Figure 4.
med-1 Transgene Expression Correlates with SKN-1 Activity. (A-H) Nuclei stained with 4',6-diamidino-2-phenylindole (DAPI, left column) and anti-cmyc staining (B) or GFP fluorescence (D, F, and H). (A and B) Onset of
med-1::cmyc::MED-1 expression in a six-cell stage embryo. The bright fluorescence in the upper left of (A) is from an adjacent embryo. The faint signal in P2 in (B) is nonspecific, as similar staining occurred in nontransgenic embryos (data not shown). (C-H) Expression of
med-1::GFP::MED-1. (C and D) 8-cell stage; (E and F) 16-cell stage; (G and H) 28-cell stage. (I-O) Expression of a chromosomally integrated
med-1::GFP::MED-1 transgene in mutant backgrounds generated by RNAi. (I) Additional
med-1 expression in the AB lineage in a
mex-1(RNAi) embryo. In
mex-1 mutants, SKN-1 levels become abnormally elevated in AB descendants, causing the granddaughters of AB to adopt MS-like fates and to produce GLP-1-independent pharynx inappropriately (Mello et al., 1992; Bowerman et al., 1993). (J) Expression in all P1 descendants in a
pie-1(RNAi) embryo. SKN-1 is able to activate MS-like and E-like fates in the daughters of P2 when transcription is derepressed in a
pie-1 mutant (Mello et al., 1992). (K) Widespread expression of
med-1 in a par- 1(RNAi) embryo. In
par-1 mutants, misexpression of SKN-1 frequently causes all four-cell stage blastomeres to produce GLP-1-independent pharynx (Bowerman et al., 1993). (L) Expression in descendants of EMS, and at slightly reduced levels in C descendants, in a
sgg-1(RNAi) embryo. (M) and (N)
med-1 expression persists in EMS descendants in mutants lacking either the beta-catenin homolog WRM-1 or the maternal Lef-1-like protein POP-1 (Lin et al., 1995; Rocheleau et al., 1997; Thorpe et al., 1997). (O) Absence of expression in
skn-1(RNAi), a result similar to that seen in
skn-1(
zu67) and
pos-1(RNAi) (data not shown). (P) Overexpression of SKN-1 from an independent hs-
skn-1 extrachromosomal array causes widespread
med-1 expression 90 min after heat shock. Anterior is to the left, and dorsal is up.