Fig. 2. Constitutively active Drac1 transgene expression causes contraction of the amnioserosa. Embryos were stained with phalloidin to detect F-actin (A) or with the anti-phosphotyrosine antibody (B-D). (A) An early stage 14 GAL4^332.3;UAS-Drac1V12 embryo showing dramatic contraction of amnioserosa into the rear half of dorsal hole. (B) A stage 15 GAL4^332.3;UAS-Drac1V12 embryo late in dorsal closure showing bunched closure of the epidermis around contracted amnioserosa. Phosphotyrosine staining in the amnioserosa is very intense. (C) An early stage 14 Hs-GAL4^M-4/UAS-Drac1V12 embryo showing an amnioserosa phenotype similar to that in A. Attachments of the amnioserosa to the epidermis can be seen (arrowhead). (D) Late stage 14 Hs-GAL4^M-4/UAS-Drac1V12 embryo showing bunched closure of the epidermis around contracted amnioserosa.