Venom trade-off shapes interspecific interactions, physiology, and reproduction

Isolation and identification of toxins inhibiting Shal potassium channels from the venom of Ornithoctonus hainana spider

The spider, Ornithoctonus hainana, is a large and formidable predatory arthropod that possesses strong lethality towards rodents through its venoms. Its venom and constituent bioactive peptide toxins have previously been shown to modulate the activity of voltage-gated ion channels. Therefore, venom toxins are an important weapon for rapidly subduing prey or escaping predators. Here, we discovered three new peptide toxins, termed HNTXs, from the venom of O. hainana. These toxins potently inhibit the peak currents of rKv4.2, a member of the Shal channel family. We demonstrated that HNTXs are gating modifiers that shift the voltage dependence of activation and inactivation to more positive potentials. Additionally, chimeric channel and site-directed mutagenesis analyses show that these toxins inhibit rKv4.2 by interacting with the S3-S4 linker in the channel. Furthermore, we found that HNTXs exhibited different responses to Shal channels of vertebrates and invertebrates, suggesting that venomous animals employ diversified toxins to efficiently and accurately defend against predation and interspecific competition. This research may expand our understanding of venom peptides in evolutionary adaptation.

A comparative analysis of toxin gene families across diverse sea anemone species

All species from order Actiniaria (sea anemones) are venomous, even though most are of no threat to humans. Currently, we know very little about the toxin gene complement of highly venomous members of this order. To address this gap in knowledge, we sequenced the transcriptome of the highly venomous and medically significant Hell's Fire sea anemone, Actinodendron plumosum, as well as five distantly related species, Cryptodendrum adhaesivum, Epiactis australiensis, Heteractis aurora, Isactinia olivacea and Stichodactyla mertensii. We used bioinformatic approaches to identify their toxin gene complements and performed a comparative evolutionary analysis of seven understudied toxin families. Of the 16 toxin families identified, 12-40 candidate toxins were found in the six new sea anemone transcriptomes, with only 12 candidates in eight toxin families identified in A. plumosum. Across 26 sea anemone species, six neurotoxin families showed evidence of taxonomic restriction, whereas the phospholipase A2 toxin family was ubiquitously distributed. Additionally, we identified two alternative forms for the phospholipase A2 toxin family, a 10- and 14-cysteine framework, which warrant further structural and functional characterisation. Overall, we have identified a comprehensive list of toxins from a wide diversity of sea anemone species that provides the basis for future research to structurally and functionally characterise novel candidates for potential use as therapeutics or for agricultural applications.

Venoms of Lepidoptera: Evolution, Composition, and Molecular Modes of Action

Animal venoms are a focus of research due to the hazards they represent and to their relationship to evolution and ecology, pharmacology, biodiscovery, and biotechnology. Venoms have evolved multiple times in Lepidoptera, mostly as defensive adaptations that protect the larval life stages. While venoms are always produced in structures derived from cuticle and setae, they are diverse in their composition and bioactivity, reflecting their multiple evolutionary origins. The most common result of envenomation by lepidopterans is pain and inflammation, but envenomation by some species causes fatal hemorrhagic syndromes or chronic inflammatory conditions in humans or veterinary pathologies such as equine amnionitis and fetal loss. The handful of lepidopteran venom toxins that have been characterized includes coagulotoxins from Lonomia obliqua (Saturniidae) and pain-causing cecropin-like peptides from Doratifera vulnerans (Limacodidae). However, our knowledge of lepidopteran venoms remains comparatively poor, with further studies required to yield a clear picture of the evolution, composition, and function of venoms produced by Lepidoptera.

Sea Anemone Membrane Attack Complex/Perforin Superfamily Demonstrates an Evolutionary Transitional State between Venomous and Developmental Functions

Gene duplication is a major force driving evolutionary innovation. A classic example is generating new animal toxins via duplication of physiological protein-encoding genes and recruitment into venom. While this process drives the innovation of many animal venoms, reverse recruitment of toxins into nonvenomous cells remains unresolved. Using comparative genomics, we find members of the Membrane Attack Complex and Perforin Family (MAC) have been recruited into venom-injecting cells (cnidocytes), in soft and stony corals and sea anemones, suggesting that the ancestral MAC was a cnidocyte expressed toxin. Further investigation into the model sea anemone Nematostella vectensis reveals that three members have undergone Nematostella-specific duplications leading to their reverse recruitment into endomesodermal cells. Furthermore, simultaneous knockdown of all three endomesodermally expressed MACs leads to mis-development, supporting that these paralogs have nonvenomous function. By resolving the evolutionary history and function of MACs in Nematostella, we provide the first proof for reverse recruitment from venom to organismal development.