There are multiple MAPKs in eukaryotes. In Drosophila, two pathways have been identified. Both proteins are required for dorsal closure, the sealing of the dorsal region of the embryo late in embryonic development.
Dorsal closure involves coordinate cell shape changes of ectodermal cells.
Both DJNK and DJUN are activated in the the immune response of the fly. DJNK is closely associated on chromosome 2 with dror , a Drosophila receptor tyrosine kinase homolog of vertebrate TRK kinases, which mediate responses to neurotropins. Close chromosomal linkage often, but not always, occurs as a consequence of shared developmental function. It is thought that this cell mobility kinase cascade provides feedback information to the nucleus about changes in the cytoskeleton. In addition the JNK-MAP kinase cascade transduces stress related assaults such as bacterial infection to the nucleus, where these signals activate the immune response.