title: Mechanisms Underlying Adaptation to Life in Hydrogen Sulfide-Rich Environments.
abstract: Hydrogen sulfide (H2S) is a potent toxicant interfering with oxidative phosphorylation in mitochondria and creating extreme environmental conditions in aquatic ecosystems. The mechanistic basis of adaptation to perpetual exposure to H2S remains poorly understood. We investigated evolutionarily independent lineages of livebearing fishes that have colonized and adapted to springs rich in H2S and compared their genome-wide gene expression patterns with closely related lineages from adjacent, nonsulfidic streams. Significant differences in gene expression were uncovered between all sulfidic and nonsulfidic population pairs. Variation in the number of differentially expressed genes among population pairs corresponded to differences in divergence times and rates of gene flow, which is consistent with neutral drift driving a substantial portion of gene expression variation among populations. Accordingly, there was little evidence for convergent evolution shaping large-scale gene expression patterns among independent sulfide spring populations. Nonetheless, we identified a small number of genes that was consistently differentially expressed in the same direction in all sulfidic and nonsulfidic population pairs. Functional annotation of shared differentially expressed genes indicated upregulation of genes associated with enzymatic H2S detoxification and transport of oxidized sulfur species, oxidative phosphorylation, energy metabolism, and pathways involved in responses to oxidative stress. Overall, our results suggest that modification of processes associated with H2S detoxification and toxicity likely complement each other to mediate elevated H2S tolerance in sulfide spring fishes. Our analyses allow for the development of novel hypotheses about biochemical and physiological mechanisms of adaptation to extreme environments.
authors: School of Biological Sciences, Washington State University tobler@ksu.edu joanna.l.kelley@wsu.edu.
authors: Joanna L
authors: JL
authors: Kelley
authors: División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, Villahermosa, Tabasco, México.
authors: Lenin
authors: L
authors: Arias-Rodriguez
authors: Department of Genetics, Stanford University.
authors: Dorrelyn
authors: D
authors: Patacsil Martin
authors: Department of Plant Biology, Carnegie Institution for Science, Stanford, CA.
authors: Muh-Ching
authors: MC
authors: Yee
authors: Department of Genetics, Stanford University.
authors: Carlos D
authors: CD
authors: Bustamante
authors: Division of Biology, Kansas State University tobler@ksu.edu joanna.l.kelley@wsu.edu.
authors: Michael
authors: M
authors: Tobler
mesh_terms: D000064:Acclimatization / Q000235:genetics / Q000502:physiology; D000222:Adaptation, Physiological / Q000235:genetics / Q000502:physiology*; D000818:Animals; D005075:Biological Evolution; D017753:Ecosystem; D004777:Environment; D019143:Evolution, Molecular; D051456:Gene Flow; D005828:Genetics, Population / Q000379:methods; D016678:Genome; D006862:Hydrogen Sulfide / Q000378:metabolism*; D011036:Poecilia / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012641:Selection, Genetic; D016415:Sequence Alignment / Q000379:methods; D017423:Sequence Analysis, RNA / Q000379:methods; D059467:Transcriptome
chemical_list: D006862:Hydrogen Sulfide
keywords: H2S; Poecilia mexicana (Poeciliidae); RNA-sequencing.; ecological physiology; evolution; extreme environments; gene expression