Molecular mechanism of cytokinin-activated cell division in <i>Arabidopsis</i>

Cell cycle regulation The hormone cytokinin regulates various aspects of plant development and physiology, largely by managing cell proliferation. Yang et al. show that cytokinin promotes nuclear localization of the transcription factor MYB3R4, which activates the expression of two importins and genes that tip the cell into the next phase of the cell cycle. The importins facilitate further MYB3R4 accumulation within the nucleus, accelerating the progression into mitosis. MYB3R4 and the importins dissipate when the nuclear membrane dissolves at prometaphase, so there is only one round of mitotic activation per cell cycle. Science , this issue p. 1350