FIG. 2.

Regulation of pglA by wild-type vsrC and mutant alleles of vsrC. Concentrated supernatants of 24-h-old BSM cultures of strain AW22 (wild-type background [WT]) or from double mutant strain AW22BC (vsrB vsrC) containing the indicated plasmids were serially diluted twofold in BSM and 5 μl of each dilution (2× through 1/8×) spotted on nitrocellulose. The amount of PglA was assayed using anti-PglA antiserum and alkaline phosphatase-conjugated secondary antibody. pRKVC3 contains wild-type vsrC; pVSRC1 and pVSRC2 contain the vsrB-independent alleles vsrC1 and vsrC2, respectively. PglA−, supernatant from R. solanacearum PG3 (pglA::nptl [39]). Purified PglA (50, 25, 12, 6, and 3 μg, respectively, for each of the 5 dilutions listed at the left) was used for calibration.