FIG 4.
RsiC negatively controls both RsiB1 and RsiB2. The transcription level of the PSMc00885-lacZ fusion carried on plasmid pMP220-885, used as a reporter of RpoE2 activity, was measured in the S. meliloti strain CBT430 (ΔrsiB1 ΔrsiB2) or CBT1051 (ΔrsiB1 ΔrsiB2 ΔrsiC) containing either the empty vector pMLBAD or pMLBAD derivatives expressing either rsiB1 or rsiB2 or mutated forms thereof (D191A), as indicated below the graphs. β-Galactosidase activity was measured on aliquots of cultures grown to exponential phase before (0 h; white bars) and after incubation for 2 h in the presence of 2% arabinose (2 h ara; pale gray bars) and after a further 1 h of incubation at either 28°C (medium gray bars) or 40°C (black bars), as described in Materials and Methods. β-Galactosidase activities are means and standard errors from at least three independent experiments.