Cloning, characterization, and function of MyD88 in silvery pomfret (Pampus argenteus) in response to bacterial challenge

Myeloid differentiation factor 88 (MyD88) is a key and universal downstream adapter for most Toll-like receptors (TLRs) and plays an important role in both the innate and adaptive immune response. In this study, the full-length cDNA of MyD88 (PAMyD88) from silvery pomfret (Pampus argenteus) was cloned and characterized. The PAMyD88 cDNA is 1545 bp in length and contains an 876 bp open reading frames (ORF). Multiple sequence alignment and phylogenetic tree analyzes revealed that the amino acid sequence of PAMyd88 was homologous to a variety of previously MyD88 molecules characterized from other species. The quantitative real-time reverse transcription-PCR analysis showed that the PAMyD88 mRNA was broadly expressed in all examined tissues, with higher levels observed in the immune-relevant organs. The results showed a significant up-regulation of the TLR2 and PAMyD88 transcript levels in response to L. plantarum and C. butyricum and a substantial expression level of TLR4 and PAMyD88 induced by V. anguillarum. Additionally, a challenge with V. anguillarum resulted in significant apoptosis, whereas the L. plantarum and C. butyricum induced only low levels of apoptosis. These data provide insight into the roles of PAMyD88 in the TLR signaling pathway in response to probiotic and pathogenic bacteria in silvery pomfrets.