Figure 7

Developmental control by Euo. (a) LacZ-based promoter-probe plasmids were co-transformed into E. coli with a plasmid carrying euo under the control of an IPTG-inducible promoter (pSRK-Gm) (Khan et al., 2008). As a control, we used an empty expression vector. The LacZ activity was determined and the data represent mean values±standard deviation of three biological triplicates. When Euo expression is induced, the LacZ activity strongly decreased for the P_queF, P_rpoB, P_rhs9 and P_{wcw_1705} and slightly decreased for the P_{wcw_0066}, P_hrcA and P_gltT. (b) Transcriptional interference assays as in (a) with plasmids expressing the point mutant versions of Euo as indicated in the panel. Mutations are located in the two TorI-like wHTH arranged in tandem (individually and in combination) and cloned in a pBAD22 vector under the control of an arabinose-inducible promoter. These plasmids were co-transformed into E. coli with the plasmid carrying the P_queF-lacZ fusion. Euo strongly decreased (by 60%) the LacZ activity for the P_queFpromoter, while the triple mutant only decreased the activity by 30%. (c–e) Temporal expression of Euo target genes was assessed by qRT-PCR at different time p.i. The transcript abundance (%) during the developmental cycle was determined for each Euo target gene. Data are mean values±standard deviation of three independent experiments. Most of the genes exhibited a peak of expression during the mid-phase of the developmental cycle and were considered as mid-phase genes. Wcw_1215 is an early gene since the peak of transcript abundance was at 3 h p.i. whereas katA is a late gene since the expression remained stable during the late phase.