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The nuclear hormone receptor NHR-86 controls anti-pathogen responses in C. elegans [ChIP-seq]

ABSTRACT: Germline-encoded pattern recognition receptors (e.g. Toll-like receptors) play key roles in innate immune activation. However, some metazoans, such as C. elegans, do not have canonical mechanisms of pattern recognition, yet they are able to mount anti-pathogen immune defenses. Here, we demonstrate that a nuclear hormone receptor (NHR), a ligand-gated transcription factor, functions in immune activation and pathogen defense. NHRs have expanded dramatically in C. elegans compared to other metazoans. Because NHRs often function redundantly, it has been challenging experimentally to characterize the biology of individual NHRs. Here, we use genetic epistasis experiments, transcriptome profiling analyses and chromatin immunoprecipitation to show NHR-86 is sufficient to activate protective immune defenses against the bacterial pathogen Pseudomonas aeruginosa. Interestingly, NHR-86 drives the transcription of immune effectors whose basal regulation requires the canonical p38 MAPK PMK-1 immune pathway. However, NHR-86 functions independently of PMK-1 and directly induces the transcription of infection response genes in a manner that confers protection from bacterial infection. Importantly, we found that nhr-86 does control immune gene expression and is necessary for host defense against a different pathogen, Enterococcus faecalis. Our findings characterize an ancient role of an NHR in innate immunity, and suggest that the expansion of the NHR protein family in C. elegans has been fueled in part by the need to activate immune defenses in response to pathogen attack.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE117719 | GEO | 2019/01/09

REPOSITORIES: GEO

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Project description:Acyl-coA synthases (ACSs) produce fatty acyl-CoAs that are used in metabolic and signaling pathways. Metazoans have a large number of ACS genes with differing expression patterns and substrate preferences, but the physiological roles of most ACS genes are unknown. Here, we focused on the C. elegans acyl CoA synthase, ACS-3, which is known to regulate fat uptake and de novo fat synthesis through the conserved nuclear hormone receptor, nhr-25. We performed microarray analysis of acs-3 mutants to elucidate the acs-3-regulated transcription program. This analysis revealed an enrichment among differentially regulated genes of those involved in lipid metabolism, pathogen and wounding responses, and sterol binding genes, among others. As the immunity genes were the most represented gene class, we performed pathogen sensitivity assays to test the phenotypic consequences of this immune gene regulation. Interestingly, acs-3 mutants were hypersensitive to the fungal pathogen D. coniospora, but only mildly sensitive to the bacterial pathogen P. aeruginosa. acs-3 mutation suppressed nhr-25 mutant sensitivity to P. aeruginosa, yet surprisingly microarray analysis of nhr-25(RNAi) animals revealed significant overlap with the acs-3 mutant transcriptome, with an enrichment of pathogen response genes. The upregulation of pathogen response genes in acs-3(ft5) mutants and following nhr-25 reduction-of-function (rf) does not appear to be due to a constitutive osmotic response or defective cuticle barrier, two potential explanations for the acs-3(ft5) and nhr-25(rf) expression of innate immunity genes in the absence of pathogen exposure. Together, these data indicate that ACS-3 promotes resistance to the fungal pathogen, D. coniospora and regulates innate immunity genes through an unknown mechanism. Potential roles for ACS-3 in innate immunity are discussed. We used two-color expression microarrays to compare the transcriptional profiles in two experimental conditions: 1) comparing wild-type (N2) L4 stage larval worms to acs-3(ft5) L4 larval mutant animals; and 2) animals grown to L4 larval stage on bacteria harboring vectors for either control or nhr-25 RNA-interference (RNAi). L4 stage was determined by morphology of the developing vulva. Three biological replicates were used for each experimental condition. Statistically significant changes in gene expression in each experimental were determined using M-bM-^@M-^\linear models for microarray dataM-bM-^@M-^] (limma).

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The nuclear hormone receptor NHR-86 controls anti-pathogen responses in C. elegans [ChIP-seq]

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