Journal of Fish Biology (2016) 88, 1949–1964 doi:10.1111/jfb.12960, available online at wileyonlinelibrary.com Identifcation and expression analysis of the sting gene, a sensor of viral DNA, in common carp Cyprinus carpio X. L. Cao*†, J. J. Chen‡, Y. Cao‡, G. X. Nie† and J. G. Su*§ *College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, People’s Republic of China, †College of Fisheries, Henan Normal University, Xinxiang, 453007, People’s Republic of Chinaand ‡College of Life Science, Henan Normal University, Xinxiang, 453007, People’s Republic of China (Received 28 March 2015, Accepted 19 February 2016) Stimulator of interferon gene (sting) was identifed and characterized from common carp Cyprinus carpio. The sting messenger (m)RNA encoded a polypeptide of 402 amino acids with a calculated molecular mass of 46·184 kDa and an isoelectronic point of 6·08. The deduced protein of sting con- tained a signal peptide, three transmembrane motifs in the N-terminal region and four putative motifs (RXR) found in resident endoplasmic reticulum proteins. mRNA expression of sting was present in twelve investigated tissues, and was up-regulated by koi herpesvirus (KHV) in vivo and in vitro. The transcription of sting was altered by poly(I:C) and poly(dT:dA) stimulation in vitro. The fndings sug- gested that sting is an inducible gene involved in innate immunity against DNA- and RNA-derived pathogens. To investigate defence mechanisms in C. carpio development, sting level in embryos, lar- vae and juvenile fsh was monitored following KHV challenge. The sting message was negligible in embryos prior to hatching, but observed at higher transcriptional levels throughout larval and juvenile stages. Investigation showed the mRNA expression profles of genes encoding for proteins promoting various functions in the interferon pathway, from pattern recognition receptors to antiviral genes, to be signifcantly induced in all examined organs by in vivo infection with KHV. Following KHV infection, the ifn message was signifcantly downregulated in spleen, head kidney, brain and hepatopancreas but notably up-regulated in gill, intestine and skin, suggesting that ifn induction might be related to the mucosal immune system and virus anti-ifn mechanisms. These results provided the basis for further research into the role and mechanisms of sting in fshes. © 2016 The Fisheries Society of the British Isles Key words: gene cloning; koi herpesvirus; mRNA expression; sting. INTRODUCTION Koi herpesvirus (KHV), also known as cyprinid herpesvirus 3 (CyHV-3), is consid- ered among the most dangerous of fsh pathogens. KHV infection in common carp Cyprinus carpio L. 1758 and its ornamental koi varieties, causes KHV disease, a severe systemic disease that is a serious threat to C. carpio aquaculture (Hanson et al., 2011; Rakus et al., 2013). KHV disease is characterized by rapid viral replication and spread to multiple organs, resulting in mortality (Rakus et al., 2009; Piaˇ cková et al., 2013). A better understanding of the defence of C. carpio against this virus §Author to whom correspondence should be addressed. Tel.: +86 29 8709 2139; email: sujianguo2015@163.com 1949 © 2016 The Fisheries Society of the British Isles