Fig. 3. FRK-1 is required for late epidermal differentiation. (A) Percent of embryos with a wild-type (empty bars) and frk-1(RNAi) (filled bars) genotype expressing the indicated marker. Numbers of frk-1(RNAi) embryos scored are shown above each bar. More than 100 embryos were scored for all markers in wild-type embryos. Seam cell marker (SCM) is a transgenic reporter that expresses a GFP-ß-galactosidase fusion protein specifically in seam cells driven by an uncharacterized promoter (Terns et al., 1997). (B) Nomarski images of mutant and rescued embryos. Expression of the frk-1 coding region from a pan-epidermal promoter, elt-1p, restores enclosure and elongation to homozygous mDf7 embryos. Expression in non-seam epidermis only, using the elt-3 promoter, is not sufficient to allow enclosure or elongation. (C) Genetic model for the pathway of epidermal differentiation, showing position of FRK-1 action based on gene expression data.