In many developing organisms differentiation is regulated by interactions between neighboring cells although the mechanism is not known for any organism. The goal of this study is to isolate the components of a cell interaction system which regulates gene expression and differentiation during the developmental cycle of the myxobacterium Myxococcus xanthus. The spoC locus is involved in the production of an intercellular signal, the SpoC signal, which is necessary for the transcription of specific developmental (SpoC-dependent) genes. This proposal contains three lines of investigation which deal with different aspects of the signaling process. First, the protein product of the spoC locus will be purified by immunoaffinity chromatography. The cellular location of this protein will be determined by western blotting, and a bioassay will be developed for the protein. Second, several SpoC-dependent promoters will be cloned. The nucleotide sequences responsible for their regulation will be identified by DNA sequencing, deletion analysis and mutagenesis. Finally, another genetic locus, which has been shown to modulate expression of SpoC-dependent genes, will be isolated by molecular cloning, and SpoC-dependent promoters in a positive or negative manner. The simple micro-organism, Myxococcus xanthus, provides an excellent model system in which to study the control of a developmental program by cell interactions. It provides a system in which genetic studies can be coupled with studies of cell surface interactions in a developing system.
