An F-box protein RAE1 regulates the stability of the aluminum-resistance transcription factor STOP1 in Arabidopsis thaliana

Aluminum (Al) toxicity is a major limiting factor on acid soils, which comprise over 30% of the world’s arable land. Some plants have evolved resistance mechanisms to detoxify Al. Arabidopsis thaliana secretes malate via the AtALMT1 transporter to chelate and detoxify Al. The transcription factor STOP1 plays a crucial role in Al resistance mainly through the regulation of AtALMT1 expression. Here, we report the identification and characterization of an F-box protein-encoding gene RAE1 (Regulation of AtALMT1 Expression 1), which is involved in the regulation of STOP1 stability. Mutation of RAE1 causes increased expression of STOP1-regulated genes including AtALMT1 and enhanced Al resistance. RAE1 interacts with STOP1 and promotes the degradation of STOP1 via ubiquitin-26S proteasome pathway, while Al stress stabilizes STOP1. STOP1 upregulates RAE1 expression through direct binding to RAE1 promoter, thus forming a negative feedback loop between STOP1 and RAE1. Our results demonstrate that RAE1 mediates STOP1 ubiquitination and degradation to regulate the expression of STOP1-downstream genes and Al resistance. Identification and characterization of RAE1 may inform strategies to improve crop Al resistance in the future.