Transcriptome and metabolome association analysis revealed key factors involved in melatonin-mediated copper-stress detoxication in tomato

Crops worldwide are increasingly affected by excessive copper (Cu) stress due to pesticide use and industrial pollution, leading to impaired growth and metabolic disturbances. While exogenous melatonin (MT) has been shown to alleviate heavy metal stress, its specific molecular mechanisms in tomatoes remain unclear. This study utilizes transcriptomics and metabolomics to investigate how MT influences gene expression and metabolite accumulation under Cu stress in tomato plants. We found that MT enhances the expression of genes related to lignin synthesis, aiding in Cu sequestration within the cell wall. Additionally, MT boosts glutathione and amino acid levels, increases the expression of GST to chelate metals in cytosol. MT also induces the expression of heat response proteins (HSPs), and promotes the accumulation of flavones and proanthocyanidins to protect the cellular membranes. MT also activates heavy metal transporters for vacuolar metal storage and regulates the transcription factor SlMYB15, which is crucial for Cu stress response. Our findings provide insights into the mechanisms by which MT mitigates Cu toxicity, offering promising implications for breeding Cu-resistant plants.