Arbuscular mycorrhizal fungi (AMF) establish symbiotic interaction with 80% of known land plants. It has a pronounced impact on plant growth, water absorption, mineral nutrition, and protection from abiotic stresses. Plants are very dynamic systems having great adaptability under continuously changing drying conditions. In this regard, the function of AMF as a biological tool for improving plant drought stress tolerance and phenotypic plasticity, in terms of establishing mutualistic associations, seems an innovative approach towards sustainable agriculture. However, a better understanding of these complex interconnected signaling pathways and AMF-mediated mechanisms that regulate the drought tolerance in plants will enhance its potential application as an innovative approach in environmentally friendly agriculture. This paper reviews the underlying mechanisms that are confidently linked with plant–AMF interaction in alleviating drought stress, constructing emphasis on phytohormones and signaling molecules and their interaction with biochemical, and physiological processes to maintain the homeostasis of nutrient and water cycling and plant growth performance. Likewise, the paper will analyze how the AMF symbiosis helps the plant to overcome the deleterious effects of stress is also evaluated. Finally, we review how interactions between various signaling mechanisms governed by AMF symbiosis modulate different physiological responses to improve drought tolerance. Understanding the AMF-mediated mechanisms that are important for regulating the establishment of the mycorrhizal association and the plant protective responses towards unfavorable conditions will open new approaches to exploit AMF as a bioprotective tool against drought.

• We measured the influences of soil fertility and plant community composition on Glomeromycota, and tested the prediction of the functional equilibrium hypothesis that increased availability of soil resources will reduce the abundance of arbuscular mycorrhizal (AM) fungi. • Communities of plants and AM fungi were measured in mixed roots and in Elymus nutans roots across an experimental fertilization gradient in an alpine meadow on the Tibetan Plateau. • As predicted, fertilization reduced the abundance of Glomeromycota as well as the species richness of plants and AM fungi. The response of the glomeromycotan community was strongly linked to the plant community shift towards dominance by Elymus nutans. A reduction in the extraradical hyphae of AM fungi was associated with both the changes in soil factors and shifts in the plant community composition that were caused by fertilization. • Our findings highlight the importance of soil fertility in regulating both plant and glomeromycotan communities, and emphasize that high fertilizer inputs can reduce the biodiversity of plants and AM fungi, and influence the sustainability of ecosystems.

Summary: Nitrogen (N) availability is increasing dramatically in many ecosystems, but the influence of elevated N on the functioning of arbuscular mycorrhizal (AM) fungi in natural ecosystems is not well understood. We measured AM fungal community structure and mycorrhizal function simultaneously across an experimental N addition gradient in an alpine meadow that is limited by N but not by phosphorus (P). AM fungal communities at both whole‐plant‐community (mixed roots) and single‐plant‐species (Elymus nutans roots) scales were described using pyro‐sequencing, and the mycorrhizal functioning was quantified using a mycorrhizal‐suppression treatment in the field (whole‐plant‐community scale) and a glasshouse inoculation experiment (single‐plant‐species scale). Nitrogen enrichment progressively reduced AM fungal abundance, changed AM fungal community composition, and shifted mycorrhizal functioning towards parasitism at both whole‐plant‐community and E. nutans scales. N‐induced shifts in AM fungal community composition were tightly linked to soil N availability and/or plant species richness, whereas the shifts in mycorrhizal function were associated with the communities of specific AM fungal lineages. The observed changes in both AM fungal community structure and functioning across an N enrichment gradient highlight that N enrichment of ecosystems that are not P‐limited can induce parasitic mycorrhizal functioning and influence plant community structure and ecosystem sustainability.

Diversity of arbuscular mycorrhizal fungi (AMF) is well studied in many ecosystems, but little is known about AMF in cold-dominated regions with very