Nutritional status must be coupled to stem/progenitor cell proliferation and differentiation to ensure the proper growth and homeostasis of tissues, but how does diet regulate stem cell behaviour? On , E. Jane Albert Hubbard and colleagues show that rsks-1 [the homologue of mammalian p70 ribosomal S6 kinase (S6K), a target of the serine/threonine kinase TOR, which regulates cell growth and proliferation in response to nutritional cues] links cell fate, cell cycle and nutrient response in C. elegans germline stem/progenitor cells. They show that rsks-1 is required germline-autonomously to establish the proper number of germline progenitors, a role that requires a conserved TOR phosphorylation site in RSKS-1. Their analysis also reveals genetic interactions between rsks-1 and Notch, which suggest a prominent role for rsks-1 in cell fate control. Furthermore, dietary restriction causes germline defects similar to those observed in rsks-1 mutants and loss of rsks-1 renders the germline largely insensitive to dietary restriction. The researchers propose, therefore, that TOR-S6K signalling is a key nutrient-responsive regulator of germline progenitors.
