Organ growth and developmental progression must be coordinated with nutritional status. On p. , Stéphane Noselli and co-workers analyse the interplay between systemic nutrient status signalling via the insulin pathway and germline development in Drosophila. In the ovary, follicle cells undergo a mitotic-to-endocycle switch (MES) in their mode of division; this is regulated by Notch-mediated downregulation of the Cut transcription factor. The authors now show that this MES is nutrient dependent: in the ovaries of starved flies, egg chambers pause at the MES, with the Notch pathway active but Cut downregulation blocked. MES pausing is reversible; upon refeeding, egg chambers rapidly move into the endocycle phase. Furthermore, this paused state is regulated by insulin signalling. Insulin pathway mutants enter paused MES even under fed conditions, while activation of the pathway induces progression into endocycle in starved animals. Cross-talk between FoxO (a key transcription factor downstream of insulin signalling), Notch and Cut ensures the nutrient sensitivity and reversibility of the paused state. Thus, this work identifies a checkpoint in the egg chamber that ensures that development is coupled with nutrient availability.
