Enhanced abiotic stress tolerance in Arabidopsis overexpressing Ricinus communis FeSOD8 (RcFeSOD8)

Ricinus communis L. is a globally relevant industrial oilseed crop mostly cultivated in tropical arid/semi-arid areas, where abiotic stresses frequently limit crop establishment and productivity. Superoxide dismutase (SOD) is an antioxidant enzyme acting as a primary defense against oxidative stress in plants subjected to abiotic stresses, localized in various subcellular compartments, and classified in eukaryotes according to metal cofactors. In this study, the R. communis RcFeSOD8 gene was characterized, and its physiological, biochemical, and metabolic protective roles investigated through overexpression in Arabidopsis thaliana. RcFeSOD8 was strongly induced under heat stress in R. communis during germination and seedling growth (leaves). Arabidopsis lines overexpressing RcFeSOD8 exhibited improved germination under drought, salinity, and heat stress, along with increased activities of other antioxidant enzymes, higher chlorophyll content, and enhanced thermotolerance. PLS-DA-based metabolomic analysis revealed a clear separation between germinating A. thaliana wild type (WT) and overexpressing lines (OE) under heat and saline stresses. Differential accumulation of key amino acids (threonine, valine, isoleucine, sarcosine, and glycine) as well as sucrose was observed in germinating OE lines compared to WT under stress conditions, suggesting a role for RcFeSOD8 in modulating carbon and nitrogen metabolism, possibly contributing to redox homeostasis by protecting amino acid biosynthetic pathways from oxidative damage. Our findings indicate that RcFeSOD8 enhances tolerance to heat, drought, and salinity during germination and early seedling establishment, making it a promising candidate for molecular breeding programs aimed at improving abiotic stress resilience in R. communis.