Environmental factors inducing sexual development inDictyostelium discoideum

In the heterothallic strains NC4 and HM1 ofDictyostelium discoideum, sexual development is initiated by the formation of diploid zygotic giant cells produced through the fusion of these two opposite mating-type haploid cells. For sexual cell fusion, amoeboid cells must first acquire fusion competence, which requires culture under certain environmental conditions, such as darkness, excessive water, and sufficient bacteria as food. However, in the subsequent stages of cell fusion and development of the giant cells into mature macrocysts, cells do not require the above conditions. Cell fusion and development into macrocysts were able to occur even in light with minimum water and in the absence of bacteria. For cell fusion calcium ions were required.