Transcriptome of Crassostrea gigas infected by OsHV-1 at high temperatures

Among all the environmental factors, seawater temperature plays a decisive role in triggering marine diseases. Like fever in vertebrates, high seawater temperature modulates the host response to the pathogens in ectothermic animals. In France, massive mortality of Pacific oysters Crassostrea gigas caused by the ostreid herpes virus 1 (OsHV-1) is markedly reduced when temperatures exceed 24°C in the field. Here we assess how high temperature influences the host response to the pathogen by comparing transcriptomes (RNA-sequencing) during the course of experimental infection at 21°C (reference) and 29°C. We show that high temperature modified host physiological processes that are unfavorable to the viral infection. Temperature influenced the expression of transcripts related to immune process, increased the abundance of transcripts related to apoptotic process, synaptic signaling, and protein processes. Concomitantly, the abundance of transcripts associated to catabolism, metabolites transport, macromolecules synthesis and cell growth remained low since the first stage of infection at 29°C. Moreover, viral entry into the host seemed limited at 29°C by changes in extracellular matrix composition and protein abundance. These results provide new insights into how environmental factors modulate the host-pathogen interactions.