Disruption of the gene encoding the p34/31 polypeptides affects growth and development of Dictyostelium discoideum

We have used homologous recombination to disrupt the gene which codes for p34 and p31, two polypeptides related to a cAMP-binding protein (CABP1) in Dictyostelium discoideum. By screening a total of 80 independent transformants by Southern blotting, four mutants have been isolated. Two of these mutants were analyzed in detail. Our results indicate that, while a null allele has not been obtained, both mutants express drastically reduced levels of truncated p34 and p31. Phenotypic analysis has demonstrated that both of them grow significantly more slowly than wild-type controls when bacteria are used as a food source. Interestingly, this growth defect is not seen when the cells are cultured axenically. In addition, the mutants possess an altered developmental profile. They complete development approximately 3 h later than wild-type controls. These results indicate that p34 and p31 play roles in both growth and development in this organism.