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 (EM) represent a highly differentiated interface between soil fungi and tree rootlets enabling symbiotic exchanges of nutrients and water. Mechanisms ruling EM formation were analyzed on in vitro propagated oaks inoculated with the fungus Piloderma croceum. In early phases of the interaction at which EM were not yet differentiated, the fungus promoted plant development, triggered photoassimilation, and plant genes related to symbiosis were found regulated. These early cross talks at different levels were influenced by the plant endogenous rhythmic growth and it appeared that fully differentiation of EM tissues is conditioned by the reaching of a certain carrying capacity by the plant.