Fig. 1. A minimal 1.3 kb enhancer in egl-13 URS drives expression specifically in the cell lineage. (A) The cells are singled out from a population of 12 VU intermediate precursors (six on one lateral side are shown, within 5 µm of the midline) surrounding the central AC, and undergo one round of cell division (d., dorsal; v., ventral). Eight descendants plus the AC form the utse syncytium; four descendants become uv1 and are more proximal to the vulva. (B) Medial uterine and vulval morphology. Base, basement membrane. (C) In a lateral plane to B, egl-13::GFP(tyIs4) initiates uterine expression only in the cells and persists in descendants. Fluorescent nuclei are bracketed. Asterisks mark fluorescent nuclei of the body wall. Scale bar: 10 µm. (D) lineage expression of deletion constructs generated from egl-13^FL::GFP. Restriction sites utilized, approximate deletion lengths, and end points as distances from the translational start are indicated.