Wnt6 and Wnt10 regulate spot marking formation in Bombyx mori larvae.

Insect pigmentation patterns are critical for ecological adaptation and serve as an excellent model for studying the genetic basis of phenotypic diversity. The Wnt family is a conserved group of genes that play crucial roles in various biological processes across species. While Wnt1 and WntA have been extensively characterized for their roles in insect coloration, particularly in Drosophila and butterflies, the functions of other Wnt family members, such as Wnt6 and Wnt10, remain poorly understood. These genes originated from a common ancestor with Wnt1 and are arranged in tandem with it in the genome. In this study, we investigated the roles of Wnt6 and Wnt10 in spot formation in silkworm larvae using 3 spot-marking mutants with similar phenotypes. Through gene expression analysis, RNA interference, and overexpression studies, we discovered that Wnt1, Wnt6, and Wnt10 each regulate spot formation via the Armadillo-dependent canonical Wnt pathway. This highlights their distinct and nonredundant functional attributes despite their common origin and genomic arrangement. Additionally, we identified a uridine diphosphate glycosyltransferase (UDP-glycosyltransferase) gene contributes to caterpillar pigmentation related to the canonical Wnt pathway. Our findings underscore the complexity and conservation of the Wnt signaling pathway in insect coloration.