Venom Proteins of the Firefly Pyrocoelia analis Revealed by Transcriptome Analysis

Fireflies, which predominantly prey on various mollusks such as small snails and slugs, are renowned for their unique bioluminescence. Firefly toxins-particularly Lucibufagins (LBGs), which target the α-subunit of the sodium-potassium pump protein (ATPα)-play a crucial role in their survival strategies. However, the types and functions of venom proteins in fireflies remain to be elucidated. In this study, transcriptome sequencing was employed on the larval head of Pyrocoelia analis larvae, through which transcripts encoding several putative venom proteins were identified, including phospholipase A1/A2, 5'-nucleotidase, cysteine-rich secretory proteins (CRISPs), and insulin-like peptides. Structural comparison revealed that venom proteins in fireflies exhibited high sequence and structural similarity with venom proteins from various venomous animals (e.g., snakes, scorpions, spiders, and cone snails). These venom proteins may exert synergistic effects through multiple mechanisms, such as neurotoxicity, metabolic interference, and cytotoxicity, thereby playing an essential role in mollusk predation and defense against predators. Our study not only analyzes the complexity and uniqueness of Py. analis venom proteins but also provides a robust foundation for further exploration of the ecological adaptability and evolutionary mechanisms of these venom proteins.