Nitrate improves aluminium resistance through SLAH-mediated citrate exudation from roots

Aluminium (Al) toxicity is one of the major constraint for crop production in acidic soil, and the inappropriate utilization of nitrogen fertilizer can accelerate soil acidification. Despite previous studies investigating the regulation of nitrogen forms in Al toxicity of plants, the underlying mechanism, particularly at the molecular level, remains unclear. This study aims to uncover the potentially regulatory mechanism of nitrate (NO₃ ^- ) in the Al resistance of maize and Arabidopsis. NO₃ ^- conservatively improves Al resistance in maize and Arabidopsis, with nitrate-elevated citrate synthesis and exudation potentially playing critical roles in excluding Al from the root symplast. ZmSLAH2 in maize and AtSLAH1 in Arabidopsis are essential for the regulation of citrate exudation and NO₃ ^- -promoted Al resistance, with ZmMYB81 directly targeting the ZmSLAH2 promoter to activate its activity. Additionally, NO₃ ^- transport is necessary for NO₃ ^- -promoted Al resistance, with ZmNRT1.1A and AtNRT1.1 potentially playing vital roles. The suppression of NO₃ ^- transport in roots by ammonium (NH₄ ⁺ ) may inhibit NO₃ ^- -promoted Al resistance. This study provides novel insights into the understanding of the crucial role of NO₃ ^- -mediated signalling in the Al resistance of plants and offers guidance for nitrogen fertilization on acid soils.