Evolutionary Patterns of the Genes Involved in the Integrity and Segregation of Chromosomes in Sawflies (Hymenoptera:...

The genes involved in the regulation of the meiotic process act important roles in maintaining the structural integrity of chromosomes, ensuring accurate mitotic segregation, and preserving genome stability. Although the structural and functional components of the cohesin and condensin complexes have been extensively investigated in model organisms, their evolutionary diversification and conservation levels in insects remain largely unknown. Here, we characterized and comparatively analyzed the architectural and functional features of the genes encoding these complexes in the more primitive and largely phytophagous suborder Symphyta (Hymenoptera: Insecta). The genome and transcriptome datasets representing 11 sawfly families and six superfamilies of sawflies were analyzed to identify the genes. These analyses identified 10 and 12 genes, as well as a total of 46 conserved motifs. The physicochemical properties and amino acid composition of these proteins are consistent with nucleoplasmic functions, acting main roles in DNA binding and protein-protein interactions. The result of phylogenetic analyses provides evidence for the hypothesis that the SMC genes originated from an ancient duplication of a single ancestral SMC gene. The absence of the CAPG2 gene in certain species, coupled with the occurrence of species-specific duplication events in most of the genes, indicates substantial heterogeneity in the evolutionary dynamics of these complexes. Despite the strong purifying selection pressure acting on the genes, positive selection signals were predicted in certain positions of the CAPG2, RAD21, and SA genes. These findings suggest that these genes exhibit conserved and species-specific evolutionary features in this insect lineage, consistent with their central roles in chromosome organization and cell cycle regulation.