Arsenic-induced phytotoxicity in Trigonella foenum-graecum and its regulation by thiol metabolism and ROS quenching enzymes

Arsenic contamination of soils and groundwater affects nearly 106 countries, exposing an estimated 230 million people worldwide to a range of health risks including cancer, cardiovascular disease, diabetes, etc. It also poses significant risks to plants such as inhibited growth, reduced crop yields, and soil health degradation. This study investigates the arsenic (As)-induced changes in dynamics of proteome, sulfur metabolism, antioxidant enzymes and changes in stress tolerance mechanisms in Trigonella foenum-graecum under different concentrations. Hydroponically grown 30-day-old plants were exposed to 0, 25, 50, 75, and 100 µM As for 10 days. The results showed increased oxidative stress and reduced growth at higher As concentrations. Enzymes related to thiol metabolism, including ATP sulfurylase and serine acetyltransferase, were significantly upregulated at 50 and 100 µM As, alongside increased cysteine and glutathione content linked to the upregulation of S-deficiency-induced 2 isoform X2 protein. Antioxidant enzymes (SOD, APX, CAT, GR, GPX, and GST) also exhibited enhanced activity. Proteomic analysis revealed 46 differentially expressed protein spots, including proteins involved in growth and photosynthesis, such as gibberellin 20-oxidase and RuBisCO. Defence proteins like trehalose phosphate phosphatase, calmodulin, and pectinesterase were upregulated, aiding stress tolerance. Sulfur metabolism proteins, such as glutathione S-transferase, were activated to counteract oxidative stress. Metallothioneins (MTs) were notably upregulated, contributing to arsenic detoxification. Transport proteins, including ABC transporters and ATP synthase beta subunits seems to play important roles in arsenic resistance. Additionally, proteins involved in protein degradation and redox balance, such as the RING finger protein and selenoprotein W1, supported the plant's adaptive response. These findings highlight the complex proteomic changes that enable T. foenum-graecum to tolerate arsenic stress and enhance its phytoremediation potential.