@article {3779, title = {Immune and Stress Responses in Oysters with Insights on Adaptation.}, journal = {Fish Shellfish Immunol}, year = {2015}, month = {2015 May 16}, abstract = {

Oysters are representative bivalve molluscs that are widely distributed in world oceans. As successful colonizers of estuaries and intertidal zones, oysters are remarkably resilient against harsh environmental conditions including wide fluctuations in temperature and salinity as well as prolonged air exposure. Oysters have no adaptive immunity but can thrive in microbe-rich estuaries as filter-feeders. These unique adaptations make oysters interesting models to study the evolution of host-defense systems. Recent advances in genomic studies including sequencing of the oyster genome have provided insights into oyster{\textquoteright}s immune and stress responses underlying their amazing resilience. Studies show that the oyster genomes are highly polymorphic and complex, which may be key to their resilience. The oyster genome has a large gene repertoire that is enriched for immune and stress response genes. Thousands of genes are involved in oyster{\textquoteright}s immune and stress responses, through complex interactions, with many gene families expanded showing high sequence, structural and functional diversity. The high diversity of immune receptors and effectors may provide oysters with enhanced specificity in immune recognition and response to cope with diverse pathogens in the absence of adaptive immunity. Some members of expanded immune gene families have diverged to function at different temperatures and salinities or assumed new roles in abiotic stress response. Most canonical innate immunity pathways are conserved in oysters and supported by a large number of diverse and often novel genes. The great diversity in immune and stress response genes exhibited by expanded gene families as well as high sequence and structural polymorphisms may be central to oyster{\textquoteright}s adaptation to highly stressful and widely changing environments.

}, issn = {1095-9947}, doi = {10.1016/j.fsi.2015.05.018}, author = {Guo, Ximing and He, Yan and Zhang, Linlin and Christophe Lelong and Jouaux, Aude} } @article {3828, title = {Transcriptome analysis reveals strong and complex antiviral response in a mollusc.}, journal = {Fish Shellfish Immunol}, year = {2015}, month = {2015 May 22}, abstract = {

Viruses are highly abundant in the oceans, and how filter-feeding molluscs without adaptive immunity defend themselves against viruses is not well understood. We studied the response of a mollusc Crassostrea gigas to Ostreid herpesvirus 1 {\textmu}Var (OsHV-1μVar) infections using transcriptome sequencing. OsHV-1μVar can replicate extremely rapidly after challenge of C.\ gigas as evidenced by explosive viral transcription and DNA synthesis, which peaked at 24 and 48\ h post-inoculation, respectively, accompanied by heavy oyster mortalities. At 120\ h post-injection, however, viral gene transcription and DNA load, and oyster mortality, were greatly reduced indicating an end of active infections and effective control of viral replication in surviving oysters. Transcriptome analysis of the host revealed strong and complex responses involving the activation of all major innate immune pathways that are equipped with expanded and often novel receptors and adaptors. Novel Toll-like receptor (TLR) and MyD88-like genes lacking essential domains were highly up-regulated in the oyster, possibly interfering with TLR signal transduction. RIG-1/MDA5 receptors for viral RNA, interferon-regulatory factors, tissue necrosis factors and interleukin-17 were highly activated and likely central to the oyster{\textquoteright}s antiviral response. Genes related to anti-apoptosis, oxidation, RNA and protein destruction were also highly up-regulated, while genes related to anti-oxidation were down-regulated. The oxidative burst induced by the up-regulation of oxidases and severe down-regulation of anti-oxidant genes may be important for the destruction of viral components, but may also exacerbate oyster mortality. This study provides unprecedented insights into antiviral response in a mollusc. The mobilization and complex regulation of expanded innate immune-gene families highlights the oyster genome{\textquoteright}s adaptation to a virus-rich marine environment.

}, issn = {1095-9947}, doi = {10.1016/j.fsi.2015.05.023}, author = {He, Yan and Jouaux, Aude and Ford, Susan E and Christophe Lelong and Pascal Sourdaine and Mathieu, Michel and Guo, Ximing} }