Tissue-specific metal accumulation and tuber metabolic reprogramming in Cyperus esculentus under multiple-metal stress

Abstract

Understanding plant responses to co-occurring metal contamination is essential for evaluating their phytoremediation potential, yet the physiological and molecular responses of Cyperus esculentus (CES) to combined Cu, Zn, and Cd exposure remain poorly understood. Here, CES plants were exposed to combined Cu, Zn, and Cd stress at concentrations of 0–10 mg/L under hydroponic conditions, and plant growth, tissue-specific metal accumulation, physiological and biochemical responses, and tuber transcriptomic changes were systematically analyzed. Metal accumulation exhibited clear tissue specificity, with roots serving as the primary sites of metal retention, particularly for Cu, while culms accumulated considerable amounts of Zn and Cd and tubers showed comparatively lower but detectable metal accumulation. Increasing metal concentrations progressively inhibited plant growth and enhanced oxidative stress, as indicated by elevated H2O2 and malondialdehyde (MDA) levels, accompanied by stress-dependent adjustments in soluble sugars, reducing sugars, and flavonoids. In tubers, increased soluble sugar accumulation together with the downregulation of carbohydrate catabolism-related genes suggested a shift toward carbon reserve maintenance under metal stress. Under high-concentration exposure, tuber glutathione content increased nearly nine-fold, accompanied by sustained upregulation of a metallothionein-like protein gene and multiple stress-protective genes. These findings indicate that CES exhibits coordinated physiological and transcriptional responses to combined Cu/Zn/Cd stress and suggest that tubers may contribute to stress tolerance through carbon reserve adjustment and a potential glutathione-associated protective response. This study provides physiological and transcriptomic evidence for CES responses to Cu/Zn/Cd co-exposure and supports further evaluation of its phytoremediation potential in metal co-contaminated environments.