Crosstalk between glutathione and melatonin in chromium detoxification in sweet potato revealed by high-throughput sequencing and physio-biochemical profiling

Chromium (Cr) contamination severely inhibits plant productivity, primarily by disrupting photosynthetic performance, growth, and inducing oxidative stress. This study investigated the comparative molecular mechanisms by which exogenous glutathione (GSH) and melatonin (MT) confer tolerance to Cr stress in sweet potato using an integrated transcriptomic approach. Transcriptome analysis identified 7,734 differentially expressed genes (DEGs) across Cr stress and mitigator treatments. The GO and KEGG pathway enrichment analyses showed that DEGs were mainly enriched in GO terms, such as photosynthesis, carbon fixation, and cell-wall organization, as well as pathways including MAPK signaling, glutathione metabolism, plant hormone signal transduction, and membrane/vesicle transport. These DEGs were subjected to cluster analysis, and four major expression clusters (C1-C4) were identified, with DEGs ranging from 1,234 to 3,285. GSH-specific protection was associated with Cluster C4, enhancing genes involved in ROS defense, H₂O₂ response, pyruvate metabolism, and ER protein processing, indicating improved redox and metabolic control Network analysis identified 30 potential key hub genes, including the growth regulator <i>GA20OX1</i>, the chlorophyll synthesis enzyme <i>HEMA1</i>, and the vacuolar transport aquaporin <i>TIP2-1</i>. These results suggest that GSH induces a stronger transcriptional response by effectively mitigating Cr-induced damage and strengthening a redox-centered defensive metabolic network. This identifies actionable molecular targets for crop improvement through breeding and genetic engineering.