Arbuscular mycorrhizal fungi mitigate Fe deficiency symptoms in sorghum through phytosiderophore-mediated Fe mobilization and restoration of redox status

Sustainable management of iron (Fe) deficiency through the microbial association is highly desirable to ensure crop yield. This study elucidates whether and how arbuscular mycorrhizal fungi (AMF) ameliorate Fe deficiency symptoms in sorghum. AMF inoculation showed a significant improvement in plant biomass, chlorophyll score, Fv/Fm (quantum efficiency of photosystem II), and Pi_ABS (photosynthesis performance index), suggesting its potentiality to diminish Fe deficiency symptoms in sorghum. This AMF-driven prevention of Fe deficiency was further supported by the improvement of biochemical stress indicators, such as cell death, electrolyte leakage, hydrogen peroxide, and superoxide anion. In this study, AMF showed a significant increase in phytosiderophore (PS) release as well as Fe and S concentrations in sorghum under Fe deficiency. Quantitative real-time PCR analysis demonstrated the consistent upregulation ofSbDMAS2(deoxymugineic acid synthase 2),SbNAS2(nicotianamine synthase 2), andSbYS1(Fe-phytosiderophore transporter yellow stripe) in roots due to AMF with Fe deficiency. It suggests that the enhancement of Fe due to AMF is related to the mobilization of Fe(III)-PS in the rhizosphere supported by the long-distance transport of Fe bySbYS1transporter in sorghum. Our study further showed that the elevation of S mainly in the presence of AMF possibly enhances the S-containing antioxidant metabolites (Met, Cys, and GSH) as well as enzymes (CAT, SOD, and GR) to counteract H(2)O(2)and O(2)(-)for the restoration of redox status in Fe-deprived sorghum. Moreover, S possibly participates in Strategy II responses revealing its crucial role as a signaling molecule for Fe homeostasis in sorghum.