Fig. 4.

che-1 is required to amplify its own expression in the embryo. (A) Quantification of che-1(ot856[che-1::gfp]) fluorescence intensity in wild type, che-1(ot908 ot856), che-1(ot871 ot856) and che-1(ot63 ot941) mutants. Fluorescence intensity was analyzed at different embryonic stages: pre-bean, bean, comma, 1.5-fold, 2-fold and 3-fold. The data are presented as individual values with each dot representing the expression level of one neuron with the mean±s.e.m indicated. Two-way ANOVA followed by Tukey's multiple comparisons test; **P<0.01, ***P<0.001. n≥13 for all genotypes. a.u., arbitrary units. (B,C) Conceptualization of the function of autoregulation. (B) In this scenario, autoregulation is required only for maintenance of the cellular state. The initiation phase of che-1 induction triggers sufficiently high levels of che-1, effector gene activation and cellular differentiation occurs normally, and autoregulation is exclusively required to maintain the differentiated state. (C) In this scenario, found to apply here to che-1, autoregulation is also required for the boosting of initial transcription factor expression, ensuring initial activation of the effector battery and, later, maintaining transcription factor expression to ensure continuous effector gene expression.