Characterization of TmDnmt1: From In Silico Prediction to Developmental, Tissue‐Specific, and Infection‐Responsive Expression in Tenebrio molitor

Abstract

DNA methylation is a fundamental epigenetic modification that governs genome stability, transcriptional regulation, and development across diverse eukaryotes. While DNA methyltransferases (Dnmts) are well‐characterized in vertebrates, coleopteran insects exhibit a unique evolutionary architecture characterized by the exclusive retention of Dnmt1, prompting the need to investigate its potential role in epigenetic regulation. In this study, we identified and comprehensively characterized the maintenance DNA methyltransferase gene from Tenebrio molitor, designated as TmDnmt1. In silico domain and phylogenetic analyses confirmed that TmDnmt1 retains the evolutionarily conserved architectural domains characteristic of canonical Dnmt1 proteins and clusters closely with coleopteran orthologs. Developmental expression profiling revealed a pronounced upregulation during the late larval and early pupal stages, alongside robust embryonic expression, pointing to its potential role during metamorphosis and tissue remodeling. Tissue‐specific analysis demonstrated widespread transcription with particularly high expression in immune‐active and barrier tissues, such as hemocytes and the gut. Furthermore, time‐course expression analysis following systemic challenge with Escherichia coli, Staphylococcus aureus, and Candida albicans showed rapid, pathogen‐ and tissue‐dependent transcriptional induction, especially a rapid upregulation in hemocytes at 3 h post‐injection. These findings raise the possibility that TmDnmt1 acts as a rapid epigenetic regulator involved in coordinating immediate innate immune responses. Taken together, this study establishes a foundational baseline for understanding the intersection of epigenetics, development, and innate immunity in coleopteran insects.