Graviresponses in fungi and slime molds

The analysis of gravisensing in fungi has not yet proceeded as far as in other systems, such as sensory cells for maintenance of equilibrium in crustaceans and vertebrates, Chara rhizoids or plant roots with regard to positive gravitropism. However, considerable progress has recently been made with several fungal systems in the field of graviresponses. This particularly holds true for the molecular basis of primary events. In this review three systems of increasing complexity are considered: the slime molds Physarum and Dictyostelium, which exhibit gravitaxis, the negative gravitropic sporangium of the zygomycete Phycomyces as a single cell structure with the fastest graviresponses known so far, and the fruit bodies of the basidiomycetes Coprinus and Flammulina as highly complex structures with the ability to generate positional information and cell signalling in the context of negative gravitropism.