Deep sequencing analysis of toad Rhinella schneideri skin glands and partial biochemical characterization of its cutaneous secretion

• Published in: Journal of Venomous Animals and Toxins including Tropical Diseases
• Main Authors: Priscila Yumi Tanaka Shibao, Camila Takeno Cologna, Romualdo Morandi-Filho, Gisele Adriano Wiezel, Patricia Tiemi Fujimura, Carlos Ueira-Vieira, Eliane Candiani Arantes
• Format: Article in Journal/Newspaper
• Language: English
• Published: SciELO 2018
• Subjects: RNA-seq; Rhinella schneideri; Toad secretion; Transcriptome; Illumina; Cutaneous secretion; Arctic medicine. Tropical medicine; RC955-962; Toxicology. Poisons; RA1190-1270; Zoology; QL1-991; Arctic
• Online Access: https://doi.org/10.1186/s40409-018-0173-8; https://doaj.org/article/66d4c9e3485740318457ac03d2366a44

Abstract Background Animal poisons and venoms are sources of biomolecules naturally selected. Rhinella schneideri toads are widespread in the whole Brazilian territory and they have poison glands and mucous gland. Recently, protein from toads’ secretion has gaining attention. Frog skin is widely known to present great number of host defense peptides and we hypothesize toads present them as well. In this study, we used a RNA-seq analysis from R. schneideri skin and biochemical tests with the gland secretion to unravel its protein molecules. Methods Total RNA from the toad skin was extracted using TRizol reagent, sequenced in duplicate using Illumina Hiseq2500 in paired end analysis. The raw reads were trimmed and de novo assembled using Trinity. The resulting sequences were submitted to functional annotation against non-redundant NCBI database and Database of Anuran Defense Peptide. Furthermore, we performed caseinolytic activity test to assess the presence of serine and metalloproteases in skin secretion and it was fractionated by fast liquid protein chromatography using a reverse-phase column. The fractions were partially sequenced by Edman’s degradation. Results We were able to identify several classes of antimicrobial peptides, such as buforins, peroniins and brevinins, as well as PLA2, lectins and galectins, combining protein sequencing and RNA-seq analysis for the first time. In addition, we could isolate a PLA2 from the skin secretion and infer the presence of serine proteases in cutaneous secretion. Conclusions We identified novel toxins and proteins from R. schneideri mucous glands. Besides, this is a pioneer study that presented the in depth characterization of protein molecules richness from this toad secretion. The results obtained herein showed evidence of novel AMP and enzymes that need to be further explored.