Cell cycle control across the eukaryotic kingdom

• Most eukaryotic diversity in cell cycle control is unexplored.
• Key cell cycle regulators have undergone divergent functional specifications.
• Early eukaryotes already had complex cell cycle regulation.
• Eukaryotic cell cycle regulation appears to be a highly dynamic and adaptive process.
• Human cell cycle regulators share more similarities with control factors from plants than with those from yeast.

Almost two billion years of evolution have generated a vast and amazing variety of eukaryotic life with approximately 8.7 million extant species. Growth and reproduction of all of these organisms depend on faithful duplication and distribution of their chromosomes to the newly forming daughter cells in a process called the cell cycle. However, most of what is known today about cell cycle control comes from a few model species that belong to the unikonts; that is, to only one of five ‘supergroups’ that comprise the eukaryotic kingdom. Recently, analyzing species from distantly related clades is providing insights into general principles of cell cycle regulation and shedding light on its evolution. Here, referring to animal and fungal as opposed to non-unikont systems, especially flowering plants from the archaeplastid supergroup, we compare the conservation of central cell cycle regulator functions, the structure of network topologies, and the evolutionary dynamics of substrates of core cell cycle kinases.