A newly evolved small secretory peptide enhances mechanical properties of spider silk

Spiders' ability to spin foraging webs using silk from specialized glands represents a remarkable evolutionary innovation, yet the molecular evolution of silk glands remains unclear. Here, we investigated the evolution of silk glands in Araneoidea spiders through genomic and transcriptomic mining. After the divergence of the Araneoidea clade, numerous new genes with simplified structures and constrained expression emerged, expressed predominantly in silk glands and coexpressed with ancient genes to drive the evolution of silk glands. Among these, SpiCE-DS8, a newly evolved small secretory peptide unique to the Nephilinae subfamily, interacted with the N-terminal of MaSp1b and was incorporated into dragline silk, potentially aiding in silk solidification. In vitro wet-spinning experiments demonstrated that SpiCE-DS8 enhanced fiber properties, likely enabling spiders to arm their foraging webs for more efficient prey capture. These findings highlight the pivotal role of lineage-specific genes in silk gland evolution and provide insights for synthetic silk development.