Inhibitor of REL/NF-КB is regulated in Sydney rock oysters in response to specific double-stranded RNA and Vibrio alginolyticus, but the major immune anti-oxidants EcSOD and Prx6 are non-inducible

Invertebrates, such as oysters have mechanisms to recognize different microbial associated molecular patterns (MAMPs) and recognition of these antigens triggers signaling pathways for the transcription of immune-related proteins. Components of the Rel/NF-КB pathway have been identified in mollusks but the role of different MAMPs in the activation of this pathway is poorly understood. In the current study, the Sydney rock oyster (Saccostrea glomerata) was injected intramuscularly with a range of different MAMPs. Oysters were sampled over a 24 h period and the difference in expression of genes associated with immunity was determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) using RNA extracted from hemocytes. The results showed that oysters can discriminate between different nucleic acids and double-stranded RNA sequences for activation of the Rel/NF-КB pathway in S. glomerata. Polyinosinic–polycytidylic acid (poly I:C) up-regulated expression of inhibitor of Rel/NF-КB (IКB) by 26-fold and interferon-inhibiting cytokine (IK) by 2.2-fold, whereas polycytidylic acid–polyguanylic acid (poly G:C) and double stranded Vibrio alginolyticus genomic DNA (dsDNA) did not. IКB was also up-regulated 3.8-fold higher for oysters stimulated with V. alginolyticus bacterial cells suggesting that lipopolysaccharide (LPS) also activates the Rel/NF-КB pathway. The expressions of extracellular superoxide dismutase (EcSOD) and peroxiredoxin 6 (Prx6) were not significantly affected by dsRNA, dsDNA or V. alginolyticus bacterial cells suggesting that these two genes, previously demonstrated to be important in the resistance of S. glomerata to disease are not directly inducible by these MAMPs. This is the first study investigating differences in expression kinetics of immune genes in response to challenge from different MAMPs in this economically important bivalve species.