Transcriptome Analysis Of Liver From Large Yellow Croaker (Pseudosciaena Crocea) During Cryptocaryon Irritans Infection And Cloning And Expression Of Three Histones

Large yellow croaker(Pseudosciaena crocea Richardson,1846), one of major mariculture species in China, has the largest output among marine fish of cage culture. However, along with the development of intensive culture and the pollution of aquaculture environment, many pathogens have emerged, particularly marine cryptocaryonosis (white spot disease). The white spot disease have caused substantial economic damage in the large yellow croak farming industry.At present, little is known about P. crocea-Cryptocaryon irritans interaction. Therefore, to better understand the host-pathogen interactions in large yellow croaker, we investigated the liver transcriptome response of large yellow croaker toward C. irritans infection. We constructed a transcriptome library from the liver of large yellow croaker before and after infected C. irritans using high-throughput sequencing. In total,51360 isogenes were identified in this transcriptome. Furthermore, a comparative analysis of the expression profile in large yellow croaker infected with C. irritans and untreated group was conducted. This analysis produced 3841 differentially expressed isogenes of which 2129 were upregulated and 1712 were downregulated, in response to the parasite infection. The Gene Ontology data bases were used to classify the isogenes. The parasite infection affected the gene expression of Toll-like receptor signaling pathways. TLR signaling may involved in immunity response during the early C. irritans infection, leading to the production of proinflammatory cytokines. Several core acute phase proteins (C-type lectin, hepcidin, apolipoprotein) expression levels were elevated, which indicate that C. irritans infection induces acute phase response in P. crocea. These results emphasize the importance of teleost innate immune responses against an ectoparasitic infection.Nowadays, the treatment methods controlling marine cryptocaryonosis rely on the traditional physical and chemical methods. These methods have limited effects and cause serious problems such as drug residues and water pollution. So there is a strong need for effective and environmentally friendly treatment drugs in the mariculture industry. Antimicrobial peptides (AMPs) play a crucial role in the nonspecific (innate) immunity system of fish. They have potent broad-spectrum antibacterial, antifungal, antiviral and antiparasitic activities. AMPs have been identified as effective replacements for antibiotics. In recent years, it is reported that histone or histone-derived peptides have potent activity against fish pathogens and little hemolysis activity. In this study, we cloned histone H1, H2A, H2B gene from large yellow croaker. The complete mRNA of histone H1 was 1388 bp encoding a protein of 195 amino acids (aa). This protein had theoretical molecular weight of 20793.2 Da and theoretical pI of 10.99, riched in lysine, alanine and proline. The protein was predicted to be heat resistant, stable and hydrophilic. The complete mRNA of histone H2A was 905 bp encoding a protein of 128 amino acids (aa). This protein had theoretical molecular weight of 13731.1 Da and theoretical pI of 10.88, riched in lysine, alanine, glycine and arginine. The protein was predicted to be heat resistant and hydrophilic. The complete mRNA of histone H2B was 860 bp encoding a protein of 126 amino acids (aa). This protein had theoretical molecular weight of 13934.1 Da and theoretical pI of 10.31, riched in lysine, alanine and serine. The protein was predicted to be heat resistant, stable and hydrophilic. Compared to other fish histones, we indicated that histone H1, H2A, H2B of large yellow croaker and their derived peptides may have potent activity against bacteria, fungi, virus and parasites. The quantitative data revealed histone H1 was highly expressed in gill, liver, intestine, brain and muscle among the examined tissues. Histone H2B was highly expressed in gill and brain. Histone H2B was highly expressed in muscle. The expression of histone H1, H2A and H2B were significantly regulated during C. irritans infection and secondary bacterial infections. The results indicated that the three histones might involve in the immune defense system against C. irritans infections.