RETINOBLASTOMA RELATED1 mediates germline entry in Arabidopsis

Germ cells on demand Unlike animals, plants do not set aside a germline. Instead, germ cells are developed on demand from somatic lineages. Zhao et al. examined the regulatory pathways that manage the transition from somatic to germ cell development in the small plant Arabidopsis (see the Perspective by Vielle-Calzada). The transcription factor WUSCHEL (WUS) was needed early on for development of ovules. Soon after, a trio of inhibitors that work through a cyclin-dependent kinase allowed a transcriptional repressor to down-regulate WUS. This opened the door to meiosis, while restricting the number of reproductive units per seed to one. Science , this issue p. eaaf6532 ; see also p. 378