Species traits predict the aryl hydrocarbon receptor 1 (AHR1) subtypes responsible for dioxin sensitivity in birds

Kristin Bianchini,Christy A. Morrissey

doi:10.1038/s41598-020-68497-y

Kristin Bianchini, Christy A. Morrissey

Open Access

https://doi.org/10.1038/s41598-020-68497-y

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Abstract

Differences in avian sensitivity to dioxin-like compounds (DLCs) are directly attributable to the identities of amino acids at two sites within the ligand binding domain (LBD) of the aryl hydrocarbon receptor 1 (AHR1). Recent work suggests that by influencing avian exposure to naturally occurring dioxins, differences in diet, habitat, and migration may have influenced the evolution of three AHR1 LBD genotypes in birds: type 1 (high sensitivity), type 2 (moderate sensitivity), and type 3 (low sensitivity). Using a boosted regression tree (BRT) analysis, we built on previous work by examining the relationship between a comprehensive set of 17 species traits, phylogeny, and the AHR1 LBD across 89 avian species. The 17 traits explained a combined 74% of the model deviance, while phylogenetic relatedness explained only 26%. The strongest predictors of AHR1 LBD were incubation period and habitat type. We found that type 3 birds tended to occupy aquatic habitats, and, uniquely, we also found that type 3 birds tended to have slower developmental rates. We speculate that this reflects higher evolutionary exposure to naturally occurring dioxins in waterbirds and species with K-selected life histories. This study highlights the value of trait-based approaches in helping to understand differing avian species sensitivities to environmental contaminants.

Highlights

Dioxin-like compounds (DLCs) are environmental contaminants of great ecotoxicological concern
Previous work has established that differences in avian dioxin-like compounds (DLCs) sensitivity are directly related to the identity of amino acids at sites 324 and 380 within the ligand-binding domain (LBD) of the aryl hydrocarbon receptor 1 (AHR1)[10,11,13], and differences in amino acid residues at other sites do not contribute to inter-species variations in DLC sensitivity[13]
This study presents an exploratory trait-based analysis examining the relationship between 17 biological and ecological traits, phylogeny, and the 13 avian AHR1 LBD subtypes across a large sample of 89 bird species

Summary

Introduction

Dioxin-like compounds (DLCs) are environmental contaminants of great ecotoxicological concern. When DLCs or other ligands bind to the AHR, the AHR translocates to the nucleus, where it forms a heterodimer with the aryl hydrocarbon receptor translocator (ARNT). This interaction allows the AHR to bind the dioxin-responsive element, a promoter element of xenobiotic-metabolizing enzymes such as cytochrome P4501A (CYP1A). Previous work has established that differences in avian DLC sensitivity are directly related to the identity of amino acids at sites 324 and 380 within the ligand-binding domain (LBD) of the aryl hydrocarbon receptor 1 (AHR1)[10,11,13], and differences in amino acid residues at other sites do not contribute to inter-species variations in DLC sensitivity[13]. The use of traits in ecotoxicological research is relatively limited to invertebrate species[20]

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