The mechanism of the phenylpropanoid biosynthesis pathway in peanut seedlings responding to high Se stress

Excessive selenium (Se) can induce phytotoxicity, inhibit growth and development, and disrupt gene expression and metabolic homeostasis. However, the molecular mechanisms underlying Se-induced responses in peanut seedlings remain unclear. In this study, integrated transcriptome and metabolome analyses were conducted to characterize the responses of peanut leaves and roots to Se toxicity. Se toxicity significantly inhibited root growth, including reductions in total root length and root surface area, and decreased leaf area. It also disrupted antioxidant enzyme balance in both roots and leaves, resulting in malondialdehyde (MDA) accumulation and membrane lipid peroxidation. In addition, Se exposure affected the absorption and transport of essential ions, including Zn, Fe, and B, leading to nutrient metabolism disturbance. Transcriptomic analysis identified 3,578 differentially expressed genes (DEGs) in roots and 1,331 DEGs in leaves, mainly associated with antioxidant regulation, ion transport, and secondary metabolism. Metabolomic analysis detected 582 differentially expressed metabolites (DEMs) in leaves and 846 in roots, including amino acids, fatty acids, and phenolic compounds. Both tissues showed significant enrichment of the phenylpropanoid metabolism pathway under high Se stress. Key biosynthetic genes such as phenylalanine ammonia-lyase ( PAL ), cinnamyl alcohol dehydrogenase (CAD ), and 4-coumarate-CoA ligase ( 4CL ) were differentially expressed, regulating the levels of metabolites such as cinnamic acid and coumaroylquinic acid and thereby mitigating oxidative stress. This study provides a comprehensive analysis of the physiological and molecular responses of peanut seedlings to Se toxicity. It highlights the central role of the phenylpropanoid biosynthesis pathway in maintaining redox balance and improving tolerance to Se stress. The findings offer a theoretical foundation for breeding Se-tolerant peanut varieties.