Newly Identified Toxin Transcripts in Myanmar Russell’s Viper Venom Gland

Abstract

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 had not been sequenced until recently. Hence, RNA sequencing has been used to predict genes that encode this snake’s toxins. This can lead to deeper insights into the pathogenesis of envenoming and potential drug discovery. Venom glands were dissected from four adult D. siamensis specimens (two males and two females) provided by a local Myanmar snake farm. The 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 using RSEM software. The 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, 28 full-length sequences represented the eight newly identified toxin gene families in D. siamensis, including neprilysin (2), cystatin (5), 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 resembled typical elapid toxins, which usually exhibit neurotoxic activities and tissue damage. A smaller proportion of candidate toxin transcripts were predicted to display antimicrobial activity and anti-metastatic effects. Our results suggest their functional activities. They should be studied further for potential therapeutic applications.

Keywords

• Russell’s viper
• venom gland
• toxin transcript