Comparative Analysis of Toll-Like Receptor Transcript Expression in Skin, Muscle, and Heart Between Healthy and Diseased Empurau (Tor tambroides)

TLR family is one of the most essential pattern-recognition receptors expressed in the innate immunity of fishes as they are involved in the defense mechanism against invading microbial pathogens. Following the first draft genome assembly of the Malaysian Mahseer (Tor tambroides), 14 TLR genes had been discovered and matched to the genome of T. tambroides. However, there is still a gap in knowledge on the roles of TLRs in T. tambroides in the event of a pathogenic infection. This study aimed to detect and observe the gene expression of TLRs in the skin, muscle, and heart tissue between healthy and diseased T. tambroides. In this study, RNA was isolated from healthy and Pesudomonas Fluorescenes-injected T. tambroides and the expression of TLRs were detected through semi-quantitative RT-PCR analysis. Prior to conducting semi-quantitative analysis, the TLR transcriptome were screened and analysed through BLASTn (NCBI) and MEME software whereby TLR gene variants were selected and four conserved motifs were identified. These conserved domains which consist of TIR, LRR, Internalin_A SF, and PPP1R42 SF were then used to design specific primers for tlr1b, tlr3b, tlr5b, tlr5c, tlr7e, and tlr9d. Gene expression for tlr1b, tlr3b, and tlr5b, in the skin, muscle and heart of healthy and diseased fish showed a correlation towards the immune response in a bacterial infection. In contrast, tlr7e, and tlr9d, did not express any significant gene expression levels in the event of a pathogenic incursion. Future studies will make use of molecular and proteomic tools both to study important elements in immune defence and prophylactic measures to assist with breeding programmes for disease resistance