Mutation in Resilin reveals attachment impairment in Bombyx mori.

Insects can effortlessly walk on various substrate surfaces using attachment pads on their feet, even upside down on smooth surfaces. These pads undergo frequent deformation throughout the lifecycle of insects to achieve stable adhesion. Interest in insect adhesion spans 100s of years; studies have indicated the special mechanical properties and intricate structural design of insect attachment pads. However, the genetic basis of their function remains unclear. Resilin, an elastic protein widely distributed in insect exoskeletons, plays a crucial role in many physiological activities. Here, we identified a resilin-like protein in the Lepidopteran insect Bombyx mori and generated mutants for this gene. The resulting adults exhibited "slipping" phenotype and reduced attachment ability. Further behavioral investigations, microscopic observations and mechanical performance tests, confirmed that the mutation stiffened the attachment pads, reducing flexibility and effective contact area, which ultimately led to decreased adhesive ability in adults. Molecular-level analyses revealed that the resilin-like mutation led to differential expression of melanin metabolism-related genes, potentially explaining the hardening and abnormal pigmentation of the attachment pads. Our results provide genetic and phenotypic evidence demonstrating the significant role of resilin in insect attachment.