The ectomycorrhizal symbiosis: genetics and development

Ectomycorrhiza represents a symbiotic structure made between tree roots and filamentous hyphae. This new organ results from a favourable interaction between plant and microbes, taking place in the soil at the vicinity of the root. Diversity is extremely important in the rhizosphere, with large numbers of bacterial, fungal, nematode and invertebrate species. Therefore, partners of the mycorrhiza have to recognize each other and they do it by using diffusible rhizospheric molecules. This recognition leads to cellular interactions between root and fungal cells, driven by changes in gene and protein expression. The aim of this review is to describe the cellular, genetic and molecular events leading to the formation of the ectomycorrhizal tissues with an emphasis on gene expression and cell-to-cell communication.