Eight‐carbon volatiles are more toxic to wild‐type Drosophila melanogaster than to flies with blocked immune system mutations

Abstract

AbstractPrevious work using a Drosophila melanogaster Meigen (Diptera: Drosophilidae) bioassay suggested that the innate immune response of the fly might contribute to the toxicity of certain fungal volatile organic compounds (VOCs). Here, we exposed wild‐type or immune‐deficient strains (NOS, Imd, and Toll) of Drosophila male adults to two concentrations (0.02 and 0.1 µmol ml‐1) of volatilized chemical standards of 1‐octen‐3‐ol, 3‐octanone, and 3‐octanol, and their viability was monitored for 24 h. All fly strains were killed within 2 h when exposed to 1‐octen‐3‐ol at 0.1 µmol ml‐1. The wild‐type, red‐eyed (OregonR) strain was more resistant to all three compounds at both concentrations than the white‐eyed strain (w1118) with wild‐type immune genes. Of the three compounds tested, 3‐octanol at 0.02 µmol ml‐1 was the least toxic to all Drosophila strains. Of the white‐eyed fly mutants, the NOS mutant was more resistant to VOC exposure than the white‐eyed strains carrying no defects in the immune system. The white‐eyed RelE20 (Imd) mutant flies were more susceptible to 0.02 µmol ml‐1 of 1‐octen‐3‐ol than the red‐eyed spz6 (Toll) mutants. Unexpectedly, the most resistant to the eight‐carbon (8‐C) volatiles was displayed by double mutant flies carrying blocked immune system mutations in both the Imd and Toll pathways (RelE20spz6). These data suggest that components of the wild‐type innate immune system of Drosophila are responsible for causing death in flies exposed to 8‐C volatiles.