The effect of ICK1, a plant cyclin-dependent kinase inhibitor, on mitosis in living plant cells

The inhibitory activity of Arabidopsis thaliana ICK1, a plant cyclin-dependent kinase inhibitor, has previously been characterised by its effect on plant cyclin-dependent kinase activity in vitro and its effect on growth in transgenic plants. Herein, we examine cyclin-dependent kinase-driven cell-cycle events, probed by testing the sensitivity of living cells to introduced ICK1 protein. The microinjection of ICK1 into individual Tradescantia virginiana stamen hair cells during late prophase and prometaphase resulted in a clear protein-specific increase in the metaphase transit time (time from nuclear envelope breakdown to the onset of anaphase) in a manner dependent on load and injection time. The results indicate a continuing role for cyclin-dependent kinases in mitotic progression and provide in vivo evidence at the cellular level that ICK1 can restrict growth in the plant by inhibiting cell division.