Peçonha de Dinoponera quadriceps como fonte de substâncias bioativas : uma abordagem transcriptomica e peptidomica

Abstract

Dinoponera quadriceps is a predatory giant ant that inhabits the tropical regions and subdues its prey (insects) with stings that deliver a toxic cocktail of molecules. Human accidents occasionally occur and cause local inflammation, pain and systemic symptoms. A comprehensive study of the D. quadriceps venom gland transcriptome is required to advance our knowledge about the toxin repertoire of the giant ant venom to evaluate the presence of substances with biotechnological value and to understand the physiopathological basis of Hymenoptera envenomation. We conducted a transcriptome analysis of a cDNA library from the D. quadriceps venom gland with Sanger sequencing in combination with whole-transcriptome shotgun deep sequencing. From the cDNA library using Sanger methodology, a total of 420 independent clones were analyzed resulting in 21 contigs and 39 singlets. Although the proportion of dinoponeratoxin isoform precursors was high, the first giant ant venom inhibitor cysteine-knot (ICK) toxin was found. The deep next generation sequencing yielded a total of 2.514.767 raw reads that were assembled into 18.546 contigs. A Blast search of the assembled contigs against non-redundant and Swiss-Prot databases showed that 73,27% of transcripts from NGS and 71% from Sanger corresponded to hits and indicated an interesting diversity of transcripts related to venom gene expression. The majority of these venom-related sequences code for a major polypeptide core, which comprises venom allergens, lethal-like proteins and esterases, and a minor peptide framework composed of inter-specific structurally conserved cysteine-rich toxins. Both cDNA library and deep sequencing yielded large proportions of contigs that showed no similarities with known sequences or were classified as hypotethical proteins.To improve the investigation, we performed a proteomic analysis with the crude venom of D. quadriceps. It was possible to confirm the presence of mature toxins evidenced through the transcriptome and predict the precursors processing and post-translational modifications. To our knowledge, this is the first report of the venom gland transcriptome of the New World giant ant D. quadriceps. The glandular venom system was dissected, and the toxin arsenal was revealed; this process brought to light novel sequences that included an ICK-folded toxins, allergen proteins, esterases. These findings contribute to the understanding the venom constituints the ecology, behavior and venomics of hymenopterans.