Egfr signaling acts upstream of the JNK cascade in dorsal closure.

<p>(A-F) Embryos stained for pMad (red). pMad staining decreases in embryos expressing <i>pnr>Ras</i>^<i>DN</i> (A) and expands in embryo expressing <i>pnr>Hep</i>^<i>Act</i> (B). In embryos co-expressing <i>pnr>Hep</i>^<i>Act</i>; <i>Ras</i>^<i>DN</i>, pMad staining expands (C). pMad staining expands in embryo expressing <i>pnr>Ras</i>^<i>V12</i> (D) and is largely reduced in embryo expressing <i>pnr>Bsk</i>^<i>DN</i> (E). In embryos co-expressing <i>pnr>Bsk</i>^<i>DN</i><i>; Ras</i>^<i>V12</i>, pMad staining is also reduced (F). These results indicate that JNK signaling is epistatic to the Egfr pathway.