~ 116 ~ International Journal of Fisheries and Aquatic Studies 2020; 8(4): 116-123 E-ISSN: 2347-5129 P-ISSN: 2394-0506 (ICV-Poland) Impact Value: 5.62 (GIF) Impact Factor: 0.549 IJFAS 2020; 8(4): 116-123 © 2020 IJFAS www.fisheriesjournal.com Received: 16-05-2020 Accepted: 20-06-2020 Esha Arshad 1. Marine Biotechnology Division, Indian Council of Agricultural Research - Central Marine Fisheries Research Institute, Ernakulam North, Kochi, Kerala, India 2. Faculty of Marine Sciences, Lakeside Campus, Cochin University of Science and Technology, Kochi, Kerala, India MA Pradeep Marine Biotechnology Division, Indian Council of Agricultural Research - Central Marine Fisheries Research Institute, Ernakulam North, Kochi, Kerala, India CS Subin Marine Biotechnology Division, Indian Council of Agricultural Research - Central Marine Fisheries Research Institute, Ernakulam North, Kochi, Kerala, India KK Vijayan Indian Council of Agricultural Research - Central Institute of Brackishwater Aquaculture, Chennai, Tamil Nadu, India Corresponding Author: Esha Arshad 1. Marine Biotechnology Division, Indian Council of Agricultural Research - Central Marine Fisheries Research Institute, Ernakulam North, Kochi, Kerala, India 2. Faculty of Marine Sciences, Lakeside Campus, Cochin University of Science and Technology, Kochi, Kerala, India Differential gene expression analysis implicates wild Magallana bilineata (Röding, 1798) to be in an enhanced immunological status than laboratory- maintained oysters Esha Arshad, MA Pradeep, CS Subin and KK Vijayan Abstract Oysters are filter-feeding bivalves thriving in estuaries and inter-tidal zones. As sessile invertebrates, oysters have evolved a well-developed stress tolerance mechanism to tolerate various environmental stressors such as altered hydrological parameters, microbial pathogens, and anthropogenic influences. The focus of this study was to identify the key genes which enable the Indian oyster (Magallana bilineata) to overcome the turbulent conditions in their environment. Suppression subtractive hybridization (SSH) technique was used to generate the differentially expressed genes in wild Magallana bilineata in comparison to laboratory-maintained ones. The method revealed twenty functionally relevant genes with roles in immunity, stress, cellular processes, cytoskeleton, and lipid metabolism. The diverse set of genes obtained from the SSH library are known to have direct and indirect roles in oyster immunity, suggesting that the wild oysters are more immune stimulated and active than laboratory- maintained ones. The expression of ten potentially upregulated genes was analysed using quantitative real-time PCR. Keywords: Magallana bilineata, SSH, stress, immunity, real-time PCR 1. Introduction The marine environment constitutes the most mercurial of all habitats owing to its seasonal climatic fluctuations and increasingly, due to anthropogenic threats. These changes vastly influence the aquatic ecosystems, especially, coastal and estuarine habitats and cause significant physiological stress on the animals [1, 2] . These animals in such a challenging environment may flourish or perish, depending on its capability to acclimatize to natural variations and anthropogenic factors [3] . Learning the mechanisms by which marine organisms attune to the local disturbances is pivotal to gain a better perspective of their physiological tolerance limits as well as the plasticity of the ecosystem. Molluscs such as oysters are key ecosystem engineers and play vital roles in the effective functioning of marine, freshwater and terrestrial ecosystems [4] . They are model organisms to study the effect of climatic change on marine ecosystems. Oysters, in their natural environment, are exposed to a range of environmental stressors which they withstand to thrive. Stressors like altered abiotic hydrological parameters including temperature, salinity, and pH occur regularly in their habitat [5, 6] . The oysters are vulnerable to a motley of microbes in their waters which they accumulate due to their filter feeding nature and are also periodically exposed to air during daily and seasonal cycles [7] . In addition to all this, several anthropogenic factors like water and sediment pollution can have adverse effects on the animal. Increased pollution also increases the susceptibility of the oyster to aquatic epizootics [8] . The resilient nature of these immobile animals can be attributed to their phenotypic plasticity and modification of gene expression to maintain cellular homeostasis [9] . Cues regarding the complex mechanisms by which the oysters get its sturdiness have been opened up by the recent whole-genome sequencing of the Pacific oyster. Researchers were able to confirm the role and interplay of a multitude of genes that assist in environmental adaptation [10, 4] . With the help of various genomic tools, it is possible to identify the specific set of genes which can regulate the essential physiological processes required for the animals to cope with the changing environment.