Dh. Yang et al., Synthesis of the sigma(D) protein is not sufficient to trigger expression of motility functions in Bacillus subtilis, J BACT, 181(9), 1999, pp. 2942-2946
The gene encoding sigma(D), sigD, is transcribed from two promoter regions,
the fla/che promoter region in front of the fla/che operon and P-sigD dire
ctly in front of sigD. If sigma(D) is translated from transcripts originati
ng from P-sigD, the cell is unable to express motility functions but synthe
sizes autolysins. Therefore, one function of the additional promoter is to
allow the cell to express autolysins without expressing motility functions
as well.