Abstract
The Cdc25 protein phosphatase is a key enzyme involved in the regulation of the G2/M transition in metazoans and yeast. However, no Cdc25 ortholog has so far been identified in plants, although functional studies have shown that an activating dephosphorylation of the CDK-cyclin complex regulates the G2/M transition. In this paper, the first green lineage Cdc25 ortholog is described in the unicellular alga Ostreococcus tauri. It encodes a protein which is able to rescue the yeast S. pombe cdc25-22 conditional mutant. Furthermore, microinjection of GST-tagged O. tauri Cdc25 specifically activates prophase-arrested starfish oocytes. In vitro histone H1 kinase assays and anti-phosphotyrosine Western Blotting confirmed the in vivo activating dephosphorylation of starfish CDK1-cyclinB by recombinant O. tauri Cdc25. We propose that there has been co-evolution of the regulatory proteins involved in the control of M-phase entry in the metazoan, yeast and green lineages. Link to supplemental material:http://www.landesbioscience.com/journals/cc/khadarooCC3-4-sup.pdf
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