Mercado, M.P. et al. (2019) International Worm Meeting "Natural variation in WAH-1/AIF regulates the response to prolonged oxidative stress in Caenorhabditis elegans."

Fraser, A.G., Mercado, M.P.

[International Worm Meeting, 2019]

In an era of prevalent anthelmintic resistance, there is a growing need for novel drug targets that are selective for parasitic helminths. These parasites can survive extended periods of hypoxia within their host through alternative metabolic pathways, and the resulting anaerobic metabolism offers a promising avenue for identifying novel targets. While we are unable to screen through parasitic helminths at high throughput, the free-living nematode Caenorhabditis elegans also utilizes this alternative anaerobic metabolism when treated with cyanide (KCN), and has an extensive genetic toolkit that can be used for interrogation into specific pathways. Here, we use a panel of wild C. elegans isolates from the CeNDR collection and a high-throughput movement assay to detect loci underlying the response to recovery from prolonged exposure to KCN. Preliminary results have shown that wild strains of C. elegans vary in their ability to recover from KCN-induced paralysis, and initial GWAS analyses on a subset of isolates resulted in a single quantitative trait locus (QTL) on the right arm of chromosome III. The QTL confidence interval spans from 11.9 to12.6 Mb, containing 124 genes; 116 of which contain protein coding variants. To identify the causal gene within this interval, RNAi knockdown was utilized to recapitulate the hyper-recovery that was observed in the divergent isolates. The knockdown of wah-1, the C. elegans orthologue of the mammalian gene AIF, resulted in increased recovery following KCN exposure. WAH-1/AIF is a FAD-containing NADH-dependent oxidoreductase, and is known to be a regulator of mitochondrial oxidative phosphorylation. WAH-1/AIF is also necessary for proper mitochondrial morphology and the biogenesis of various respiratory complexes. Previous studies have shown that decreased expression of wah-1 lowers endogenous ROS levels, lowers complex I protein levels, and induces a nuclear-encoded mitochondrial stress response. Despite its evolutionarily conserved role in mitochondrial maintenance, our results suggest that variation in wah-1 activity affects survival in anaerobic conditions.

G Alloing et al. (1999) International C. elegans Meeting "Analysis of C. elegans host defense response to bacterial pathogen Pseudomonas aeruginosa"

M Tan, S Mahajan-Miklos, FM Ausubel, R Feinbaum, G Alloing

[International C. elegans Meeting, 1999]

Pathogenic bacteria are one of the major causes of disease in both animals and plants. Despite the specificity of the interaction between a bacterial pathogen and its host, there appear to be a number of common mechanisms underlying the process of disease (1,2). On the host side, it has been demonstrated that plants and animals share a set of defense mechanisms involved in "innate immunity". A signal transduction pathway with similarity to the Drosophila developmental regulatory Toll pathway appears to be critical for innate immunity in flies, mammals and plants (1). The underlying similarities between host/bacterial pathogen interactions suggested that a genetically tractable host/pathogen model could greatly improve our understanding of bacterial diseases in mammalian systems. A host/pathogen model system has been developed utilizing C. elegans and PA14, a clinical isolate of P. aeruginosa that is also virulent in Arabidopsis and mouse models. Depending on the medium used for bacterial growth, PA14 kills worms within 24 hours (Fast Killing or FK) or after a few days (Slow Killing or SK). FK is mediated at least in part by diffusible toxins whereas SK requires an infection-like process (3,4). Characterization of several PA14 mutants that are less pathogenic showed that the two killing processes require different bacterial virulence factors. We are interested in understanding the host response to infection by PA14. Towards this end, we have identified the C. elegans homologs of the Drosophila Toll receptor and Pelle kinase and are studying the role of these proteins in response to PA14 in both FK and SK. In addition, six C. elegans mutants have been isolated that are resistant to FK. We are beginning to map and characterize these mutants. (1) Belvin M.P. and Anderson K.V. (1996) Ann. Rev. Cell Dev. Biol. 12 , 393-416 (2) Finlay B.B and S. Falkow, S. (1997). Mol. Biol. Microbiol. Rev. 61 , 136-169 (3) Mahajan-Miklos, S. et al (1999). Cell 96 , 47-56 (4) Tan, M.-W. et al (1999). PNAS 96 , p715-720