Exogenous melatonin mitigates cadmium toxicity through ascorbic acid and glutathione pathway in wheat

Area of Science:

• Plant Science
• Environmental Toxicology
• Biochemistry

Background:

• Cadmium (Cd) contamination in crops poses a significant human health risk via food chains.
• Melatonin (MT) is a plant growth regulator with potential to alleviate Cd toxicity, but its molecular mechanisms in wheat remain unclear.

Purpose of the Study:

• To elucidate the molecular mechanisms by which melatonin mitigates cadmium toxicity in wheat.
• To determine the optimal exogenous melatonin concentration for alleviating Cd stress in wheat.

Main Methods:

• Screening of exogenous melatonin concentration (50 μM) for mitigating Cd toxicity.
• Analysis of plant growth parameters, oxidative stress markers (MDA), and antioxidant levels (ASA, GSH).
• Quantitative analysis of gene expression for antioxidant enzymes (APX, GR, GST, DHAR, MDHAR) and Cd transporter genes (TaNramp1, TaNramp5, TaHMA2, TaHMA3, TaLCT1) in wheat roots.

Main Results:

• 50 μM melatonin significantly improved wheat growth and chlorophyll content while reducing malondialdehyde (MDA) levels under Cd stress.
• Melatonin treatment increased ascorbic acid (ASA) and glutathione (GSH) content, decreasing reactive oxygen species (ROS) and Cd accumulation in organelles.
• Expression of ASA-GSH synthesis genes (APX, GR, GST) increased, while some (DHAR, MDHAR) decreased under MT+Cd stress.
• Expression of Cd transporter genes (TaNramp1, TaNramp5, TaHMA2, TaHMA3, TaLCT1) was significantly downregulated by melatonin under Cd stress.

Conclusions:

• Melatonin alleviates cadmium toxicity in wheat by enhancing the ascorbic acid-glutathione antioxidant system.
• Melatonin suppresses the expression of key cadmium transporter genes, thereby regulating Cd uptake and translocation.
• The findings provide a molecular basis for using melatonin to improve crop quality and safety in Cd-contaminated environments.