| Mannose receptor(MR) is a member of pattern-recognition receptors(PRRs) which plays a significant role in immunity responses. Much work on MR has been done in mammals and birds while little in fish. In this report, Aeromonas sobria,(designated as ZA) which caused diseases of Zebrafish(Danio rerio) has been isolated and identified, zebra fish-A.sobria infection model have been established. The results were as follows:1. In this report, a MR gene(designated as zfMR) was cloned from zebra fish. The full-length cDNA of zfMR contains 6248 bp, consisted of a 5’terminal untranslated region(UTR) of 119 bp, a 3’UTR of 1842 bp, and an open reading frame(ORF) of 4287 bp encoding a polypeptide of 1428 amino acids. The predicted amino acid sequences showed that zfMR contained a cysteine-rich domain, a single FN II domain, eight CTLDs, a transmembrane domain and a short C-terminal cytoplasmic domain, sharing highly conserved structures with MRs from the other species. The phylogenetic tree showed that MRs from zebra fish, grass carp and blunt snout bream were clustered in teleost clade.2. In zebra fish, the mRNA transcripts of MR were found to be constitutively expressed in a wide range of tissues with different levels, including liver, spleen, kidney, intestine, gill, brain, heart, muscle and skin, with highest level in kidney.3. Temporal expression patterns of MR, IL-1β and TNF-α mRNAs were analyzed in the liver, spleen, kidney and intestine of zebra fish post of the infection with A.sobria. By immunohistochemistry assay, slight enhancement of MR protein was also observed in the spleen and intestine of the infected zebra fish, indicating its involvement in innate immune regulation during bacterial infections.The relationship between the expression of inflammatory cytokines and the involvement of zfMR needs to be elucidated, the established zebra fish-A.sobria infection model will be valuable for elucidating the role of MR in fish immune responses to infection. |
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