MOLECULAR LESIONS ASSOCIATED WITH ALLELES OF DECAPENTAPLEGIC IDENTIFYRESIDUES NECESSARY FOR TGF-BETA BMP CELL SIGNALING IN DROSOPHILA-MELANOGASTER/

We have identified the molecular lesions associated with six point mut ations in the Drosophila TGF-beta homologue decapentaplegic (dpp). The sites of these mutations define residues within both the pro and liga nd regions that are essential for dpp function in vivo. While all of t hese mutations affect residues that are highly conserved among TGF-bet a superfamily members, the phenotypic consequences of the different al leles are quite distinct. Through an analysis of these mutant phenotyp es, both in cuticle preparations and with molecular probes, we have as sessed the functional significance of specific residues that are conse rved among the different members of the superfamily. In addition, we h ave tested for conditional genetic interactions between the different alleles. We show that two of the alleles are temperature sensitive for the embyronic functions of dpp, such that these alleles are not only embryonic viable as homozygotes but also partially complement other dp p hypomorphs at low temperatures. Our results are discussed with regar d to in vitro mutagenesis data on other TGF-beta-like molecules, as we ll as with regard to the regulation of dpp cell signaling in Drosophil a.