Molecular characterization and expression of ZAP-70 in Nile tilapia (Oreochromis niloticus) in response to Streptococcus agalactiae stimulus

The 70 kDa zeta-chain associated protein kinase (ZAP-70) plays a critical role in effective signal transductions that are fundamental to T cell differentiation, proliferation and effector functions. In this paper, the ZAP-70 gene of Nile tilapia, Oreochromis niloticus (designated as On-ZAP-70) was cloned and its expression pattern under the stimulation of Streptococcus agalactiae was investigated. Sequence analysis showed important structural characteristics required for TCRs signal transduction were detected in the deduced amino acid sequence of On-ZAP-70, and the deduced genomic structure of On-ZAP-70 was similar to the known ZAP-70. In healthy tilapia, the On-ZAP-70 transcripts were mainly detected in the thymus, spleen, head kidney and gill. Moreover, there was a clear time-dependent expression pattern of On-ZAP-70 after immunization and the expression reached the highest level at 48 h in the spleen and head kidney, and at 72 h in the thymus, respectively. This is the first report on the expression of ZAP-70 induced by intracellular bacteria vaccination in teleosts. These findings indicated that On-ZAP-70 may play an important role in the immune response to intracellular bacteria in Nile tilapia.