Sequence characteristics and expression profiles of Pax-5 and Blimp-1 in Epinephelus coioides following parasite infection and bacterial vaccination

In mammals, the transcription factors paired box-5 (Pax-5) and B-lymphocyte-induced maturation protein-1 (Blimp-1) maintain strict command of B-cell differentiation from hematopoietic stem cells to plasma cells. Here, we identified the Pax-5 and Blimp-1 genes and their predicted proteins in the orange-spotted grouper (Epinephelus coioides). Grouper Pax-5 was predicted to contain a paired box domain and a positive regulator domain, and five zinc fingers were predicted in grouper Blimp-1. Sequence alignment revealed that grouper Pax-5 and Blimp-1 shared a high sequence identity with that of other teleosts, particularly in the functional motifs. Tissue distribution analysis demonstrated that all tissues studied from healthy grouper expressed Pax-5 and Blimp-1. Pax-5 had the highest expression in vital lymphoid tissues (p < 0.05), whereas Blimp-1 expression was relatively equal among tissues (p> 0.05). In view of the conserved functions of Pax-5 and Blimp-1, we studied the progression of B cell differentiation in mucosal and systematic immunity by detecting the expression of these genes after infection with the parasite Cryptocaryon irritans and following vaccination with Vibrio harveyi. The expression level of grouper Blimp-1, IgM and IgT were significantly upregulated (p < 0.05), and the response occurred earlier in the systemic immune than the mucosal immune.