Molecular and General Genetics MGG

, Volume 250, Issue 6, pp 734–741 | Cite as

Analysis of cryIAa expression in sigE and sigK mutants of Bacillus thuringiensis

  • A. Bravo
  • Hervé Agaisse
  • Sylvie Salamitou
  • D. Lereclus
ORIGINAL PAPER

Abstract

 The sigE and sigK genes, encoding the sporulation-specific sigma factors σ35 and σ28 of Bacillus thuringiensis, were each disrupted by inserting a gene conferring resistance to kanamycin into their coding sequence. 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 σE-dependent promoter alone (Bt I promoter) is sufficient to support high levels of toxin production in B. thuringiensis.

Key words Bacillus thuringiensis cry gene expression Encapsulation Sigma factors Sporulation 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1996

Authors and Affiliations

  • A. Bravo
    • 1
  • Hervé Agaisse
    • 1
  • Sylvie Salamitou
    • 1
  • D. Lereclus
    • 1
  1. 1.Unité de Biochimie Microbienne, Centre National de la Recherche Scientifique URA 1300, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris cedex 15, FranceFR

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