Contents lists available at ScienceDirect Fish and Shellfish Immunology journal homepage: www.elsevier.com/locate/fsi Full length article Gene profiling of antimicrobial peptides, complement factors and MHC molecules from the skin transcriptome of Channa striatus and its expression pattern during Aeromonas hydrophila infection Venkatesh Kumaresan a , Mukesh Pasupuleti b , Bilal Ahmad Paray c , Mohammad K. Al-Sadoon c , Jesu Arockiaraj d,* a Department of Biotechnology, Faculty of Science and Humanities, SRM Institute of Science and Technology, Kattankulathur, 603 203, Chennai, Tamil Nadu, India b Lab PCN 206, Microbiology Division, CSIR-Central Drug Research Institute, B.S. 10/1, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, 226 031, Uttar Pradesh, India c Department of Zoology, College of Science, King Saud University, PO Box 2455, Riyadh, 11451, Saudi Arabia d SRM Research Institute, SRM Institute of Science and Technology, Kattankulathur, 603 203, Chennai, Tamil Nadu, India ARTICLE INFO Keywords: Channa striatus Skin transcriptome Aeromonas hydrophila Complement components Adaptive immunity Antimicrobial peptide ABSTRACT Channa striatus is one of the economically important freshwater fish with high demand in Southeast Asia for its nutritional and medicinal values. The unique composition of skin mucus of murrel provides immunity against pathogens; however, they are susceptible to few bacterial pathogens especially Aeromonas hydrophila. Although few immune molecules such as antimicrobial peptides have already been identified from the murrel mucus, there is no report on the complete gene profile of the skin and mucosal immunity. Therefore, in this study we applied transcriptome approach to identify the mRNA sequences of various immune molecules such as antimicrobial peptides, complement factors and adaptive immune molecules from the skin tissue. Transcriptome wide search revealed unique mRNA sequences of 13 antimicrobial peptides, 11 complement components, 2 major histo- compatibility complex proteins and its receptor, 6 butyrophilins, 2 leptins and its receptor. Brief bioinformatics analysis of the identified mRNA sequences and their respective putative protein sequences were performed to understand molecular information of those immune components. Further, we analysed the differential expres- sion pattern of selected 13 mRNA sequences representing each immune group using qRT-PCR technique which highlighted the role of those genes during A. hydrophila challenge. Overall, this study revealed the complex immune response of murrel skin and the involvement of various innate and adaptive immune molecules against A. hydrophila infection. 1. Introduction Channa striatus is a tropical, air breathing carnivorous fish which is commonly found in freshwater bodies of Asian countries especially India, Sri Lanka, China, Indonesia, Philippines, Vietnam and Thailand. In India, it is one of the most economically important species for its tasty flesh with nutritive and medicinal properties. The fish is con- sumed mainly to recover the lost energy after prolonged illness and to elevate wound healing process after surgeries. Reports suggested that murrel has a wide range of medicinal properties such as wound healing, antimicrobial property, antinociceptive property, osteoarthritic treat- ment, antioxidant property, cardiological treatment and neurological property [1]. Although epizootic ulcerative syndrome (EUS) is one of the common diseases found in C. striatus, they are also infected with various bacteria, fungi, virus and parasites. So far, various reports stated that murrel was susceptible to bacterial pathogens such as Aeromonas hydrophila, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella salmoni- cida [2]. However, the murrel skin protects the fish from those patho- gens where the mucus plays a key role in protection. Murrel mucus has unique composition of immune molecules which highly contributes to the protective mechanisms of fish against pathogens [3,4]. Also, we have identified and reported various cytokines, antioxidant molecules, pattern recognition receptor (PRR) molecules such as lectins and few proteases, caspases and heat shock proteins from C. striatus and their differential expression pattern during A. hydrophila infection [5–7]. Rauta et al. [8] analysed the immunoglobulin (Ig) response in the serum of C. striatus to formalin-killed A. hydrophila antigen and implicated the https://doi.org/10.1016/j.fsi.2018.09.061 Received 6 July 2018; Received in revised form 19 September 2018; Accepted 23 September 2018 * Corresponding author. E-mail address: jesuarockiaraj.a@ktr.srmuniv.ac.in (J. Arockiaraj). Fish and Shellfish Immunology 84 (2019) 48–55 Available online 24 September 2018 1050-4648/ © 2018 Elsevier Ltd. All rights reserved. T