Determinants and relative weight of genetic and epigenetic variation in the resistance of the oyster Crassostrea gigas to the Pacific Oyster Mortality Syndrome

• Main Author: Gawra, Janan
• Other Authors: Interactions Hôtes-Pathogènes-Environnements (IHPE), Université de Perpignan Via Domitia (UPVD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Université de Perpignan, Christoph Grunau, Jérémie Vidal-Dupiol
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2022
• Subjects: Oyster; Virus; Resistance/susceptibility; Host/pathogen; Genetic/epigenetic; Gwas/ewas; Huitre; Résistance/sensibilité; Hôte/pathogène; Génétique/épigéntique; [SDV.SA]Life Sciences [q-bio]/Agricultural sciences; [SDV.EE.IEO]Life Sciences [q-bio]/Ecology; environment/Symbiosis; Pacific; Crassostrea gigas; Pacific oyster
• Online Access: https://theses.hal.science/tel-03772638; https://theses.hal.science/tel-03772638/document; https://theses.hal.science/tel-03772638/file/These_Gawra_Janan_2022_Diffusion.pdf

Together with the increase of human population, there is a mathematical increase for food supply. Since 2008, mass mortality events of Pacific oysters (Crassostrea gigas) juveniles caused by the Pacific Oyster Mortality Syndrome (POMS) have threatened the oyster aquaculture industry. Studies on the resistance of C. gigas to POMS has demonstrated a genetic bases and more recently, it was shown to rely on early transcriptomic response to the viral infection. Although data about the involvement of epigenetics in POMS resistance are still scarce, the essential role of the transcriptome, from the basal level to the antiviral response, and the effect of environmental exposure on the resistance of oyster, collectively suggest that epigenetic can play an essential role. Here we propose a framework to study simultaneously the potential role of genetic and epigenetic in the expression of phenotype by using the C.gigas/POMS model at the natural population level. We developed an exome capture approach to obtain genetic (Single Nucleotide Polymorphisms; SNPs) and epigenetic (DNA methylation at CG context; CpGs) information. In the present thesis, the exome capture developed allowed us to capture the genetic and epigenetic variation on more than 65 % of the total exons. We showed that wild oyster populations differentially exposed to the POMS display signatures of selections both in their genome (SNPs) and in epigenome (CpGs). A high number of these SNPs and CpGs were located in genes involved in immune functions. These results confirmed that host population facing pathogen emergence could rely on genetic and epigenetic variation to rapidly adapt to emerging diseases. While our study confirms the essential role played by the DNA sequence it also shows that other mechanisms can interplay with this sequence to encode a resistant phenotype. However, they can also be independent from this DNA sequence and participate to the expressio n of resistance. These results confirm that holistic approaches of the resistance of host ...