Fig. 1. sna, vnd and sog expression in transgenic embryos with an ectopic, anterior-posterior Dorsal nuclear gradient. Cellularizing mutant embryos were collected from females homozygous for a null mutation in the gastrulation defective (gd) gene. Mutant embryos lack a dorsoventral Dorsal nuclear gradient. The embryos were hybridized with different digoxigenin-labeled antisense RNA probes, and visualized by histochemical staining. Each image is representative of the predominant pattern exhibited in the majority of embryos stained. In addition, at least three independent transgenic lines were analyzed for this and subsequent figures. Embryos are oriented with anterior to the left and dorsal up. (A-C) snail, vnd, and sog patterns, respectively, in mutant embryos. There is no staining above background levels. (D-F) snail, vnd, and sog patterns, respectively, in mutant embryos that contain the Toll^10b transgene [P(bcdToll¹⁰bcd)]. snail expression is detected at the anterior pole, a band of vnd staining is detected in anterior regions (E), and a broad band of sog staining is detected in the anterior third of the embryo (F). The absence of vnd and sog expression at the anterior pole is probably due to repression by Snail (D).