Lack of an antibacterial response defect in Drosophila Toll-9 mutant

PLoS One. 2011 Feb 28;6(2):e17470. doi: 10.1371/journal.pone.0017470.


Toll and Toll-like receptors represent families of receptors involved in mediating innate immunity response in insects and mammals. Although Drosophila proteome contains multiple Toll paralogs, Toll-1 is, so far, the only receptor to which an immune role has been attributed. In contrast, every single mammalian TLR is a key membrane receptor upstream of the vertebrate immune signaling cascades. The prevailing view is that TLR-mediated immunity is ancient. Structural analysis reveals that Drosophila Toll-9 is the most closely related to vertebrate TLRs and utilizes similar signaling components as Toll-1. This suggests that Toll-9 could be an ancestor of TLR-like receptors and could have immune function. Consistently, it has been reported that over-expression of Toll-9 in immune tissues is sufficient to induce the expression of some antimicrobial peptides in flies. These results have led to the idea that Toll-9 could be a constitutively active receptor that maintain significant levels of antimicrobial molecules and therefore provide constant basal protection against micro-organisms. To test theses hypotheses, we generated and analyzed phenotypes associated with a complete loss-of-function allele of Toll-9. Our results suggest that Toll-9 is neither required to maintain a basal anti-microbial response nor to mount an efficient immune response to bacterial infection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging / genetics
  • Aging / immunology
  • Animals
  • Animals, Genetically Modified
  • Antimicrobial Cationic Peptides / metabolism
  • Bacteria / immunology*
  • Drosophila / genetics*
  • Drosophila / immunology*
  • Drosophila Proteins / genetics*
  • Drosophila Proteins / physiology
  • Female
  • Gene Knockout Techniques
  • Hemocytes / cytology
  • Immunity, Innate / genetics*
  • Male
  • Toll-Like Receptors / genetics*
  • Toll-Like Receptors / physiology
  • alpha-Defensins / metabolism


  • Antimicrobial Cationic Peptides
  • Drosophila Proteins
  • Toll-9 protein, Drosophila
  • Toll-Like Receptors
  • alpha-Defensins