LOCALIZATION OF THE SPORULATION PROTEIN SPOIIE IN BACILLUS-SUBTILIS IS DEPENDENT UPON THE CELL-DIVISION PROTEIN FTSZ

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