The proposed research is based on a unique system of trans-acting lectin regulatory gene mutations in Dictyostelium. The goals of the proposal are to study the role(s) of the lectins in morphogenesis and to examine some novel aspects of developmental gene regulation. The disA and disB mutants fail to express lectin. The drsA mutation supresses disB and renders lectin expression constitutive. Cells carrying the disA mutation are defective in the morphogenetic processes of streaming and chemotaxis. Using an in situ bioassay, Dr. Alexander will determine the specific effects of the disA, disB, and drsA lectin regulatory gene mutations on the capacity of the cells to form streams during aggregation. The distribution of lectin in the cells of the migrating slugs will be determined by immunofluorescent techniques. Dr. Alexander will determine the effect of the drsA suppressor mutation on the pattern of transcription of the lectin genes during growth and development. This will clarify the nature of the phenotypic suppression. He will establish whether strains carrying the mutation are sensistive to the effects of cAMP which is a specific regulator of lectin gene transcription in wild type cells. Genetic methods will be used throughout the study to provide properly constructed experimental and control strains. Dr. Alexander is using the simple model system of the cellular slime mold to study the general developmental problem of trans-acting gene regulation and its relationship to the morphogenesis of multicellular organisms.
