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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.
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