Newly identified toxin transcripts in Myanmar Russell’s viper venom gland

Russell’s viper (Daboia siamensis) is a medically important snake in Myanmar due to its high morbidity and mortality. The genome of Myanmar Russell’s viper has not sequenced until recently, thus RNA-Sequencing has been used to predict genes encoding this snake’s toxins. Venom glands were dissected from four adult D. siamensis specimens (two males and two females) provided by a local Myanmar Snake Farm. mRNA was extracted and sequenced on the Illumina HiSeq platform, then assembled de novo using the Trinity software. Candidate toxin genes were identified using the Venomix pipeline and their expression levels were calculated by mean of RSEM software. Identified toxin candidates were aligned with previously described venom proteins using Clustal Omega. Candidate venom transcripts were classified into 23 toxin gene families, which included 53 unique transcripts identified as full-length sequences. Among them, 39 full-length sequences represented the nine newly identified toxin gene families in D. siamensis: Neprilysin (2), Cystatin (5), Latrotoxins (11), Waprin (1), Vipericidin (1), Veficolin (1), Endothelial lipases (9), Vespryn (ohanin) (8) and three finger toxins (1). Their expression levels were found to be moderate to low (TPM= 1.49 to 213.37). The majority of the toxin candidates were resembled to typical toxins found in elapids, with a majority of the toxins exhibiting neurotoxic activity and tissue damage. A smaller proportion of candidate toxin transcripts were predicted to exhibit antimicrobial activity and anti-metastatic effect. Our results indicate their functional activities could be studied further for therapeutic applications.