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Disease outbreaks caused by iridoviruses are known to affect farmed flounder (Paralichthys olivaceus) and turbot (Scophthalmus maximus). To facilitate quantitative real time RT-PCR (qRT-PCR) analysis of gene expression in flounder and turbot during viral infection, we in this study examined the potentials of 9 housekeeping genes of flounder and turbot as internal references for qRT-PCR under conditions of experimental infection with megalocytivirus, a member of the Iridoviridae family. The mRNA levels of the 9 housekeeping genes in the brain, gill, heart, intestine, kidney, liver, muscle, and spleen of flounder and turbot were determined by qRT-PCR at 24h and 72h post-viral infection, and the expression stabilities of the genes were determined with geNorm and NormFinder algorithms. The results showed that (i) viral infection induced significant changes in the mRNA levels of the all the examined genes in a manner that was dependent on both tissue type and infection stage; (ii) for a given time point of infection, stability predictions made by the two algorisms were highly consistent for most tissues; (iii) the optimum reference genes differed at different infection time points at least in some tissues; (iv) at both examined time points, no common reference genes were identified across all tissue types. These results indicate that when studying gene expression in flounder and turbot in relation to viral infection, different internal references may have to be used not only for different tissues but also for different infection stages., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Half-smooth tongue sole (Cynoglossus semilaevis) is an important economic fish species cultured in northern China. In this study, we identified and analyzed the expression and function of a megalocytivirus-induced gene, CsMig1, from tongue sole. The deduced amino acid sequence of CsMig1 is composed of 507 residues and contains no conserved domains. Blast analysis identified no close homologues of CsMig1. CsMig1 shares moderate sequence similarities in the N-terminal region with the Gig1 (i.e., grass carp hemorrhagic virus-induced gene) homologues of several teleost species. Quantitative real time RT-PCR analysis showed that constitutive CsMig1 expression occurred, in increasing order, in heart, spleen, muscle, kidney, liver, gill, and gut. Experimental infection with the viral pathogen megalocytivirus upregulated CsMig1 expression in kidney, spleen, and liver in time-dependent manners. Treatment of head kidney lymphocytes with the culture supernatant of megalocytivirus-stimulated cells significantly enhanced CsMig1 expression. When head kidney lymphocytes were transfected with the plasmid that constitutively expresses CsMig1, the cells exhibited significantly increased ability to resist megalocytivirus infection. Taken together, these results indicate that CsMig1 is a virus- and, possibly, interferon-induced novel immune factor that functions in the antiviral immunity of tongue sole., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The IκB kinase β (IKKβ) plays crucial roles in regulating activation of nuclear factor-kappa B (NF-κB) in response to proinflammatory factors and microbial and viral infections. Here, we report the cloning of an IKKβ cDNA (named SicIKKβ) from the mandarin fish Siniperca chuatsi. The full-length cDNA is 4052bp and contains an ORF that encodes a predicted protein of 743-amino acid residues. The deduced amino acid sequence of SicIKKβ has the same domain organization as human IKKβ, which consists of a serine/threonine kinase domain, a leucine zipper motif and a putative helix-loop-helix motif. Quantitative RT-PCR showed that SicIKKβ was ubiquitously expressed in tissues of mandarin fish, and its expression in mandarin fish fry (MFF-1) cells was up-regulated during the course of ISKNV infection., (2010 Elsevier B.V. All rights reserved.)

C1q, a subunit of the C1 complex, plays a key role in the recognition of immune complexes to initiate the classical complement pathway. In this study, we reported two C1q-like cDNAs from mandarin fish (Siniperca chuatsi), mC1q-like-1 (mC1qL1) and mC1q-like-2 (mC1qL2). The full-length cDNA of mC1qL1was 990bp, containing a 71bp 5'-untranslated region (UTR), an open reading frame (ORF) of 723bp, and a 196bp long 3'-UTR. mC1qL2 cDNA was 1193bp, containing a 100bp 5'-UTR, followed by an ORF of 756bp and a 3'-UTR of 337bp. mC1qL1 and mC1qL2 share 29% identity in amino acid sequence. Both mC1qL1 and mC1qL2 contained three parts: a short amino-terminal region, a collagen-like region and a carboxyl-terminal globular C1q domain. The phylogenetic analysis showed that mC1qL1 clustered with two Danio rerio hypothetical proteins and further grouped with C1q proteins, while mC1qL2 clustered with C1qA proteins from other species. In healthy mandarin fish, mC1qL1 and mC1qL2 were expressed in all tissues tested, including liver, spleen, head kidney, caudal kidney, intestine and gill. mC1qL1 was highly expressed in head kidney, while mC1qL2 was mainly expressed in spleen. The expression level of mC1qL1 and mC1qL2 in liver were not changed obviously and mC1qL2 was significantly changed (p<0.05) in spleen after infectious spleen and kidney necrosis virus (ISKNV) infection. Mandarin fish C1q may play a role in response to ISKNV infection.