THE DROSOPHILA JUN-N-TERMINAL KINASE IS REQUIRED FOR CELL MORPHOGENESIS BUT NOT FOR DJUN-DEPENDENT CELL FATE SPECIFICATION IN THE EYE

We cloned and characterized the Drosophila homolog of mammalian Jun-N- terminal kinases (DJNK). We show that DJNK is encoded by basket (bsk). Like hemipterous (hep), which encodes the Drosophila JNK kinase, bsk is required in the embryo for dorsal closure, a process involving coor dinate cell shape changes of ectodermal cells. Dorsal closure can also be blocked by dominant negative Drosophila cdc42, which has been show n to act upstream of JNKK in vertebrates. Therefore it appears that th e JNK pathway is conserved and that it is involved in controlling cell morphogenesis in Drosophila. Although DJNK efficiently phosphorylates DJun in vitro, bsk function is not required for the specification of cell fate in the developing eye, a process that requires MAP kinase an d DJun function.