title: High polymorphism in big defensin gene expression reveals presence-absence gene variability (PAV) in the oyster Crassostrea gigas.
abstract: We report here the first evidence in an invertebrate, the oyster Crassostrea gigas, of a phenomenon of Presence-Absence Variation (PAV) affecting immune-related genes. We previously evidenced an extraordinary interindividual variability in the basal mRNA abundances of oyster immune genes including those coding for a family of antimicrobial peptides, the big defensins (Cg-BigDef). Cg-BigDef is a diverse family composed of three members: Cg-BigDef1 to -3. Here, we show that besides a high polymorphism in Cg-BigDef mRNA expression, not all individual oysters express simultaneously the three Cg-BigDefs. Moreover, in numerous individuals, no expression of Cg-BigDefs could be detected. Further investigation at the genomic level revealed that in individuals in which the transcription of one or all Cg-BigDefs was absent the corresponding Cg-bigdef gene was missing. In our experiments, no correlation was found between Cg-bigdef PAV and oyster capacity to survive Vibrio infections. The discovery of P-A immune genes in oysters leads to reconsider the role that the immune system plays in the individual adaptation to survive environmental, biotic and abiotic stresses.
authors.affiliation: Ifremer, CNRS, Université Montpellier 2, IRD, Université Montpellier 1, UMR5119 - Ecology of Coastal Marine Systems, Place Eugène Bataillon, CC80, 34095 Montpellier, France. Electronic address: rafael.d.rosa@ufsc.br.
authors.forename: Rafael D
authors.initials: RD
authors.lastname: Rosa
authors.affiliation: Ifremer, CNRS, Université Montpellier 2, IRD, Université Montpellier 1, UMR5119 - Ecology of Coastal Marine Systems, Place Eugène Bataillon, CC80, 34095 Montpellier, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Alonso
authors.affiliation: Ifremer, CNRS, Université Montpellier 2, IRD, Université Montpellier 1, UMR5119 - Ecology of Coastal Marine Systems, Place Eugène Bataillon, CC80, 34095 Montpellier, France.
authors.forename: Adrien
authors.initials: A
authors.lastname: Santini
authors.affiliation: Ifremer, CNRS, Université Montpellier 2, IRD, Université Montpellier 1, UMR5119 - Ecology of Coastal Marine Systems, Place Eugène Bataillon, CC80, 34095 Montpellier, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Vergnes
authors.affiliation: Ifremer, CNRS, Université Montpellier 2, IRD, Université Montpellier 1, UMR5119 - Ecology of Coastal Marine Systems, Place Eugène Bataillon, CC80, 34095 Montpellier, France.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Bachère
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics* / Q000276:immunology*; D001483:Base Sequence; D049896:Crassostrea / Q000276:immunology*; D023082:Defensins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014733:Vibrio / Q000276:immunology; D014735:Vibrio Infections / Q000276:immunology* / Q000382:microbiology
chemical_list: D023181:Antimicrobial Cationic Peptides; D023082:Defensins
keywords: Antimicrobial peptide; Gene copy number variation; High-throughput microfluidic RT-qPCR; Mollusk bivalve; Polymorphism; Vibrio infection