Arbuscular mycorrhiza fungi Rhizophagus irregularis regulate iron and zinc homeostasis in tobacco by mediating the expression of Yellow Stripe-Like 7

Abstract

Arbuscular mycorrhizal (AM) participate in fungi-plant symbiotic relationships and mediate the acquisition of soil-borne nutrients by host plants. However, little is known about how AM colonization affects the homeostasis of iron (Fe) and zinc (Zn) in the host plant. Here, we assessed the performance of mycorrhizal growth, oxidative defense, nutrient accumulation, and key gene responses in AM-colonized tobacco (Nicotiana tabacum L.) under different nutrient stress. The total mycorrhizal frequency of AM fungi on tobacco roots reached 86 % and 75 % under low and high phosphorus (P) treatments, respectively. Under Fe/Zn stress, AM alleviated the inhibition of tobacco biomass accumulation, decreased the content of lipid peroxides, and upregulated enzymatic antioxidant capability. In AM-colonized tobacco, Fe/Zn accumulation was increased under deficient conditions and decreased under surplus conditions. Tobacco uptake of P, Fe, and Zn was impaired by excess nutrient concentrations and improved at low concentrations, and this phenomenon was supported by AM colonization. Fe/Zn deficiency upregulated genes related to Fe/Zn uptake, and Fe/Zn excess upregulated genes related to heavy metal efflux, with AM colonization further promoting these upregulations. Notely, we found a possible crosstalk node, Yellow Stripe-Like 7 (NtYSL7), in the AM and Fe/Zn homeostasis regulatory network. NtYSL7 has a plasma membrane-localized oligopeptide transporter domain. NtYSL7 is strongly induced by AM colonization, deficiency of Fe, and surplus Zn, and interacts with many Fe/Zn transporters. AM assists host plants in maintaining Fe/Zn homeostasis by improving nutrient accumulation, redox homeostasis, and transport mechanisms, and NtYSL7 is likely important within the crosstalk network of AM, Fe, and Zn nutrient homeostasis.