AhTGAs coordinate antioxidant defense and metabolic remodeling in peanut under high manganese stress

Abstract

Manganese (Mn) is an essential micronutrient for plant growth, but its excess can cause oxidative stress and inhibit plant growth and development. To reveal the molecular mechanism of peanut response to manganese stress, this study systematically explored the oxidative stress response and metabolic adaptation mechanism of peanuts under manganese stress through transcriptomics and metabolomics analysis. Mn stress significantly induced oxidative damage in peanut leaves, with malondialdehyde (MDA) content increasing by 307.27% and 391.69% under 300 µM and 450 µM Mn treatments, respectively, compared with the control. At the same time, the antioxidant system was widely activated, and the activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and glutathione S-transferase (GST) related enzymes significantly increased. For example, SOD activity increased by 40.39% under 300 µM Mn treatment, and APX activity increased by 59.99% under 450 µM Mn treatment. POD activity significantly increased by 1144.59%, 2212.16% and 3239.19% under 200, 300, and 450 µM Mn treatments, respectively. Metabolomics analysis further revealed that manganese stress significantly altered the metabolic profile of peanuts, especially affecting sulfur-containing metabolism and secondary metabolic pathways. In the cysteine and methionine metabolic pathways, glutathione (GSH) significantly decreased under 300 µM Mn treatment, while Homocysteine significantly increased. Through transcription factor analysis, we identified the AhTGA ( TGA transcription factor ) gene family in peanuts and found that AhTGA1 expression was significantly downregulated under manganese stress. Promoter cis -acting element analysis indicated that AhTGAs were enriched with multiple hormone and stress response-related elements. Notably, all 26 identified AhTGA genes originated exclusively through segmental duplication, and paralogous copies with near-identical protein sequences exhibited divergent stress-responsive expression patterns and cis -element compositions, indicative of subfunctionalization. Among these, AhTGA1.1 ( AhTGA1 ) was identified as a central regulatory hub whose downregulation under Mn stress was significantly correlated with both antioxidant enzyme activation and the dynamic imbalance between GSH consumption and regeneration, revealing that GSH flux rather than steady-state abundance may be the critical determinant of antioxidant capacity. Collectively, these findings suggest that AhTGAs might coordinate antioxidant defense and metabolic remodeling through subgroup-specific regulatory programs, thereby enhancing peanut tolerance to Mn stress. First, segmental duplication has driven the subfunctionalization of AhTGA paralogs, resulting in divergent stress-responsive expression patterns and cis -element compositions despite near-identical protein sequences. Second, AhTGA1 serves as a central regulatory hub that couples Mn stress signaling to antioxidant enzyme activation and sulfur/phenylpropanoid metabolic remodeling, with GSH flux rather than steady-state abundance acting as the critical determinant of antioxidant capacity. These findings provide subgroup-specific TGA targets for developing Mn-tolerant peanut cultivars.