Glutathione mitigates aluminum toxicity in root-apex transition zone of rice through reducing aluminum absorption and maintaining redox balance

Abstract

Aluminium (Al) toxicity is recognized as a major constraint on crop growth and production in acidic soils, and the transition zone (TZ) of plant root apex emerges as the major perception site of Al toxicity. Glutathione (GSH) is reported to be involved in plant responses to various abiotic stresses, but its role and mechanism under Al stress remain unknown. Here, we found that GSH significantly mitigated Al toxicity on rice as revealed by the promotion of root elongation, reduction of oxidative stress and Al absorption. GSH application scavenged Al-induced H₂O₂ burst by activating the ascorbate (AsA)-GSH cycle and proline synthesis in root-apex TZ, thereby alleviating oxidative stress. GSH effectively reduced Al-induced pectin increment and inhibits the H₂O₂-induced pectin methylesterase (PME) activity and demethylesterification degree in root-apex TZ, leading to a reduction in Al binding sites and subsequently Al deposition in cell walls, thereby attenuating the inhibitory effect of Al toxicity on cell elongation. In addition, GSH-derived phytochelatins (PCs) promoted the vacuolar Al sequestration in root-apex TZ, which alleviated Al toxicity to the cytoplasm. Taken together, our results indicate a mechanism underlying how GSH alleviates Al toxicity through influencing redox state and Al absorption in rice root-apex TZ.