Fig. 7.

Mesoderm defects after uniform activation of Htl by Pyr in mesoderm cells. (A-F,H,J,L,N) Pyr was overexpressed in the mesoderm using a twi::Gal4 driver and UAS::Pyr-HA embryos were fixed and stained with the antibodies indicated. (G,I,K,M) Wild-type embryos for comparison. Mesoderm spreading defects in stage 7 (A,C) and stage 9 (B,D) embryos. All mesoderm cells exhibit high levels of MAPK activation at stages 7 (E) and 9 (F). Overexpression of Pyr results in large ectopic Eve-positive clusters at stages 10 and 12 (H and J, respectively, arrowheads; compare with G and I). Cardiac precursors are absent at stage 13/14 (compare K with L, arrowheads). Protrusions at the dorsal edge of the migrating mesoderm (stage 8, arrows in M) are strongly reduced (N). Note that only short filopodia-like protrusions are present (N, arrowheads).