Dual promoters are responsible for transcription initiation of the fla/che operon in Bacillus subtilis.
The fla/che region contains more than 30 genes required for flagellar synthesis and chemotaxis in Bacillus subtilis, including the gene for the flagellum-specific sigmaD factor, sigD. Sequence and primer extension data demonstrate that a PA promoter immediately upstream of flgB, henceforth referred to as the fla/che PA, and the PD-3 promoter are active in vivo. Transcription from the PD-3 element is dependent on sigmaD activity and is regulated by the flagellum-specific negative regulator, FlgM. In a strain containing a deletion of fla/che PA (PADelta), sigmaD protein was not detected, demonstrating that the fla/che PA is necessary for wild-type expression of the sigD gene. Thus, sigD is part of the >26-kb fla/che operon. Consistent with a lack of detectable sigmaD protein, the PADelta strain grows as long filaments and does not express a sigmaD-dependent hag::lacZ reporter construct. These phenotypes are indicative of a lack of sigD expression or complete inhibition of sigmaD activity by FlgM. However, sigmaD activity is found in a double mutant containing the PADelta and a null mutation in flgM. The double mutant no longer grows as long filaments, and expression of hag::lacZ is partially restored. These data demonstrate that a low level of sigmaD activity does exist in the PADelta mutant but can be detected only in the presence of a null mutation in flgM. Therefore, normal expression of sigD may also involve another promoter(s) within the fla/che operon.
Estacio
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W
Department of Biology, San Francisco State University, San Francisco, California 94132, USA.
Anna-Arriola
S S
SS
Adedipe
M
M
Márquez-Magaña
L M
LM
D001412:Bacillus subtilis / Q000235:genetics*; D001483:Base Sequence; D005408:Flagellin / Q000235:genetics*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics* / Q000502:physiology; D016415:Sequence Alignment; D014158:Transcription, Genetic
D005408:Flagellin; C416532:flaB flagellin