Roles of Arbuscular Mycorrhizal Fungi for Essential Nutrient Acquisition Under Nutrient Deficiency in Plants

Plants absorb mineral nutrients for growth and development from the soil though their roots; nutrient acquisition is therefore limited by their root area. To improve it, especially in nutrient-poor conditions, many plant species depend on symbiotic interactions with arbuscular mycorrhizal (AM) fungi, which provide essential nutrients obtained through the network of hyphae to the host plants. When nitrogen, phosphate, or sulfur is deficient, plants produce strigolactones, key signaling molecules, to initiate the interaction with AM fungi. Here, first, we introduce the diversity of AM fungi and their host plants. Second, we summarize the structural features of the symbiotic interaction. Third, we describe strigolactone biosynthesis and the symbiosis signaling pathway. Finally, we describe nutrient exchange system between AM fungi and host plants. Overall, we focus on the roles of AM symbiosis for nutrient acquisition in plants and detail the mechanisms. Understanding how plants adapt to their environment in response to deficiency of mineral nutrients could help to improve sustainable agricultural processes, because the use of AM fungi enables crop production in nutrient-poor environments and allows use of pesticides and fertilizers to be reduced.