FUNCTION OF PROTEIN KINASE-A IN HEDGEHOG SIGNAL-TRANSDUCTION AND DROSOPHILA IMAGINAL DISC DEVELOPMENT

Reduced protein kinase A (PKA) activity in anterior imaginal disc cell s leads to cell-autonomous induction of decapentaplegic (dpp), wingles s (wg), and patched (ptc) transcription that is independent of hedgeho g (hh) gene activity. The resulting nonautonomous adult wing and leg p attern duplications are largely due to induced dpp and wg expression a nd resemble phenotypes elicited by ectopic hh expression. Inhibition o f PKA in anterior cells close to the posterior compartment can substit ute for hh activity to promote growth of imaginal discs, whereas overe xpression of PKA can counteract transcriptional induction of ptc by hh in these cells. PKA therefore appears to be an integral component of the mechanism by which hh regulates the expression of key patterning m olecules in imaginal discs.