MsDUF3700 overexpression enhances aluminum tolerance in alfalfa shoots.

Key message: This study identified a gene associated with aluminum stress through GWAS, which regulates aluminum tolerance in alfalfa by contributing to the antioxidant system. Aluminum (Al) ions precipitate in acidic soils with a pH < 5.5, where they are absorbed alongside other nutrients by plants, negatively impacting plant growth. Alfalfa, the most widely grown perennial legume forage in the world, is especially vulnerable to acidic soil conditions. Our research pinpointed MsDUF3700 as a potential gene linked to Al-response traits via genome-wide association analysis in Medicago sativa. MsDUF3700 encodes the domain of unknown function (DUF). We observed higher expression of MsDUF3700 in Al-tolerant alfalfa compared to Al-sensitive ecotypes. MsDUF3700-overexpressing transgenic alfalfa (MsDUF3700-OE) showed shorter root elongation and higher Al accumulation in roots than wild type (WT) under Al conditions. However, the shoots of MsDUF3700-OE lines showed enhanced growth rates under both normal and Al stress conditions. Under Al stress, MsDUF3700-OE lines showed increased H₂O₂ and malondialdehyde (MDA) levels in the roots, alongside reduced catalase activity, In contrast, the shoots showed an inverse trend. In addition, we found that MsDUF3700-OE alfalfa plants had high Al accumulation in the roots and low Al accumulation in the shoots. Transcripts of MsALS3 and MsPALT1, homologs of Al translocation in alfalfa, were downregulated, while MsNrat1, a homolog of transporters absorb Al, was upregulated in the roots of MsDUF3700-OE in alfalfa. Our research indicates that MsDUF3700 plays a role in aluminum stress by participating in antioxidative defense and facilitating aluminum transport from roots to shoots.