pig-1 transcript levels in
sptf-3(
n4850) mutants were decreased by 43% compared to those of wild-type animals, and expression of a Ppig-1::gfp transgene was frequently absent from the seam cells, P cells, ALM neurons and AVM neuron of
sptf-3(
n4850) mutants. Conversely, overexpression of
sptf-3 from a multi-copy transgene under the control of the
sptf-3 promoter induced ectopic expression of
pig-1 in the seam cells and the
hyp7 hypo dermal cells. These results indicate that the consensus SPTF-3 binding motif of the
pig-1 promoter region is required for
pig-1 to promote M4 sister cell death and that SPTF-3 is necessary and sufficient for
pig-1 expression, suggesting that SPTF-3 directly drives
pig-1 expression in the regulation of M4 sister cell death.