Gene Expression During Scale Development in Pachyrhynchus Weevils

The diverse and colorful patterns found in organisms serve various functions. In Pachyrhynchus weevils, these colors and patterns composed of 3D photonic architectures function as signals for sexual selection and aposematism. Previous study of photonic structure suggests the involvement of specific genes in color regulation in Pachyrhynchus weevils. However, the genes responsible for scale coloring in Pachyrhynchus weevils have remained unknown. In this study, RNA-seq was conducted in P. nobilis at 6 h and 24 h after emergence, comparing elytra (no-scale) and scale tissues during the period of coloring. qPCR validation was performed across three species (P. nobilis, P. sarcitis, and P. orbifer). RNA-seq analysis identified 3172 and 2890 DEGs at 6 h and 24 h after emergence, respectively, with up-regulated DEGs increasing over time. The candidate genes were selected based on functional annotations related to scale development (C-type lectins, cuticle proteins, and Yellow family proteins), and KEGG pathway analysis. qPCR validation revealed species-specific expression patterns: C-type lectin-encoding gene was expressed in P. nobilis and P. sarcitis but absent in P. orbifer, while Hedgehog-like protein-encoding gene was exclusively detected in P. orbifer. Temporal analysis showed significant differences in Wnt signaling pathway between developmental stages in P. orbifer, and marginal significance in calcium signaling pathway gene in P. sarcitis. This study suggests that these specific genes may play roles in color regulation during scale development in Pachyrhynchus weevils, with varying expression at different time points after emergence or among species.