Venom toxin genes are tandem-arrayed beyond gene-family-size expectations in four venomous bilaterian species

Toxin genes in four venomous bilaterian species are tandem-arrayed beyond gene-family-size expectations, with clustering enrichment dropping from 14–31-fold to about 2–6-fold versus size-matched non-toxin families.

• Why it matters: It is unclear whether tandem-array architecture is toxin-specific or simply reflects how large gene families cluster, so the study tests toxin clustering against size-matched non-toxin families.
• What they did: Using five venomous genomes, including a new chromosome-level genome of Scolopendra mutilans with a 12-individual venom-gland proteome, the authors compared toxin versus non-toxin gene-family clustering across multiple family definitions and genomic window sizes.
• The result: The toxin excess persisted as matched odds ratios above 1 (2–6-fold enrichment; windows of 25–200 kb under the primary definition), mainly driven by homologous neighboring copies, while tandem toxin copies showed no detectable expression differences.

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