Fig. 5.

Model for molecular switch controlling gld-1 mRNA. (Upper) Diagram of distal germ line. DTC is the somatic distal tip cell that provides the niche for germ-line stem cells; the mitotic region spans the extent of any mitotically dividing germ cells; the transition zone includes nuclei in early stages of meiotic prophase; and the switch region contains nuclei transitioning from mitotic to meiotic cell cycle. Solid yellow, FBF promotes continued mitotic divisions; solid green, GLD proteins promote meiosis; gradient from yellow to green, transition from mitosis to meiosis. (Lower) FBF repression of gld-1 mRNA (Left), and GLD-2 activation of same mRNA (Right). FBE, FBF-binding element in the gld-1 3′ untranslated region. Figure is not to scale.