Molecular Cloning and Expression Analysis of Xbp1-S of Nile Tilapia (Oreochromis niloticus)

Abstract:

X-box binding protein 1-S (Xbp1-S) is a key transcript factor mainly associated with B cell development and differentiation. The 1380 bp full-length cDNA of OnXbp1-S including 1155 bp ORF, 127 bp 5'UTR and 98 bp 3'UTR was cloned with RACE, which encodes 384 amino acids with a molecular weight of 41.32 kDa and a theoretical isoelectric point of 4.36. Homology analysis revealed that the OnXbp1-S gene was homologous to other fish with the most similarity with Notothenia coriiceps. OnXbp1-S expresses in all tested tissues, with the highest mRNA expression in liver, and the highest protein level in thymus and the lowest protein level in muscle. Streptococcus agalactiae stimulation induced the expression of OnXbp1-S with the highest level at 192 h post-infection. In addition, mature B cells have a much higher OnXbp1-S level than naive B cells. Taken together, the results indicated that OnXbp1-S might be involved in the immune response in Nile tilapia against S. agalactiae infection, and play a role in B cell development and differentiation.