Project description:Marine intertidal organisms commonly face hypoxic stress during low tide emersion; moreover, eutrophic conditions and sediment nearness could lead to hypoxic phenomena; it is indeed important to understand the molecular processes involved in the response to hypoxia. In this study the molecular response of the Pacific oyster Crassostrea gigas to prolonged hypoxia (2 mg O2 L-1 for 20 d) was investigated under experimental conditions. A transcriptomic approach was employed using a cDNA microarray of 9058 C. gigas clones to highlight the genetic expression patterns of the Pacific oyster under hypoxic conditions. Lines of oysters resistant (R) and susceptible (S) to summer mortality were used in this study. This is the first study employing microarrays to characterize the genetic markers and metabolic pathways responding to hypoxic stress in C. gigas.
Project description:Summer mortality of the Pacific oyster Crassostrea gigas is the result of a complex interaction between oysters, their environment and pathogens. Heredity appears to be a major factor determining the sensitivity of oysters to summer mortality, allowing resistant (R) and susceptible (S) lines to be produced. We conducted genome-wide expression profiling of R and S gonads during the 3-month period preceding a summer mortality event using a 9K cDNA microarray that we designed. This transcriptional analysis provides new indications to define markers for Quantitative Trait Loci searches and functional studies, and evaluates the potential role of each gene in the resistance to summer mortality
Project description:The cultivated Pacific oyster Crassostrea gigas has suffered for decades large scale summer mortality phenomenon resulting from the interaction between the environment parameters, the oyster physiological and/or genetic status and the presence of pathogenic microorganisms including Vibrio species. To obtain a general picture of the molecular mechanisms implicated in C. gigas immune responsiveness to circumvent Vibrio infections, we have developed the first deep sequencing study of the transcriptome of hemocytes, the immunocompetent cells. Using Digital Gene Expression (DGE), we generated a transcript catalog of up-regulated genes from oysters surviving infection with virulent Vibrio strains (Vibrio splendidus LGP32 and V. aestuarianus LPi 02/41) compared to an avirulent one, V. tasmaniensis LMG 20012(T). For that an original experimental infection protocol was developed in which only animals that were able to survive infections were considered for the DGE approach. We report the identification of cellular and immune functions that characterize the oyster capability to survive pathogenic Vibrio infections. Functional annotations highlight genes related to signal transduction of immune response, cell adhesion and communication as well as cellular processes and defence mechanisms of phagocytosis, actin cytosqueleton reorganization, cell trafficking and autophagy, but also antioxidant and anti-apoptotic reactions. In addition, quantitative PCR analysis reveals the first identification of pathogen-specific signatures in oyster gene regulation, which opens the way for in depth molecular studies of oyster-pathogen interaction and pathogenesis. This work is a prerequisite for the identification of those physiological traits controlling oyster capacity to survive a Vibrio infection and, subsequently, for a better understanding of the phenomenon of summer mortality. 4 Samples.
Project description:Low salinity is one of the main factors limiting the distribution and survival of marine species. As a euryhaline species, the Pacific oyster Crassostrea gigas can be tolerant to relative low salinity. Through Illumina sequencing, we generated two transcriptomes with samples taken from gills of oysters exposed to the low salinity seawater versus the optimal seawater. By RNAseq technology, we found 1665 up-regulation genes and 1815 down-regulation genes that may regulate osmotic stress in C. gigas. As blasted by GO annotation and KEGG pathway mapping, functional annotation of the genes recovered diverse biological functions and processes. The genes regulated significantly were dominated in cellular process and regulation of biological process, intracellular and cell, binding and protein binding according to GO annotation. The results highlight genes related to osmoregulation and signaling and interactions of osmotic stress response, anti-apoptotic reactions as well as immune response, cell adhesion and communication, cytosqueleton and cell cycle. The study aimed to compare the expression data of the two transcriptomes to provide some useful insights into signal transduction pathways in oysters and offer a number of candidate genes as potential markers of tolerance to hypoosmotic stress for oysters. In addition, the characterization of C. gigas transcriptome will facilitate research into biological processes underlying physiological adaptations to hypoosmotic shock for marine invertebrates. Twelve Pacific oysters were exposed in low salinity (8‰) seawater and in optimal salinity (25‰) seawater, respectively. Gills from six oysters in each condition were balanced mixed respectively. The transcriptomes of two samples were generated by deep sequencing, using Illumina HiSeq2000.
Project description:The cultivated Pacific oyster Crassostrea gigas has suffered for decades large scale summer mortality phenomenon resulting from the interaction between the environment parameters, the oyster physiological and/or genetic status and the presence of pathogenic microorganisms including Vibrio species. To obtain a general picture of the molecular mechanisms implicated in C. gigas immune responsiveness to circumvent Vibrio infections, we have developed the first deep sequencing study of the transcriptome of hemocytes, the immunocompetent cells. Using Digital Gene Expression (DGE), we generated a transcript catalog of up-regulated genes from oysters surviving infection with virulent Vibrio strains (Vibrio splendidus LGP32 and V. aestuarianus LPi 02/41) compared to an avirulent one, V. tasmaniensis LMG 20012(T). For that an original experimental infection protocol was developed in which only animals that were able to survive infections were considered for the DGE approach. We report the identification of cellular and immune functions that characterize the oyster capability to survive pathogenic Vibrio infections. Functional annotations highlight genes related to signal transduction of immune response, cell adhesion and communication as well as cellular processes and defence mechanisms of phagocytosis, actin cytosqueleton reorganization, cell trafficking and autophagy, but also antioxidant and anti-apoptotic reactions. In addition, quantitative PCR analysis reveals the first identification of pathogen-specific signatures in oyster gene regulation, which opens the way for in depth molecular studies of oyster-pathogen interaction and pathogenesis. This work is a prerequisite for the identification of those physiological traits controlling oyster capacity to survive a Vibrio infection and, subsequently, for a better understanding of the phenomenon of summer mortality.
Project description:Massive mortalities have been observed in France since 2008 on spat and juvenile Pacific oysters, Crassostrea gigas. A herpes virus called OsHV-1, easily detectable by PCR, has been implicated in the mortalities as demonstrated by the results of numerous field studies linking mortality with OsHV-1 prevalence. Moreover, experimental infections using viral particles have documented the pathogenicity of OsHV-1. The physiological responses of host to pathogen are not well known. In this study, a number of genes involved in the response to viral challenge have been identified and can be considered as confirmation of the role of the virus in the observed mortality. The aim of this study was to understand mechanisms brought into play against the virus during infection in the field. A microarray assay has been developed for a major part of the oyster genome and used for studying the host transcriptome. Spat with and without detectable OsHV-1 infection were compared by microarray during mortality episodes. The result allowed establishment of a hypothetic scheme of the host cell’s infection by, and response to, the pathogen. This response seems to be different to “sensu stricto” innate immunity through genic regulation of the virus life cycle. . Some regulatory response against the virus may explain that some oysters are able to survive infection by regulation of the viral genes associated with the OsHV-1 life cycle.
Project description:Low salinity is one of the main factors limiting the distribution and survival of marine species. As a euryhaline species, the Pacific oyster Crassostrea gigas can be tolerant to relative low salinity. Through Illumina sequencing, we generated two transcriptomes with samples taken from gills of oysters exposed to the low salinity seawater versus the optimal seawater. By RNAseq technology, we found 1665 up-regulation genes and 1815 down-regulation genes that may regulate osmotic stress in C. gigas. As blasted by GO annotation and KEGG pathway mapping, functional annotation of the genes recovered diverse biological functions and processes. The genes regulated significantly were dominated in cellular process and regulation of biological process, intracellular and cell, binding and protein binding according to GO annotation. The results highlight genes related to osmoregulation and signaling and interactions of osmotic stress response, anti-apoptotic reactions as well as immune response, cell adhesion and communication, cytosqueleton and cell cycle. The study aimed to compare the expression data of the two transcriptomes to provide some useful insights into signal transduction pathways in oysters and offer a number of candidate genes as potential markers of tolerance to hypoosmotic stress for oysters. In addition, the characterization of C. gigas transcriptome will facilitate research into biological processes underlying physiological adaptations to hypoosmotic shock for marine invertebrates.
Project description:Massive mortalities have been observed in France since 2008 on spat and juvenile Pacific oysters, Crassostrea gigas. A herpes virus called OsHV-1, easily detectable by PCR, has been implicated in the mortalities as demonstrated by the results of numerous field studies linking mortality with OsHV-1 prevalence. Moreover, experimental infections using viral particles have documented the pathogenicity of OsHV-1. The physiological responses of host to pathogen are not well known. In this study, a number of genes involved in the response to viral challenge have been identified and can be considered as confirmation of the role of the virus in the observed mortality. The aim of this study was to understand mechanisms brought into play against the virus during infection in the field. A microarray assay has been developed for a major part of the oyster genome and used for studying the host transcriptome. Spat with and without detectable OsHV-1 infection were compared by microarray during mortality episodes. The result allowed establishment of a hypothetic scheme of the host cell’s infection by, and response to, the pathogen. This response seems to be different to “sensu stricto” innate immunity through genic regulation of the virus life cycle. . Some regulatory response against the virus may explain that some oysters are able to survive infection by regulation of the viral genes associated with the OsHV-1 life cycle. Gene expression was measured from four individual animals of three sites, an oyster production area where mortalities on spat was observed in Spring (BL: Blainville sur mer) and two sanctuary sites (CRIC, Cricqueville en Bessin without production and CAB, an offshore storage structure)