Résumé
Of all environmental factors, seawater temperature plays a decisive role
in triggering marine diseases. Like fever in vertebrates, high seawater
temperature could modulate the host response to pathogens in ectothermic
animals. In France, massive mortality of Pacific oysters, Crassostrea
gigas, caused by the ostreid herpesvirus 1 (OsHV-1) is markedly reduced
when temperatures exceed 24°C in the field. In the present study 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 induced host physiological processes that are unfavorable to
the viral infection. Temperature influenced the expression of transcripts
related to the immune process and increased the transcription of genes
related to the apoptotic process, synaptic signaling and protein processes
at 29°C. Concomitantly, the expression of genes associated with
catabolism, metabolite transport, macromolecule synthesis and cell growth
remained low from the first stage of infection at 29°C. Moreover, viral
entry into the host might have been limited at 29°C by changes in
extracellular matrix composition and protein abundance. Overall, these
results provide new insights into how environmental factors modulate
host–pathogen interactions.