Fig. 9. chordin mRNA injection can block the activity of injected scw mRNA but not that of injected dpp mRNA. (A-D) Lateral views of stage 13 Df(2L)OD16 P[Kr-lacZ] embryos lacking scw. Each embryo was injected dorsally with a different combination of mRNAs before the blastoderm stage and stained for ß-galactosidase activity. (A) Injection of 30 ng/µl of scw mRNA resulted in restoration of amnioserosa in 81% (n=114) of scw embryos. (C) Co-injection of 4.5 µg/µl of chd mRNA completely abolished the ability of injected scw mRNA to restore amnioserosa (0%; n=107). (B) Injection of 370 ng/µl of dpp mRNA resulted in restoration of amnioserosa in 83% (n=83) of scw embryos, however, co-injection of 4.5 µg/µl of chd mRNA with the dpp mRNA (D) was not sufficient to block amnioserosa formation (85%; n=68).