MEIOSIS TO MITOSIS TRANSITION REQUIRES MAB1 FUNCTION
Transition from meiotic to mitotic divisions directly leads to the onset of embryogenesis in animals. By contrast, plant meiospores first develop into the haploid generation of the gametophyte, requiring additional mitotic divisions. On pages 4974–4991, Juranić et al. report that a protein homologous to a key animal protein regulating meiosis–mitosis transition is required to organize the second meiotic and first mitotic spindle apparatus in maize. Silencing of the germ line–specific MATH-BTB domain gene MAB1 causes defects in spindle organization together with chromosome loss during meiotic divisions and failure to establish germ cell fate during the first asymmetric mitotic divisions in both germ lines. The cover image shows a tetrad of maize microspores with fluorescently labeled microtubules and DAPI-stained nuclei.