title: Analysis of cryIAa expression in sigE and sigK mutants of Bacillus thuringiensis.
abstract: The sigE and sigK genes, encoding the sporulation-specific sigma factors sigma 35 and sigma 28 of Bacillus thuringiensis, were each disrupted by inserting a gene conferring resistance to kanamycin into their coding sequences. The B. thuringiensis SigE- and sigK- mutant strains were blocked at different sporulation stages and were unable to sporulate. The SigE-strain was blocked at stage II of sporulation, whereas the SigK- strain was blocked at stage IV. The expression of a cryIAa'-'lacZ transcriptional fusion was analysed in these genetic backgrounds and it was found that both sigma factors are involved in the in vivo transcription of this gene. However, the SigK- strain harbouring the cryIAa gene produced amounts of toxin similar to those produced by the B. thuringiensis Spo+ strain. The toxins accumulated in the mother cell compartment to form a crystal inclusion which remained encapsulated within the cell wall. Thus, transcription from the sigma E-dependent promoter alone (Bt I promoter) is sufficient to support high levels of toxin production in B. thuringiensis.
authors.affiliation: Unité de Biochimie Microbienne, Centre National de la Recherche Scientifique URA 1300, Institut Pasteur, Paris, France.
authors.forename: A
authors.initials: A
authors.lastname: Bravo
authors.forename: H
authors.initials: H
authors.lastname: Agaisse
authors.forename: S
authors.initials: S
authors.lastname: Salamitou
authors.forename: D
authors.initials: D
authors.lastname: Lereclus
mesh_terms: D001413:Bacillus thuringiensis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D004731:Endotoxins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D006460:Hemolysin Proteins; D007612:Kanamycin / Q000494:pharmacology; D007763:Lac Operon; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010572:Pest Control, Biological; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012808:Sigma Factor / Q000235:genetics* / Q000502:physiology; D013171:Spores, Bacterial / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic / Q000235:genetics; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D017931:DNA Primers; D004731:Endotoxins; C064971:FliA protein, Bacteria; D006460:Hemolysin Proteins; D011993:Recombinant Fusion Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C030956:insecticidal crystal protein, Bacillus Thuringiensis; C063202:sporulation-specific sigma factors; D007612:Kanamycin; D001616:beta-Galactosidase