Fig 6. The identified transcriptional and translational regulation of sigG diminishes sigG expression by 4-6-fold and is required to prevent aberrant activity of σ^G.

(A, B) Expression of a P_sigG reporter is increased by 4-6-fold in the absence of the four regulatory features identified in this study. β-Galactosidase production was monitored during sporulation of strains harboring P_sigG-sigG^1-28-lacZ (^WTP_sigG-lacZ; open circles) or a variant in which all four features of sigG that dampen expression were simultaneously removed or repaired, ^15ntP_sigG^mut7-ATG-^RSSsigG^2-28-lacZ (^quadP_sigG-lacZ; closed circles) (strains EBM177 and EBM262, respectively.) Note that (B) provides a zoomed view of the data from the boxed area of (A). (C, D) Expression of sigG from regulatory sequences lacking the four regulatory features identified in this study causes aberrant σ^G activity during a time course of sporulation. β-Galactosidase production from (C) the σ^F-dependent P_spoIIQ-lacZ reporter or (D) the σ^G-dependent P_sspB-lacZ reporter was monitored during sporulation of strains in which sigG was expressed from its wild type regulatory sequences (^WTP_sigG-sigG; open squares) or from regulatory sequences modified to remove or repair the four features identified in this study to dampen sigG expression (^quadP_sigG-sigG; closed squares). (P_spoIIQ-lacZ strains were CFB429 and CFB431, respectively. P_sspB-lacZ strains were CFB435 and CFB437, respectively.) The black arrow in (D) indicates aberrant σ^G activity at early times of sporulation. The timing of the σ^F-to-σ^G switch, between sporulation hours 2.5 and 3, is indicated in each panel by a dashed gray line. For all panels, error bars indicate ± standard deviations based on three independent experiments.