Limited early transcriptome-wide mucosal response to the bacterial pathogen Yersinia ruckeri in Atlantic salmon (Salmo salar) alevins
Fish mucosal surfaces form a complex immunological barrier that serves as the first line of defence against pathogens. While immune responses at these surfaces are well-characterised in juvenile and adult fish, our understanding of these processes during early developmental stages remains limited. Current knowledge suggests that fish larvae have a restricted ability to mount an immune response to bacterial pathogens, despite the presence of immune structures, effector cells, and molecules. This study examines the transcriptome-wide landscape of the early immune response to Yersinia ruckeri, the causative agent of Enteric Redmouth Disease, in Atlantic salmon (Salmo salar) alevins. Larvae were exposed to the pathogen for two hours, and samples were collected at 2, 6, 24, 48, and 72 hours post-exposure for RNA-Seq analysis. The study focused on three mucosal organs, namely, skin, gills, and tongue to understand how these surfaces, which are in direct contact with the pathogen, orchestrate immune responses in the hours following exposure.