Figure 5. σ^H activity is only required in predivisional cells.

A. Diagram representing the strategy used to induce the degradation of target proteins in predivisional cells about to undergo polar septation. Before polar septation, Spo0A becomes phosphorylated and controls the expression of several genes required for entry into sporulation. Expression of sspB^Ec from promoters activated by Spo0A would trigger degradation in predivisional cells, before polar septation occurs. We specifically used the promoter of spoIIE to drive sspB^Ec expression.

B. Degradation of YtsJ-GFP-ssrA* in predivisional cells. Membranes were stained with FM 4–64. Scale bar, 1 μm.

C. Micrographs of wild type sporangia (WT), σ^H mutant sporangia (ΔsigH) and sporangia in which σ^H is tagged with ssrA* (σ^H-ssrA*) in the absence of SspB^Ec (No deg.) or when SspB^Ec is produced in predivisional cells from P_spoIIE (Deg. prediv.), in the forespore from P_sspE(2G) (Deg. FS) or in the mother cell from P_cotE (Deg. MC). Pictures were taken 3 (t3) and 6 (t6) hours after sporulation induction. Membranes stained with FM 4–64 (red) and Mitotracker green (green) are shown for t3 and t6. Phase contrast pictures are only shown for t6. Scale bar, 1 μm.