mRNA expression of pmrH in A4528-derived strains. qRT-PCR analysis revealed the relative mRNA expression of pmrH in A4528-derived strains that harbored 6 different amino acid substitutions compared with that in the A4528 wild-type strain (A) and in the A4528 wild-type strain and strains A4528 crrB(N141I), A4528 crrB(N141I) ΔpmrAB, A4528 crrB(N141I) ΔcrrC, A4528 crrB(N141I) ΔcrrC carrying a pACYC184 plasmid, and A4528 crrB(N141I) ΔcrrC carrying a pACYC184-3062 plasmid (B). The mRNA expression of each strain was calculated by qRT-PCR independently in quadruplicate, and statistical analysis was performed using Student's t test (*, P < 0.05; **, P < 0.01; ***, P < 0.001; ns, P > 0.05). The error bars represent SD.