The adaptable lin-39

Comparative studies of nematode development provide a powerful framework fo r investigating the evolution of developmental mechanisms. A recent report also demonstrates how comparative work can inform our understanding of basi c developmental signaling pathways. In particular, investigation of the dif ferences in vulva development between Caenorhabditis elegans and Pristionch us pacificus has clarified the molecular relationship between an epidermal growth factor-Ras-MAP kinase signaling pathway and downstream Hox transcrip tion factor activity.