Embryonic gene expression of Coregonus palaea (whitefish) under pathogen stress as analyzed by high-throughput RNA-sequencing.
Most fishes produce free-living embryos that are exposed to environmental stressors immediately following fertilization, including pathogenic microorganisms. Initial immune protection of embryos involves the chorion, as a protective barrier, and maternally-allocated antimicrobial compounds. At later developmental stages, host-genetic effects influence susceptibility and tolerance, suggesting a direct interaction between embryo genes and pathogens. So far, only a few host genes could be identified that correlate with embryonic survival under pathogen stress in salmonids. Here, we utilized high-throughput RNA-sequencing in order to describe the transcriptional response of a non-model fish, the Alpine whitefish Coregonus palaea, to infection, both in terms of host genes that are likely manipulated by the pathogen, and those involved in an early putative immune response. Embryos were produced in vitro, raised individually, and exposed at the late-eyed stage to a virulent strain of the opportunistic fish pathogen Pseudomonas fluorescens. The pseudomonad increased embryonic mortality and affected gene expression substantially. For example, essential, upregulated metabolic pathways in embryos under pathogen stress included ion binding pathways, aminoacyl-tRNA-biosynthesis, and the production of arginine and proline, most probably mediated by the pathogen for its proliferation. Most prominently downregulated transcripts comprised the biosynthesis of unsaturated fatty acids, the citrate cycle, and various isoforms of b-cell transcription factors. These factors have been shown to play a significant role in host blood cell differentiation and renewal. With regard to specific immune functions, differentially expressed transcripts mapped to the complement cascade, MHC class I and II, TNF-alpha, and T-cell differentiation proteins. The results of this study reveal insights into how P. fluorescens impairs the development of whitefish embryos and set a foundation for future studies investigating host pathogen interactions in fish embryos.
Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland. Electronic address: laetitia.wilkins@unil.ch.
Laetitia G E
LG
Wilkins
Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland.
Emily S
ES
Clark
Fasteris SA, 1228 Plan-les-Ouates, Switzerland.
Laurent
L
Farinelli
Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland.
Claus
C
Wedekind
Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland.
Luca
L
Fumagalli
D056704:Adaptive Immunity; D000818:Animals; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000276:immunology / Q000378:metabolism; D005393:Fish Diseases / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D059014:High-Throughput Nucleotide Sequencing / Q000662:veterinary; D011552:Pseudomonas Infections / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D011551:Pseudomonas fluorescens / Q000502:physiology*; D012487:Salmonidae; D017422:Sequence Analysis, DNA; D059467:Transcriptome
D016207:Cytokines; D029941:Fish Proteins
Coregonus palaea; Embryonic development; Gene expression; Pathogen infection; Pseudomonas fluorescens; Whitefish