Abstract
Biological responses of zebra mussel Dreissena polymorpha are investigated to assess the impact of contaminants on aquatic organisms and ecosystems. In addition to concentrate chemical contaminants in their tissues, zebra mussels accumulate several microorganisms such as viruses, protozoa and bacteria. In order to understand the molecular mechanisms involved in the defence against microorganisms this study aims at identifying immune proteins from D. polymorpha hemolymph involved in defence against protozoa and viruses. For this purpose, hemolymph were exposed ex vivo to Cryptosporidium parvum and RNA poly I:C. Differential proteomics on both hemocytes and plasma revealed immune proteins modulated under exposures. Different patterns of response were observed after C. parvum and RNA poly I:C exposures. The number of modulated proteins per hemolymphatic compartments suggest that C. parvum is managed in cells while RNA poly I:C is managed in plasma after 4 h exposure. BLAST annotation and GO terms enrichment analysis revealed further characteristics of immune mechanisms. Results showed that many proteins involved in the recognition and destruction of microorganisms were modulated in both exposure conditions, while proteins related to phagocytosis and apoptosis were exclusively modulated by C. parvum. This differential proteomic analysis highlights in zebra mussels modulated proteins involved in the response to microorganisms, which reflect a broad range of immune mechanisms such as recognition, internalization and destruction of microorganisms. This study paves the way for the identification of new markers of immune processes that can be used to assess the impact of both chemical and biological contaminations on the health status of aquatic organisms.
Highlights
Biological responses of zebra mussel Dreissena polymorpha are investigated to assess the impact of contaminants on aquatic organisms and ecosystems
A differential proteomic analysis was conducted on hemocytes and plasma from the hemolymph challenged with immune modulators in order to identified proteins involved in the immune defence of D. polymorpha
The comparative proteomic analysis performed on hemocytes and plasma exposed to C. parvum and RNA polycytidylic acid (poly I):C has provided a large set of information on the immune processes involved in anti-protozoal and anti-viral defence of D. polymorpha
Summary
Biological responses of zebra mussel Dreissena polymorpha are investigated to assess the impact of contaminants on aquatic organisms and ecosystems. Interaction between the immune system of bivalves and microorganisms have been mainly investigated in marine bivalves due to their economic interests and the high number of infectious diseases affecting aquaculture farms[7] These studies resulted in the identification of several cellular and molecular immune mechanisms involved in the defence against important pathogens. Considering the high number of immune proteins observed in plasma, the need to consider both intracellular and extracellular fractions to investigate the immune defence occurring in the hemolymph compartments was pointed out This proteogenomic analysis was performed on zebra mussels that were physiologically acclimated to laboratory conditions and only gave a cartography of potential immune-related proteins without exploring their interactions with microbes. A comparative proteomic analysis was performed on both hemocytes and plasma fractions to reveal immune-related proteins modulated by C. parvum and RNA polyinosinic-polycytidylic acid (poly I:C) exposures
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