Transcriptome And Expression Profiling Analysis Of Spleen And Structure And Function Of Peroxiredoxin 4 From Large Yellow Croaker

In recent years, with the rapid development of the large yellow croaker(Pseudosciaena crocea)culture industry, the infectious diseases caused by viruses, bacteria, and parasites are becoming more and more severe, resulting in great economic losses. However, little has been known about the molecular mechanisms of the immune response to such pathogenic viruses and bacterias in this fish species, thereby hindering the establishment of effective measures in disease control.We constructed a Solexa cDNA library from the spleen of fish infected with poly (I:C). In total, 15,192 unigenes were identified in this transcriptome. Novel high-throughput deep sequencing technology was also used to investigate the transcriptome of large yellow croaker infected with A.hydrophila. This computational analysis identified 8,216 genes. Furthermore, a comparative analysis of the expression profile in fish infected with A. hydrophila or untreated was conducted. This analysis produced 1,996 differentially expressed genes of which 1,133 and 863 were upregulated and downregulated, respectively, in response to bacterial infection. The Gene Ontology and GENMAPP databases were used to classify these genes. Dramatic differences were observed in genes involved in inflammatory responses, suggesting that this process plays an important role in the early stages of infection. A. hydrophila infection affected the gene expression of many components of signaling cascades, including the Toll-like receptor, JAK-STAT, and MAPK pathways. Interestingly, genes encoding factors involved in T cell receptor (TCR) signaling were also revealed to be down regulated by infection in these fish, suggesting that TCR signaling was suppressed at this early period. These results revealed changes of multiple signaling pathways involved in immunity during A. hydrophila infection, which will facilitate our comprehensive understanding of the mechanisms involved in the immune response to bacterial infection in large yellow croaker.The peroxiredoxin 4 (Prx4) from the large yellow croaker is a typical 2-Cys Prx with an N-terminal signal peptide. Here, we describe the crystal structure of this antioxidant at 1.90 ?. This structure revealed an extra N-terminal antiparallelβ-sheet that contributes to the dimer interface. Deletion of thisβ-sheet significantly decreased the in vitro peroxidase activity of Prx4. In vivo assays further demonstrated that thisβ-sheet was also critical for the functions of Prx4 to negatively regulate nuclear factor-?B (NF-?B) activity and to perform its role in anti-bacterial immunity. Moreover, these results will help us to further understand the immune responses and disease-resistance mechanism in large yellow croaker.