Molecular signals required for the establishment and maintenance of ectomycorrhizal symbioses

Abstract

SummaryEctomycorrhizal (ECM) symbioses are among the most widespread associations between roots of woody plants and soil fungi in forest ecosystems. These associations contribute significantly to the sustainability and sustainagility of these ecosystems through nutrient cycling and carbon sequestration. Unfortunately, the molecular mechanisms controlling the mutual recognition between both partners are still poorly understood. Elegant work has demonstrated that effector proteins from ECM and arbuscular mycorrhizal (AM) fungi regulate host defenses by manipulating plant hormonal pathways. In parallel, genetic and evolutionary studies in legumes showed that a 'common symbiosis pathway' is required for the establishment of the ancient AM symbiosis and has been recruited for the rhizobia-legume association. Given that genes of this pathway are present in many angiosperm trees that develop ectomycorrhizas, we propose their potential involvement in some but not all ECM associations. The maintenance of a successful long-term relationship seems strongly regulated by resource allocation between symbiotic partners, suggesting that nutrients themselves may serve as signals. This review summarizes our current knowledge on the early and late signal exchanges between woody plants and ECM fungi, and we suggest future directions for decoding the molecular basis of the underground dance between trees and their favorite fungal partners.

Relationships between plant diversity and soil microbial diversity vary across taxonomic groups and spatial scales

“…For example, we found that tropical forest holds a lower mean total organic carbon (Appendix S2: Fig. The higher mean phosphorus content in the phosphorus significantly impacted plant-microbial correlated sites may reflect the fact that mineral resource of phosphorus nutrient is limited in soil; thus, poor and high phosphorus could directly inhibit microorganisms that can naturally improve phosphorus availability in soils (Gyaneshwar et al 2002, Garcia et al 2015. Tropical forests are organic maters limited ecosystems (Insam andDomsch 1988, Wardle et al 2004), and the ways that organic matter can both retain and release the other nutrients, such as nitrogen and phosphorus, depend on microbial function and activity (Vitousek 1984, Cleveland andLiptzin 2007).…”

Mycorrhizal symbioses and the evolution of trophic modes in plants

“…The establishment and maintenance of mycorrhizal symbiosis is mediated by the complex molecular crosstalk between symbiotic partners (Floss, Levy, Lévesque-Tremblay, Pumplin, & Harrison, 2013;Garcia, Delaux, Cope, & Ane, 2015;Oldroyd, 2013). In general, the evolutionary processes that determine fungal specificity and partner selectivity are not clear.…”

The host plant Pinus pinaster exerts specific effects on phosphate efflux and polyphosphate metabolism of the ectomycorrhizal fungus Hebeloma cylindrosporum: a radiotracer, cytological staining and 31P NMR spectroscopy study

“…The appearance of NMR‐visible polyP, assumed to be short‐chain polyP, in P. pinaster mycelia could be explained by the following sequence of events. The first step would be the release by pine roots of a signal able to elicit a specific response targeting the fungal polyP metabolism, although the nature of this signal has not yet been elucidated (Garcia et al ). The signal appears to be specific of ECM plants as we did not observe the same response with maize plants.…”