaken at 28 °C until cells reached at OD₆₀₀ of 1.0, and treated with 3 mM H₂O₂ for 0.5 h. The catB promoter activity was analyzed by measuring β-galactosidase levels. 1, WT (pH-lacZ); 2, WT (pH-catBp-lacZ); 3, ∆oxyR (pH-catBp-lacZ). pH-lacZ was an empty plasmid used as the control. b Assays for catB and oxyR transcripts in PXO99^A treated with H₂O₂. Wildtype cells cultured in M210 liquid medium were exposed to H₂O₂ at 3 mM for 0.5 h, H₂O₂-untreated cells were used as the control (CK), and the total RNA was extracted with TRIzol reagent. The expression levels of catB and oxyR were detected by quantitative RT-PCR and normalized to gyrB. Bars represent standard errors of the means from three independent cultivations, and different letters above the bars denote statistically significant differences (P < 0.05, Student’s t test)