Cross talks at the morphogenetic, physiological and gene regulation levels between the mycobiont Piloderma croceum and oak microcuttings (Quercus robur) during formation of ectomycorrhizas.

Ectomycorrhiza, a symbiosis between soil fungi and the rootlets of major forest trees, is characterized by well defined anatomical traits but also encompasses a wide range of ecological and physiological situations. Functional studies of this symbiosis therefore address different kinds of systems. Here we review works done on an experimental model with micropropagated oak cuttings infected in a Petri dish system with the basidiomycote Piloderma croceum. The model is characterized by a high demand for carbohydrates by the fungus and the only differentiating of mycorrhizas with plants having a sufficient carrying capacity in terms of photoassimilate production. Already during the pre-mycorrhizal stage symbiotic interactions between the partners are observed at the morphogenetic and physiological levels and are influenced by the typical endogenous rhythmic development of the plant with alternating growth flushes in the shoot and in the roots. The system was used for first molecular and transcriptomic studies based on a subtractive suppressive hybridization, a macro-array experiment and the research for specific genes.