Mutational Analysis of Volatile Oxylipins in a Eclosion Assay.

is a ubiquitous opportunistic pathogen. We have previously reported that volatile organic compounds (VOCs) produced by cause delays in metamorphosis, morphological abnormalities, and death in a eclosion model. Here, we developed . deletion mutants with blocked oxylipin biosynthesis pathways (∆) and then exposed the third instar larvae of to a shared atmosphere with either wild-type or oxylipin mutant cultures for 15 days. Fly larvae exposed to VOCs from wild-type . strains exhibited delays in metamorphosis and toxicity, while larvae exposed to VOCs from the ∆ mutant displayed fewer morphogenic delays and higher eclosion rates than the controls. In general, when fungi were pre-grown at 37 °C, the effects of the VOCs they produced were more pronounced than when they were pre-grown at 25 °C. GC-MS analysis revealed that the wild-type Af293 produced more abundant VOCs at higher concentrations than the oxylipin-deficient strain Af293∆ did. The major VOCs detected from wild-type Af293 and its triple mutant included isopentyl alcohol, isobutyl alcohol, 2-methylbutanal, acetoin, and 1-octen-3-ol. Unexpectedly, compared to wild-type flies, the eclosion tests yielded far fewer differences in metamorphosis or viability when flies with immune-deficient genotypes were exposed to VOCs from either wild-type or ∆ oxylipin mutants. In particular, the toxigenic effects of VOCs were not observed in mutant flies deficient in the Toll () pathway. These data indicate that the innate immune system of mediates the toxicity of fungal volatiles, especially via the Toll pathway.