Lineage-Specific Venom Gene Expression Shapes Chemical Diversity in Cephalopods

Area of Science:

• Evolutionary biology
• Biochemistry
• Zoology

Background:

• Animal venoms are rich in novel compounds, but their evolutionary origins and diversification are poorly understood, especially in cephalopods.
• Cephalopod venom systems, used for predation, defense, and competition, have largely unexplored genetic architectures, secretory cells, and glands.
• Only one cephalopod venom compound, SE-CTX, with known sequence and paralytic activity, has been described.

Purpose of the Study:

• To reconstruct the evolutionary history, molecular diversity, and glandular localization of SE-CTX-like proteins in cephalopods.
• To identify and characterize novel venom gene families in decapodiform cephalopods (squids and cuttlefish).
• To understand the origin, diversification, and integration of venom genes within cephalopod venom arsenals.

Main Methods:

• Multimodal approach including phylogenetic analysis, protein structure prediction, and comparative genomics.
• Identification of homologs across 20 squid and cuttlefish species.
• Proteomic analysis, imaging, and histological examination of venom glands.

Main Results:

• Discovery of a new venom gene family, deca-ctx, specific to decapodiform cephalopods.
• Identification of 29 deca-ctx homologs, indicating a single origin followed by extensive gene duplication and diversification.
• Prediction of significant structural diversity within DECA-CTX proteins and confirmation of their expression and localization in venom glands.

Conclusions:

• SE-CTX is part of a diverse and evolutionarily ancient venom system in cephalopods, not an isolated protein.
• The deca-ctx gene family represents a significant expansion of our understanding of cephalopod venom evolution.
• Cephalopods provide a key model for studying the emergence, diversification, and functional integration of novel venom genes.