An APM-1 hybrid protein can complement UNC-101
proteins in vulval development: The apm-1 hybrid gene
can rescue the suppression of vulvaless phenotype of
unc-101(sy108). The animals in the photographs are at
the L3 molt stage, which corresponds to the period of vulval induction.
The arrowheads indicate the locations of the anchor cell that induces
the vulval precursor cells (VPCs). The lines indicate the lineage of
each VPC. The genotypes are: (A) wild-type; (B)
let-23(sy1); (C) unc-101(sy108);
let-23(sy1); (D) unc-101(sy108);
let-23(sy1)::unc-101 minigene; (E)
unc-101(sy108);let-23(sy1)::apm-1 hybrid gene;
and (F) unc-101(sy108);let-23(sy1)::apm-2 hybrid
gene. (A), wild-type vulval induction in which three vulval
precursor cells (VPCs) have divided twice to make four progeny each.
(B) There is no vulval induction because of the reduction-of-function
mutation in the let-23EGFR gene. All VPCs have divided
only once. (C) The unc-101 mutation suppresses the
let-23(sy1) vulvaless mutant phenotype to
greater-than-wild-type vulval induction. Four VPCs, instead of three
VPCs as in normal induction, have divided twice. (D) The transgenic
unc-101 minigene rescued the endogenous unc-101
(sy108) mutation, and thus no vulval induction occurred, as in
the single mutant of let-23(sy1). (E) The
apm-1 hybrid gene complemented the endogenous
unc-101 (sy108) mutation, thus no vulval induction
occurred, as in the single mutant of let-23(sy1). (F)
Four VPCs were induced because the apm-2 hybrid gene
could not complement the endogenous unc-101 (sy108)
mutation. This phenotype is identical to that of unc-101(sy108);
let-23(sy1) mutant animals. The scale bar is 10 μm.