ANALYSIS OF G-ALPHA-4, A G-PROTEIN SUBUNIT REQUIRED FOR MULTICELLULAR DEVELOPMENT IN DICTYOSTELIUM

The Dictyostelium G-alpha-4 gene encodes a G-protein alpha-subunit that is primarily expressed during the multicellular stages of development. g-alpha-4 null mutants, created by gene disruption, show aberrant morphological differentiation, reduced levels of prespore gene expression, and a loss of the ability to produce spores. These developmental phenotypes can be rescued by complementation with the wild-type gene. Cells that overexpress the G-alpha-4 gene (G-alpha-4HC) also show reduced spore production but display an aberrant morphological phenotype distinct from that of g-alpha-4 cells. The g-alpha-4 phenotype can be partially rescued by the presence of wild-type or G-alpha-4HC cells in chimeric organisms, suggesting that G-alpha-4-expressing cells produce an intercellular signal that is essential for multicellular development.