The activity of the transcription factor sigma (F) is confined to one (the
forespore) of two cells created by asymmetric division during sporulation i
n B. subtilis. We show that sigma (F) activation is partly governed by the
position of the gene for the unstable anti-sigma (F) factor SpoIIAB. Becaus
e cytokinesis precedes chromosome segregation, most of the chromosome is tr
anslocated into the forespore after division. We hypothesize that because s
poIIAB; enters the forespore late, SpoIIAB lost to proteolysis is temporari
ly not replenished. Thus, chromosome asymmetry would be translated into the
asymmetric distribution of SpoIIAB. Supporting this idea, transposition of
spoIIAB to sites present in the forespore at the time of division impaired
sporulation when a second pathway that participates in sigma (F) activatio
n was disabled.