Loss of the MAPKKK DLK-1 (
dlk-1(0)), together with
tba-1(gf), resulted in a striking synergistic effect on DD remodeling. In L1 animals of WT,
tba-1(gf),
dlk-1(0) single mutants, and tba- 1(gf)
dlk-1(0) double mutants, DD neurons formed synapses along the VNC. By the adult stage, DD neurons in animals of WT,
tba-1(gf) and
dlk-1(0) single mutants remodeled their synapses and formed new synapses along the DNC. In contrast,
tba-1(gf)
dlk-1(0) adults showed a complete lack of synaptic puncta in the DNC and retained synaptic puncta in the VNC. In >80% of adult
tba-1(gf)
dlk-1(0) animals, synaptic puncta were also retained in the commissures of DD neurons (n > 50 animals), suggestive of a failure in synaptic vesicle transport.