Imd pathway is involved in the interaction of Drosophila melanogaster with the entomopathogenic bacteria, Xenorhabdus nematophila and Photorhabdus luminescens

Xenorhabdus nematophila/Steinernema carpocapsae and Photorhabdus luminescens/Heterorhabditis bacteriophora are nemato-bacterial complexes highly pathogenic for insects Using a syringe as artificial vector we have analyzed the effects of the two bacteria X nematophila and P luminescens on the genetic tool Insect Drosophila melanogaster Both bacteria were found to kill adult flies in a dose dependent manner with X nematophila being the fastest On the other hand when an injection of non-pathogenic bacteria Escherichia cob is performed 1 day before challenge with the entomopathogenic bacteria then the survival of Drosophila flies was prolonged by at least 20 h After injection of entomopathogenic bacteria Drosophila mutant Dif(1) affected on the Toll pathway showed a similar phenotype than wild-type flies whereas Drosophila mutant Dredd(D55) affected on the imd pathway was not protected by a prior injection of E coli This suggested that members of the imd pathway might be targets of these entomopathogenic bacteria albeit synthesis of antimicrobial peptides through this signaling pathway was Induced by X nematophila as well as P luminescens Finally P luminescens phoP mutant an avirulent mutant in the Lepidopteran insect Spodoptera littoral's was found poorly virulent for D melanogaster phoP mutant partially protected D melanogaster flies if injected 1 day before the injection of P luminescens wild-type TT01 to the same extent than the E coli-induced protection However phoP recovered a level of pathogenicity comparable to P luminescens wild-type TT01 when injected to Drosophila flies affected on the imd pathway (C) 2010 Elsevier Ltd All rights reserved