Localization of the sporulation protein SpoIIE in Bacillus subtilis is dependent upon the cell division protein FtsZ.

SpollE is an integral membrane protein that governs the establishment of cell-specific gene transcription during the process of sporulation in Bacillus subtilis. Synthesis of SpollE commences shortly after the onset of sporulation, after which the protein localizes at sites of potential cell division near both ends of the sporangium. We now show that, within the limits of resolution of immunofluorescence microscopy, this bipolar pattern of localization observed in early-sporulating cells was superimposable with the bipolar pattern of localization of the cell division protein FtsZ. The localization of SpollE was dependent upon FtsZ because little or no localization was observed along the length of filaments that were generated by depleting sporulating cells for the cell division protein. In contrast, SpollE and FtsZ were found to co-localize at regularly spaced intervals in filaments generated by the use of a temperature-sensitive mutant of the cell division gene divlC. Finally, in cells engineered to synthesize SpollE during growth, SpollE localized at the mid-cell position, coincident with the position of FtsZ, which exhibits a medial pattern of localization in cells undergoing binary fission. These results suggest that the bipolar pattern of localization of SpollE is dictated by the sporulation-induced switch in the position of FtsZ or of other, FtsZ-associated, cell division proteins. Thus, it appears that B. subtilis has co-opted the cell division machinery as a means of localizing a cell fate determinant to the polar septum during sporulation.