Figure 4.

Analysis of the requirement of GATA-binding factors for inducible CecA1 expression in the yolk and epidermis, respectively. Anterior is to the left, and all embryos are in lateral view with dorsal up, except for E which is in ventral view. Embryos were injected with LPS before (A, C, and E) or 12 h after (B, D, and F) egg laying to induce CecA1 expression in the yolk or in the epidermis, respectively. (A–B) β-gal staining in A16 CecA1-lacZ embryos with a mutated GATA site. No expression is observed in the yolk (A), whereas expression in the epidermis is strong (B). (C–F) β-gal expression in A10 CecA1-lacZ embryos in srp^6G mutant background. No CecA1 expression could be detected in the yolk of homozygous srp^6G embryos (C) but is evident clearly in individual cells and in patches of cells in the epidermis (D). The development of the srp^6G embryos (C and D) is arrested, and the embryos do not complete germ-band retraction and dorsal closure as their heterozygous siblings (E and F). In embryos heterozygous for srp^6G and for the ftz-lacZ blue balancer, the β-gal staining is evident both from the CecA1 promoter (arrows) in the yolk (E and F), in the epidermis (F), and from the ftz promoter (arrowheads) in a weak stripe in the anterior part of the embryo (E) and in the ventral nerve chord (E and F; refs. 23 and 24).