Characterization of Spectrin Family Genes and Their Evolutionary Roles in Domestication and Breeding of the Silkworm Bombyx mori

The spectrin family genes play critical roles in cytoskeletal organization and cellular integrity, yet their evolutionary and functional significance in non-classical model organisms remains poorly explored. Here, we systematically identified and characterized spectrin family genes in the silkworm <i>Bombyx mori</i>. Genome-wide analysis identified 17 predicted spectrin genes, which were integrated into eight optimized members through transcriptome-guided structural refinement. Multi-species genomic analysis revealed 8, 23, and 24 spectrin family genes in <i>Drosophila melanogaster</i>, <i>Mus musculus</i>, and <i>Homo sapiens</i>, respectively. Phylogenetic analysis revealed conserved clades across insects and mammals, with gene family expansions in vertebrates. Spatiotemporal expression profiling demonstrated ubiquitous expression of these genes during silkworm development. Population genomic analyses detected strong selection signatures in <i>BmTrio</i> during domestication and implicated <i>BmBeta_spc</i> as a candidate gene for silk yield enhancement in Chinese-improved strains (CHN-I). Expression profiles of parental strains and F₁ offspring from a commercial hybrid cross (Jingsong × Haoyue) revealed <i>BmBeta_spc</i> expression correlating with heterosis in silk yield traits. This study elucidates the characterization and functional relevance of silkworm spectrin genes, providing insights into their roles in domestication and breeding.