The C. reinhardtii genome project has allowed the comprehensive analysis and expression profiling of its core cell cycle genes (Bisova et al. 2005). This work identified clear homologs of cyclins A, B, and D, CDKA, and the plant-specific CDKB. There are also a few highly divergent CDKs and cyclins that are specific to C. reinhardtii. In contrast to Ostreococcus tauri (see below), no clear homolog of Cdc25 phosphatase was identified. The expression profiling unraveled two different profiles among cell cycle genes: a constitutive profile that was seen for CDKA and CYCD; and a regulated profile with peaks of mRNA amounts at commitment point and cell division, typical for CDKB, CYCA, and CYCB. The overall organization of C. reinhardtii cell cycle genes was more plant-like and metazoan-like than are yeasts' cell cycle genes. Conveniently, most cell cycle genes are present in only one copy.
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