The Dictyostelium fruiting body assumes its final shape due to the ordered maturation of prestalk and prespore cells during culmination. Prestalks mature into stalk cells at the growing tip of the stalk and prespores into spores when the stalk is about half completed. An unknown inductive signal is implicated in both cases. Mutants have been identified in the host laboratory where stalk and spore cells differentiate prematurely . Two of the mutated genes are: (1) regulatory subunit of pkA; (2) a composite protein (regA) with phosphodiesterase and response-regulator domains, the latter characteristic of histidine kinase / two-component systems. Thus it is proposed that terminal differentiation is controlled through a histidine kinase and cAMP phosphodiesterase that regulate pkA activity. I wish to discover more about this regulatory pathway. First, I shall study the regA protein, to determine whether phosphorylation activates or inactivates the phosphodiesterase and I shall determine the phenotype of cells expressing the activated form of the protein. Second, I shall use insertional mutagenesis and a poweful selection to identify further mutants of the regA class. These will be studied and the genes cloned by conventional techniques. Third, I shall seek mutants with phenotypes similar to that of activated-regA, to identify positively acting components of the pathway.
I already have a good grounding in biochemistry and I now wish to learn molecular genetic techniques and expand my interests to the development of Dictyostelium, in which the host laboratory is a world-leader. I also hope to benefit by experiencing a different scientific culture.