Short communication Ontogeny and tissue-specific expression of innate immune related genes in rohu, Labeo rohita (Hamilton) S.P. Nayak, B.R. Mohanty, J. Mishra, P.R. Rauta, A. Das, A.E. Eknath, P.K. Sahoo * Central Institute of Freshwater Aquaculture, Kausalyaganga, Bhubaneswar 751 002, India article info Article history: Received 16 December 2010 Received in revised form 15 February 2011 Accepted 20 February 2011 Available online xxx Keywords: Labeo rohita Carp Innate immunity Ontogeny abstract The innate immune response in fish represents an early and rapid defense against pathogens. The present study aims at looking into ontogeny of innate immune system in the teleost, Labeo rohita using RT-PCR based approach. Total RNA extracted from unfertilized and fertilized eggs, and hatchlings (hatched at 28  2  C) at 0, 1, 3, 6, 12, 24 h, and 3, 7, 16, 21, 31 days post-fertilization were subjected to RT-PCR using self-designed or earlier published primers to amplify some innate immune relevant genes (lysozyme C, lysozyme G, beta-2 microglobulin, toll-like receptor 22-like and transferrin). The constitutive expression of b-actin was detected in unfertilized eggs and further developmental stages. Transferrin and TLR22-like mRNA transcripts were detected by RT-PCR from 6 h post-fertilization to 31 day post-fertil- ization, whereas b-2 microglobulin transcripts were detected only from 7 day post-fertilization onwards. Lysozyme C mRNA transcripts were detected from 24 h post-fertilization to 31 day post-fertilization. Lysozyme G mRNA transcripts were detected early from unfertilized egg stage onwards. Similarly, tissues viz. intestine, heart, ovary, gill, spleen, muscle, liver, brain, skin, anterior kidney, posterior kidney, and blood collected from juveniles of rohu were subjected to detection of all above mentioned gene tran- scripts by RT-PCR. b2-microglobulin mRNA transcript was expressed in all tissues. Lysozyme C mRNA expression is confined to blood and posterior kidney only whereas lysozyme G mRNA is expressed in all tissues. TLR22-like mRNA is expressed in all tissues except ovary and liver whereas transferrin mRNA transcript is detected only in liver. Finally, all these information taken are likely to shed light on the ontogeny of innate immunity in L. rohita, which offers new insights to developmental biology when compared to higher vertebrates and also helpful in the development of preventive measures against problems concerning infectious diseases. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The innate immune system is the only defense weapon of invertebrates and a fundamental defense mechanism of fish. The innate immune system, a phylogenetically older one being found in all multi-cellular organisms, also plays an instructive role in the acquired immune response and homeostasis, and is therefore equally important in higher vertebrates [1,2]. On the other hand, the adaptive system appeared about 450 million years ago and is found in all vertebrates, except jawless fish [1]. Ontogenesis is a sequence of molecular and cellular events regulated by time and space, leading to the development of a fully functional organism. The adaptive immune system in carp, however, starts developing from 3 dpf as indicated from rag-1 expression [3] and reaches functionality between 1 and 2 months [4]. The recombination activating genes (rag), Rag-1/Rag-2 expres- sion in carp indicated life-long new formation of putative T cells but reduced formation of B cells in older fish [3]. The innate immune system of all multi-cellular organisms is served by a variety of germline-encoded pattern recognition receptors (PRR) or pattern recognition proteins (PRP) [5]. The PRR can be soluble components like the complement protein C3, lectins and various other humoral innate components or they can be expressed as receptors on phagocytes and other cells of the immune system. TLR-associated signal-transduction pathways have been identified as critical components of innate immunity, found in all invertebrates and vertebrate species examined to-date. TLRs and cytokines have also been shown to be expressed during early stages of teleost devel- opment [6]. One of TLRs detected in fish, TLR22, but absent in mammals in functional form, is interesting because it’s activity has been up-regulated with respect to gram negative bacteria or viral (simulated with poly I:C) infections [6e8]. Transferrin is an acute * Corresponding author. Fax: þ91 674 2465407. E-mail address: pksahoo1@hotmail.com (P.K. Sahoo). Contents lists available at ScienceDirect Fish & Shellfish Immunology journal homepage: www.elsevier.com/locate/fsi 1050-4648/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.fsi.2011.02.014 Fish & Shellfish Immunology xxx (2011) 1e5 Please cite this article in press as: Nayak SP, et al., Ontogeny and tissue-specific expression of innate immune related genes in rohu, Labeo rohita (Hamilton), Fish & Shellfish Immunology (2011), doi:10.1016/j.fsi.2011.02.014