Cloning, Exogenous Expression and Function Analysis of Interferon-γ from Gadus macrocephalus.

Interferon γ (IFN-γ) is now considered to be one of the key molecules in the regulation of innate and adaptive immunity. The function of IFN-γ is best described in humans, but less of IFN-γ in fish species has been described at protein level. In the present study, IFN-γ from Gadus macrocephalus (GmIFN-γ) has been examined in terms of bioinformatics, prokaryotic expression, yeast expression, antiviral activity and immune regulatory function. The cDNA of GmIFN-γ contains an open reading frame of 570 nucleotides, coding 189 amino acids. The mature protein contains a nuclear localization signal motif and an obvious IFN-γ signature sequence at the C-terminal. GmIFN-γ is very similar to that of Atlantic cod, with homology up to 89.89%, but less than 32% to other species. GmIFN-γ can be detected in the gills, spleen, intestine, brain and kidney. Interestingly, during early development, a strong signal of GmIFN-γ was not detected until 40 days post hatching. Prokaryotic expression plasmid pET-32a-GmIFN-γ was constructed, and the expression products in BL21 were confirmed by Mass Spectrometry. Meanwhile, the plasmid pGAPZA-GmIFN-γ with Myc tag was constructed and transmitted into Pichia pastoris yeast GS115, and the products were tested using Western blot. The purified GmIFN-γ from either BL21 or yeast has a strong antivirus (Spring viremia of carp virus) effect. The vector of pcDNA3.1-GmIFN-γ was expressed in EPC cell lines; high transcript levels of MHC class I chain-related protein A (MICA) gene were detected; and the exogenous GmIFN-γ protein could also induce MICA expression, indicating that GmIFN-γ could stimulate immune response. The yeast GS115 with GmIFN-γ protein, which is an inclusion body, was given to zebrafish orally, and the transcript of zebrafish IFN-γ was upregulated significantly; however, genes of the interferon type-I signal pathway were not well stimulated.

Differential gene expression profile of the calanoid copepod, Pseudodiaptomus annandalei, in response to nickel exposure.

To better understand the underlying mechanisms of reactions of copepods exposed to elevated level of nickel, the suppression subtractive hybridization (SSH) was used to elucidate the response of the copepod Pseudodiaptomus annandalei to nickel exposure at the gene level. P. annandale is one of a few copepod species that can be cultured relatively easy under laboratory condition, and it is considered to be a potential model species for toxicity study. In the present study, P. annandalei were exposed to nickel at a concentration of 8.86 mgL(-1) for 24h, after which the RNA was prepared for SSH using unexposed P. annandalei as drivers. A total of 474 clones on the middle scale in the SSH library were sequenced. Among these genes, 129 potential functional genes were recognized based on the BLAST searches in NCBI and Uniprot databases. These genes were then categorized into nine groups in association with different biological processes using AmiGO against the Gene Ontology database. Of the 129 genes, 127 translatable DNA sequences were predicted to be proteins, and the putative amino acid sequences were searched for conserved domains (CD) and proteins using the CD-Search service and BLASTp. Among 129 genes, 119 (92.2%) were annotated to be involved in different biological processes, while 10 genes (7.8%) were classified as an unknown-function gene group. To further confirm the up-regulation of differentially expressed genes, the quantitative real time PCR were performed to test eight randomly selected genes, in which five of them, i.e. α-tubulin, ribosomal protein L13, ferritin, separase and Myohemerythrin-1, exhibited clear up-regulation after nickel exposure. In addition, MnSOD was further studied for the differential expression pattern after nickel exposure and the results showed that MnSOD had a time- and dose-dependent expression pattern in the copepod after nickel exposure. To the best of our knowledge, this is the first attempt to investigate the toxicity effects of nickel on a copepod at molecular level.