Fig. 2. Ci-FGF3 is expressed in the ventral midline of the nerve cord during notochord CE. (A) Ci-FGF3 in situ showing expression in the floor plate at mid-tailbud stage. (B,C) Cs-FGF3 enhancer::lacZ in situ in late neurula (B; inset, high magnification) and mid-tailbud (C) embryos recapitulates endogenous Ci-FGF3 expression. (D,E) Cross-sectional (D) and lateral (E) views of late neurula embryos double labeled for Cs-FGF3 enhancer (green, lacZ in situ) and Bra::GFP (red, GFP antibody). (F) Cross-sectional view of late neurula embryo stained with phalloidin (green). The notochord plate (dashed line) and floor plate precursors (asterisks) are indicated. (G) Cross-sectional illustration of the organization of major Ciona tissues: ventral nerve cord (red), lateral nerve cord (light blue), dorsal nerve cord (purple), notochord (green), tail muscle (dark blue), endoderm (yellow) and epidermis (brown).