Cytokinin Activation of Arabidopsis Cell Division Through a D-Type Cyclin

Abstract
Cytokinins are plant hormones that regulate plant cell division. The D-type cyclin CycD3 was found to be elevated in a mutant ofArabidopsis with a high level of cytokinin and to be rapidly induced by cytokinin application in both cell cultures and whole plants. Constitutive expression of CycD3 in transgenic plants allowed induction and maintenance of cell division in the absence of exogenous cytokinin. Results suggest that cytokinin activates Arabidopsiscell division through induction of CycD3 at the G1-S cell cycle phase transition.