Fig. 6. dmd-3 and mab-3 occupy the central node of the tail tip retraction network. Our results support a model in which multiple upstream regulatory pathways converge on dmd-3 and mab-3 to regulate the temporal (red), sexual (green) and cell-type (yellow) specificity of tail tip morphogenesis. Temporal specificity is imparted by the heterochronic pathway via let-7 and lin-41. Sexual specificity arises by the regulation of dmd-3 by tra-1, which is likely to be direct. At least two pathways can be thought of as cell-type determinants: the yellow `1' depicts the induction phase of dmd-3 expression in hyp8-11, while the yellow `2' indicates the maintenance and amplification phase. Downstream of dmd-3 and mab-3 lie multiple effectors of morphogenesis, including eff-1. The targets that mediate hyp8-11 retraction are unknown, as is the upstream regulatory pathway that initiates dmd-3 expression (1) in the tail tip. Black arrows and bars indicate regulatory events that are likely to be direct. The solid gray bar indicates indirect regulation. Broken gray and black arrows and bars indicate steps for which the molecular mechanism is unknown. Thin gray arrows indicate that the function of mab-3 in tail tip morphogenesis is secondary to that of dmd-3.