Genome-Wide Identification and Evolution of Core Cell Cycle Genes in Marchantia polymorpha: Insights Into Redundancy, Stress, and Functional Evolution.

The cell cycle is a fundamental process of plant growth, development, and reproduction, in which cyclin-dependent kinases (CDKs) and cyclins (CYCs) play central roles in regulating the progression through various stages. These proteins are coordinated with multiple interacting partners to ensure the accurate execution of essential biological events such as DNA replication, chromosome segregation, and cell division. Marchantia polymorpha, one of the earliest diverging land plant species, has emerged as a key model for exploring fundamental mechanisms in plant biology and evolution. However, compared with other model plants, such as Arabidopsis thaliana and Oryza sativa, the core cell cycle genes in M. polymorpha remain relatively uncharacterized. In this study, we identified 31 core cell cycle genes in M. polymorpha through genome-wide analysis, including 13 CDKs, 8 CYCs, 5 E2F/DPs, 1 ICK, 1 RB, 1 CKS, and 2 Wee1 genes. We further analyzed their physicochemical properties, gene structures, and conserved domains, along with evolutionary pressures assessed via Ka/Ks and 4DTv analyses. Comparative genomic analysis revealed patterns of gene contraction and expansion. Additionally, we predicted cis-acting regulatory elements and performed differential expression analysis under various stress conditions to explore their potential functions and expression profiles. Finally, a protein-protein interaction (PPI) network was constructed, and key genes were experimentally validated. These findings provide valuable insights into the core cell cycle gene family in M. polymorpha, contributing to an enhanced understanding of cell cycle regulation and its evolutionary significance in plants.