A novel murrel Channa striatus mitochondrial manganese superoxide dismutase: gene silencing, SOD activity, superoxide anion production and expression Jesu Arockiaraj • Rajesh Palanisamy • Prasanth Bhatt • Venkatesh Kumaresan • Annie J. Gnanam • Mukesh Pasupuleti • Marimuthu Kasi Received: 2 January 2014 / Accepted: 26 August 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract We have reported the molecular charac- terization including gene silencing, superoxide activ- ity, superoxide anion production, gene expression and molecular characterization of a mitochondrial manga- nese superoxide dismutase (mMnSOD) from striped murrel Channa striatus (named as CsmMnSOD). The CsmMnSOD polypeptide contains 225 amino acids with a molecular weight of 25 kDa and a theoretical isoelectric point of 8.3. In the N-terminal region, CsmMnSOD carries a mitochondrial targeting sequence and a superoxide dismutases (SOD) Fe domain (28–109), and in C-terminal region, it carries another SOD Fe domain (114–220). The CsmMnSOD protein sequence shared significant similarity with its homolog of MnSOD from rock bream Oplegnathus fasciatus (96 %). The phylogenetic analysis showed that the CsmMnSOD fell in the clade of fish mMnSOD group. The monomeric structure of CsmMnSOD possesses 9 a-helices (52.4 %), 3 b-sheets (8.8 %) and 38.8 % random coils. The highest gene expression was noticed in liver, and its expression was inducted with fungal (Aphanomyces invadans) and bacterial (Aeromonas hydrophila) infections. The gene silenc- ing results show that the fish that received dsRNA exhibited significant (P \ 0.05) changes in expression when compared to their non-injected and fish physi- ological saline-injected controls. The SOD activity shows that the activity increases with the spread of infection and decreases once the molecule controls the pathogen. The capacity of superoxide anion produc- tion was determined by calculating the granular blood cell count during infection in murrel. It shows that the infection influenced the superoxide radical production which plays a major role in killing the pathogens. Overall, this study indicated the defense potentiality of CsmMnSOD; however, further research is necessary to explore its capability at protein level. Keywords Channa striatus Á MnSOD Á Gene silencing Á SOD activity Á Superoxide production J. Arockiaraj (&) Á R. Palanisamy Á P. Bhatt Á V. Kumaresan Division of Fisheries Biotechnology and Molecular Biology, Department of Biotechnology, Faculty of Science and Humanities, SRM University, Kattankulathur, Chennai 603 203, Tamil Nadu, India e-mail: jesuaraj@hotmail.com A. J. Gnanam Institute for Cellular and Molecular Biology, The University of Texas at Austin, 1 University Station A4800, Austin, TX 78712, USA M. Pasupuleti Lab PCN 206, Microbiology Division, CSIR-Central Drug Research Institute, B.S. 10/1, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226031, Uttar Pradesh, India M. Kasi Department of Biotechnology, Faculty of Applied Sciences, AIMST University, Semeling Bedong, 08100 Bedong, Kedah, Malaysia 123 Fish Physiol Biochem DOI 10.1007/s10695-014-9981-0