Identification of STKA-dependent genes in Dictyostelium discoideum

During culmination of Dictyostelium aggregates, prespore and prestalk cells undergo terminal differentiation to form spores and a cellular stalk. Disr uption of the cell-fate gene stkA leads to a phenotype in which all the cel ls destined to become spores end up as stalk cells. 'Stalky' mutants expres s normal levels of prespore cell transcripts but fail to produce the culmin ation-stage spore transcript spiA. The stkA gene encodes a putative GATA-ty pe transcription factor (STKA). III order to identify possible downstream t argets of STKA we used the technique of mRNA differential display and isola ted four cDNA fragments that hybridise to mRNAs present during the later st ages of development. All four gene tags were cloned and sequenced. mRNAs re presented by these four sequence tags do not accumulate during culmination of 'stalky' cells and therefore must be specific to the spore pathway. By s creening a cDNA library, longer cDNAs for all four mere cloned and sequence d. Three of these contained complete protein-coding regions while only a pa rtial cDNA was recovered for the fourth. One of the corresponding proteins has significant homology to a surface zinc metalloproteinase (GP63) of the protozoan parasite Leishmania, while another is closely related to a human pre-RNA binding protein (hnRNP R).