Mycorrhizal ecology and evolution: the past, the present, and the future

Abstract

1406I.1407II.1408III.1410IV.1411V.1413VI.1416VII.14181418References1419 Summary Almost all land plants form symbiotic associations with mycorrhizal fungi. These below‐ground fungi play a key role in terrestrial ecosystems as they regulate nutrient and carbon cycles, and influence soil structure and ecosystem multifunctionality. Up to 80% of plant N and P is provided by mycorrhizal fungi and many plant species depend on these symbionts for growth and survival. Estimates suggest that there are c. 50 000 fungal species that form mycorrhizal associations with c. 250 000 plant species. The development of high‐throughput molecular tools has helped us to better understand the biology, evolution, and biodiversity of mycorrhizal associations. Nuclear genome assemblies and gene annotations of 33 mycorrhizal fungal species are now available providing fascinating opportunities to deepen our understanding of the mycorrhizal lifestyle, the metabolic capabilities of these plant symbionts, the molecular dialogue between symbionts, and evolutionary adaptations across a range of mycorrhizal associations. Large‐scale molecular surveys have provided novel insights into the diversity, spatial and temporal dynamics of mycorrhizal fungal communities. At the ecological level, network theory makes it possible to analyze interactions between plant–fungal partners as complex underground multi‐species networks. Our analysis suggests that nestedness, modularity and specificity of mycorrhizal networks vary and depend on mycorrhizal type. Mechanistic models explaining partner choice, resource exchange, and coevolution in mycorrhizal associations have been developed and are being tested. This review ends with major frontiers for further research.

Root surface as a frontier for plant microbiome research

“…However, many plant species including major crops such as rice, maize, and cereals are colonized by a wide range of fungi, including mutualistic arbuscular mycorrhizae (4,11). Clearly, the simultaneous examination of bacteria and fungi in plant roots deserves further attention.…”

“…A major discovery of the last decade is that numerous organisms of a microbiome (aka microbiota) are not unpretentious background actors. Instead, some microbiota members influence host processes including behavior, appetite, and health in animals (1) and contribute to nutrition and health of plants (2)(3)(4). Recently, the compositions of the plant root-associated microbiota from numerous plant species, including major crops, were revealed using high-throughput DNA sequencing.…”

Regulation of plants' phosphate uptake in common mycorrhizal networks: Role of intraradical fungal phosphate transporters

“…1 AMF colonize simultaneously several plants from the same or different species, 2 and form thereby far-reaching common mycorrhizal networks (CMNs). We are particularly interested in resource exchange within such complex CMNs.…”

High richness of ectomycorrhizal fungi and low host specificity in a coastal sand dune ecosystem revealed by network analysis

“…2014; van der Heijden et al. 2015). Northern forests, generally poor in tree species, can support several hundreds of EM taxa (Trappe 1977; Horton and Bruns 2001).…”

“…Ectomycorrhizal and orchid mycorrhizal symbioses are more balanced with regard to number of fungi and host plants, with, respectively, 20,000 and 25,000 fungal species associating with around 6000 and 20,000–35,000 plant species (reviewed in van der Heijden et al. 2015). Hence, we could expect a higher potential of preferred associations in EM fungi compared to AM fungi.…”