Abstract
Plant cell division is controlled by cyclin-dependent kinases (CDKs), which are activated by binding to cyclins and phosphorylation of the T-loop. Its activity is down-regulated by phosphorylation and binding to CDK inhibitors. However, CDK itself is also quantitatively regulated at the transcriptional and translational levels. We have recently found that B2-type CDK (CDKB2) is degraded by the ubiquitin-proteasome pathway, which responds to DNA damage signaling. CDKB2 is specifically expressed during the G2-to-M phase, thus assumed to play an essential role in the transition to the M phase. Here we shall report how this quantitative regulation is involved in organogenesis during plant development, especially in the process of cell proliferation followed by cell differentiation. We shall also discuss how cell cycle machineries cross talk with signaling pathways associated with genetic programs and phytohormones.
