Isolation and characterization of a rice cDNA encoding B1-type cyclin-dependent kinase

Cyclin-dependent kinases (CDKs) are central players that control the cell cycle. In plants, A- and B-type CDKs are directly involved in cell cycle regulation. B-type CDK (CDKB) is unique to plants; however, only limited information on this kinase has been accumulated thus far. In the present study, we identified a rice cDNA encoding CDKB1;1 and studied its expression in suspension-cultured cells and plant tissues. We found that this enzyme was expressed in actively dividing cells in suspension cultures and was downregulated by the depletion of sucrose from the medium. In plants, the CDKB1;1 transcripts were highly expressed in the shoot and root apical meristems, but not in mature plant organs. These results suggested that CDKB1 is mainly involved in mitotic cell division during plant development.