To identify the component(s) involved incellcycle control in the protozoanGiardialamblia, cells arrested at the G1/S- orG2-phaseby treatment with nocodazole and aphidicolin were prepared from the synchronizedcellcultures.RNA-sequencinganalysis of the 2 stages ofGiardiacellcycle identified severalcellcyclegenesthat were up-regulated at theG2-phase. Transcriptome analysis of cells in 2 distinctcellcycle stages of G.lambliaconfirmed previously reported components ofcellcycle (PcnA, cyclin B, and CDK) and identified additionalcellcycle components (NEKs, Mad2, spindle pole protein, and CDC14A). This result indicates that thecellcycle machinery operates in this protozoan, one of the earliest diverging eukaryotic lineages.