Fig. 6.

FlhDC, independently of FliA, regulates the T3SS master regulator HrpL at transcriptional level through EcpC-RpoN-HrpL pathway in D. dadantii 3937. But FlhDC positively regulates transcription of ycgR₃₉₃₇ through FliA.

A. Promoter activity of ecpC was measured in the wild-type D. dadantii, the flhDC and fliA mutant strains and the flhDC and fliA complemented strains respectively.

B. Promoter activity of egcpB was measured in wild-type D. dadantii, ΔflhDC and ΔfliA strains.

C. Promoter activity of ycgR₃₉₃₇ was measured in wild-type D. dadantii harbouring empty vector pCL1920, the ΔflhDC harbouring empty vector pCL1920, the ΔfliA harbouring empty vector pCL1920 and their complemented strains.

D. Relative mRNA levels of hrpL and rpoN were examined using quantitative real time RT-PCR in the wild-type D. dadantii and the ΔflhDC. Values are a representative of three independent experiments. Three replicates were used in each experiment. Error bars indicate standard errors of the means. Asterisks indicate statistically significant differences of the means (P < 0.05 by Student’s t-test).