RECEPTOR SERINE THREONINE KINASES IMPLICATED IN THE CONTROL OF DROSOPHILA BODY PATTERN BY DECAPENTAPLEGIC/

Members of the TGF beta superfamily of secreted signaling molecules re gulate growth and cellular patterning during development and interact with specific type I and type II membrane receptors possessing a cytop lasmic serine/threonine kinase domain. We describe two members of the type I receptor family in Drosophila and demonstrate that they are enc oded by the genes saxophone (sax) and thick veins (tkv). Further, we s how that mutations that abolish sex or tkv activity cause phenotypes s imilar to partial or complete loss of activity, respectively, of the T GF beta homolog decapentaplegic (dpp). We propose that specification o f distinct cell fates in response to different concentrations of dpp m ay be achieved combinatorially by the sax and tkv receptors.