Auxotrophic mutants of Dictyostelium discoideum

Abstract

THE cellular slime mould Dictyostelium discoideum is a unicellular organism in its vegetative stage. On starvation, slime mould amoebae gather into aggregates which pass through a morphogenesis culminating in mature fruiting bodies consisting of dead stalk cells supporting a sphere of viable spores¹. The laboratory strains of D. discoideum are normally haploid, and the genetic techniques available to study cellular differentiation are based on a parasexual system of analysis which includes selection of temperature-resistant diploids after fusion of two haploid strains bearing complementing temperature-sensitive mutations. Recovery of rare haploid segregants is accomplished by selecting recessive drug resistance markers incorporated into one of the parents². The parasexual system suffers from a dearth of selectable markers. The creation of a defined minimal medium³ has made possible the isolation of auxotrophic mutants which we describe here. These auxotrophs should improve linkage analysis by increasing the number of selectable genetic loci and should also prove useful for the selection of diploids and for a variety of biochemical purposes.