Identification of Novel Toxin Genes from the Stinging Nettle Caterpillar Parasa lepida (Cramer, 1799): Insights into the Evolution of Lepidoptera Toxins

Abstract

Many animal species can produce venom for defense, predation, and competition. The venom usually contains diverse peptide and protein toxins, including neurotoxins, proteolytic enzymes, protease inhibitors, and allergens. Some drugs for cancer, neurological disorders, and analgesics were developed based on animal toxin structures and functions. Several caterpillar species possess venoms that cause varying effects on humans both locally and systemically. However, toxins from only a few species have been investigated, limiting the full understanding of the Lepidoptera toxin diversity and evolution. We used the RNA-seq technique to identify toxin genes from the stinging nettle caterpillar, Parasa lepida (Cramer, 1799). We constructed a transcriptome from caterpillar urticating hairs and reported 34,968 unique transcripts. Using our toxin gene annotation pipeline, we identified 168 candidate toxin genes, including protease inhibitors, proteolytic enzymes, and allergens. The 21 P. lepida novel Knottin-like peptides, which do not show sequence similarity to any known peptide, have predicted 3D structures similar to tarantula, scorpion, and cone snail neurotoxins. We highlighted the importance of convergent evolution in the Lepidoptera toxin evolution and the possible mechanisms. This study opens a new path to understanding the hidden diversity of Lepidoptera toxins, which could be a fruitful source for developing new drugs.

Diversity of the Antimicrobial Peptide Genes in Collembola

“…Previously, Alo peptides present in Hemiptera and Coleoptera were proposed to evolve via horizontal gene transfer from plants or fungi based on the idea that its knottin domain is unique to plants and fungi [ 20 ]. However, recent studies show that proteins containing knottin domain play essential roles in many animal toxins, including nettle caterpillars, spiders, scorpions, and cone snails [ 73 ]. Thus, the evolution of arthropod Alo peptides may also be explained by multiple gene gains and loss events.…”

De Novo Transcriptome Assembly for Venom Gland in Two Spe-Cies of Spiders (Sinopoda Pengi and Trichonephila Clavata)

“…To remove potentially nontoxic orthologs, all candidate toxin unigenes were used as queries for the local BLASTX search (e-value = 1e-5) against two databases: (1) animal-reviewed proteins in the UniprotKB and (2) toxin protein database, as explained previously. Unigenes were ltered out from the candidate toxin gene dataset if the BLAST score of the best hit from the animal protein database was higher than the animal toxin database results [14].…”