<i>Bombyx mori Cdc25</i> is involved in regulating the G2/M phase of the silkworm cell cycle

Endoreplication plays a crucial role in the morphogenesis of various organs. The silk gland of Bombyx mori, which produces silk after maturation, engages in a unique cell cycle transition, mitosis-to-endoreplication, in the early stages of formation. This plays an essential role in the secretion of silk protein from silk gland cells. In this study, we identified and analyzed the expression characteristics of BmCdc25. The functional domain of BmCdc25 is conserved across species. BmCdc25 is mainly expressed in the G2/M phase of the cell cycle, and is expressed at low levels in the silk gland during active endoreplication. Overexpression of BmCdc25 enhanced cell proliferation, while inhibition of BmCdc25 caused cells to accumulate in the G2/M phase, thereby inhibiting cell proliferation. Additionally, BmCdc25 overexpression prevented DNA replication during silk gland cell endoreplication, while BmCdc25 inhibition had the opposite effect. BmZFP67 was confirmed to regulate BmCdc25 transcription by chromatin immunoprecipitation and electrophoretic mobility shift assays, while aberrant cytokinesis caused by knockout of BmZFP67 was shown to involve BmCdc25. Our findings expand the regulatory network of BmZFP67 from the perspective of transcriptional regulation and protein interaction and provide insight into the roles of BmCdc25 in the silkworm cell cycle.