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<p><i>Bidens pilosa</i> is widely recognized as a cadmium (Cd) hyperaccumulator with potential for phytoremediation. Exogenous melatonin can enhance plant Cd tolerance, thereby improving phytoremediation efficiency. However, the biochemical and molecular mechanisms by which melatonin enhances Cd tolerance in <i>B</i>. <i>pilosa</i> remain unclear. This study examines the mechanisms by which melatonin alleviates Cd toxicity in <i>B</i>. <i>pilosa</i>, focusing on growth attributes, antioxidant activity, Cd accumulation, and the expression of Cd stress-related genes. The results show that the application of 100 μM melatonin significantly alleviates the inhibitory effects of Cd toxicity on the growth of <i>B</i>. <i>pilosa</i> seedlings, with fresh weight and root length being 2.71 and 2.14 times higher, respectively, compared to the Cd-only treatment group. The degradation of photosynthetic pigments was also effectively mitigated. The application of 100 μM melatonin significantly reduced the Cd-induced increases in malondialdehyde (MDA) and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) levels by 62.50% and 62.92%, respectively. It also modulated the levels of non-enzymatic antioxidants such as total phenols and total flavonoids, enhanced the activity of antioxidant enzymes by 1.15–1.70 times that under Cd stress, and upregulated the expression of antioxidant enzyme-related genes, including <i>BpPOD</i> and <i>BpSOD</i>. The expression levels of <i>BpPOD</i> and <i>BpSOD</i> reached their highest, being 1.32 times and 1.57 times that under Cd stress, respectively. These results indicate that melatonin effectively alleviates Cd-induced oxidative damage in <i>B</i>. <i>pilosa</i>. Furthermore, 100 μM melatonin reduced Cd content in the shoots of seedlings by 25.50%. Notably, melatonin significantly increased the proportion of Cd in the cell wall and soluble fractions and facilitated the transformation of Cd from highly toxic to less toxic forms. Melatonin also maintained mineral nutrient balance in seedlings under Cd stress by regulating the expression of <i>BpPCS1</i> and <i>BpZIP6</i>. In conclusion, exogenous melatonin exhibits multiple beneficial effects in mitigating Cd toxicity in <i>B</i>. <i>pilosa</i> seedlings. Growth inhibition caused by heavy metal toxicity remains a major constraint on the application of hyperaccumulator plants for phytoremediation. The application of melatonin may serve as an effective strategy to enhance the phytoremediation potential of plants under high concentrations of heavy metal contamination.</p>

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Melatonin Enhances Cadmium Tolerance in Bidens pilosa via Integrated Regulation of Antioxidant Activity, Metal Distribution, and Stress-Responsive Genes

  • 期刊论文

  • 发表日期：

    2025年9月2日

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  • Yingying Hu,
  • Yannan Wang,
  • Jincen Liu,
  • Kejin Song,
  • Tengfei Ma,
  • Ji Chen,
  • Shunqin Zhu,
  • Wanhong Liu

摘要

Bidens pilosa is widely recognized as a cadmium (Cd) hyperaccumulator with potential for phytoremediation. Exogenous melatonin can enhance plant Cd tolerance, thereby improving phytoremediation efficiency. However, the biochemical and molecular mechanisms by which melatonin enhances Cd tolerance in B. pilosa remain unclear. This study examines the mechanisms by which melatonin alleviates Cd toxicity in B. pilosa, focusing on growth attributes, antioxidant activity, Cd accumulation, and the expression of Cd stress-related genes. The results show that the application of 100 μM melatonin significantly alleviates the inhibitory effects of Cd toxicity on the growth of B. pilosa seedlings, with fresh weight and root length being 2.71 and 2.14 times higher, respectively, compared to the Cd-only treatment group. The degradation of photosynthetic pigments was also effectively mitigated. The application of 100 μM melatonin significantly reduced the Cd-induced increases in malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels by 62.50% and 62.92%, respectively. It also modulated the levels of non-enzymatic antioxidants such as total phenols and total flavonoids, enhanced the activity of antioxidant enzymes by 1.15–1.70 times that under Cd stress, and upregulated the expression of antioxidant enzyme-related genes, including BpPOD and BpSOD. The expression levels of BpPOD and BpSOD reached their highest, being 1.32 times and 1.57 times that under Cd stress, respectively. These results indicate that melatonin effectively alleviates Cd-induced oxidative damage in B. pilosa. Furthermore, 100 μM melatonin reduced Cd content in the shoots of seedlings by 25.50%. Notably, melatonin significantly increased the proportion of Cd in the cell wall and soluble fractions and facilitated the transformation of Cd from highly toxic to less toxic forms. Melatonin also maintained mineral nutrient balance in seedlings under Cd stress by regulating the expression of BpPCS1 and BpZIP6. In conclusion, exogenous melatonin exhibits multiple beneficial effects in mitigating Cd toxicity in B. pilosa seedlings. Growth inhibition caused by heavy metal toxicity remains a major constraint on the application of hyperaccumulator plants for phytoremediation. The application of melatonin may serve as an effective strategy to enhance the phytoremediation potential of plants under high concentrations of heavy metal contamination.