Molecular Regulation of Arbuscular Mycorrhizal Symbiosis

Abstract

Plant-microorganism interactions at the rhizosphere level have a major impact on plant growth and plant tolerance and/or resistance to biotic and abiotic stresses. Of particular importance for forestry and agricultural systems is the cooperative and mutualistic interaction between plant roots and arbuscular mycorrhizal (AM) fungi from the phylum Glomeromycotina, since about 80% of terrestrial plant species can form AM symbiosis. The interaction is tightly regulated by both partners at the cellular, molecular and genetic levels, and it is highly dependent on environmental and biological variables. Recent studies have shown how fungal signals and their corresponding host plant receptor-mediated signalling regulate AM symbiosis. Host-generated symbiotic responses have been characterized and the molecular mechanisms enabling the regulation of fungal colonization and symbiosis functionality have been investigated. This review summarizes these and other recent relevant findings focusing on the molecular players and the signalling that regulate AM symbiosis. Future progress and knowledge about the underlying mechanisms for AM symbiosis regulation will be useful to facilitate agro-biotechnological procedures to improve AM colonization and/or efficiency.

Arbuscular Mycorrhizal Symbiosis: A Strategy for Mitigating the Impacts of Climate Change on Tropical Legume Crops

“…Mutation in RAM1 and RAM2 showed a reduction in AMF colonization and impaired hyphopodia formation [ 45 ]. The nucleus of the root epidermal cell in contact with the hyphopodium migrates and positions itself underneath the hyphopodium to initiate the formation of the pre-penetration apparatus, a subcellular tube-like structure [ 46 ].…”

“…The pre-penetration apparatus of the host plant allows AMF hypha to grow intracellularly [ 46 ]. When AMF hypha reaches the root cortical cells, it forms an arbuscule (intercellular branching hyphal structure).…”

“…The involvement of plant fatty acid in arbuscule development has been demonstrated in M. truncatula . Medicago truncatula mutant lines defective in two lipid biosynthesis genes FatM and RAM2 showed impaired arbuscule branching [ 46 ]. FatM encodes an ACP-thioesterase, which terminates fatty acid chain elongation and releases 16-carbon fatty acid.…”

Volatile organic compounds shape belowground plant–fungi interactions

“…In the mutualistic association, fungi and plants perceive one another via interacting molecular signals ( Bonfante and Genre, 2015 ). Before physical contact, strigolactones released from host roots in response to inorganic phosphorus starvation induce AM spore germination, hyphae production, and branching to physically contact roots ( Ho-Plágaro and García-Garrido, 2022 ). Moreover, flavonoids, 2-hydroxy fatty acids, polyamines, and cutin monomers are among the active plant compounds influencing hyphal elongation or branching ( Becard et al., 1992 ; Ghachtouli et al., 1995 ; Akiyama et al., 2005 ; Nagahashi and Douds, 2011 ; Wang et al., 2012 ; Gutjahr and Parniske, 2013 ).…”

“…Although important advances in understanding the molecular regulation of AM symbiosis have been achieved ( Ho-Plágaro and García-Garrido, 2022 ), there is little information on VOCs during mycorrhization. Sun et al.…”