Arbuscular mycorrhizal fungi-mediated abiotic stress tolerance: Emerging roles in nutrient exchange, antioxidant defence, and hormonal crosstalk

Abstract

• AMF exchange 80−90 % of P, 20−40 % of N, and 50 % of Zn and Cu, and gets 4−20 % of C. • Through nutrients, AMF mediate antioxidant response and modulate abiotic stress resistance genes. • Antioxidants act as a protector under stress conditions for the biosynthesis of hormones. • Hormones regulate the expression of stress-related genes and influence nutrient transport and antioxidant capacity. • The complex interaction of AMF with hormones varies, where some suppress or promote depending on stress conditions. In the intricate landscape of plant-microbe interactions, arbuscular mycorrhizal fungi (AMF) have emerged as crucial players supporting abiotic stress resistance through various reprogramming processes. Under symbiotic association, plants respond through physiological, biochemical, and molecular mechanisms to minimize damage from abiotic stress and support plant growth. AMF exchanges nutrients by supplying 80−90% of phosphorus, 20−40% of nitrogen, and 50% of zinc and copper via the mycorrhizal pathway, while obtaining 4−20% of carbon from plants. Through nutrients, AMF mediates activation of antioxidant enzymes (e.g., superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) and synthesis of non-enzymatic antioxidants (e.g., glutathione, ascorbic acid, dehydroascorbic acid, and glutathione S-transferase) thereby reducing oxidative stress, maintaining cellular integrity, and regulating the expression of multiple abiotic stress resistance genes through hormones. Additionally, the symbiosis facilitates signalling and modulates phytohormones (e.g., abscisic acid, auxin, salicylic acid, and jasmonic acid), which can influence antioxidant defence and nutrient transport in response to abiotic stress. However, the presence of 255 AMF species alongside various plant species, each showing different mechanisms and complex regulatory interactions related to abiotic stress responses, makes it difficult to evaluate this symbiotic relationship under stress. This review combines recent developments, emphasizing the priming roles of AMF and their species. It offers an overview of nutrient acquisition, its impact on physiological and biochemical responses, and the mechanisms of stress tolerance in different plants. It also provides new insights into mycorrhization by proposing the use of AMF to enhance tolerance to abiotic stress.

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