Citrate-Glutamate-Ca2+ Pathway Promoted Cd Sequestration in Rice Root Cell Walls

Area of Science:

• Agricultural Science
• Environmental Science
• Biochemistry

Background:

• Cadmium contamination in rice poses a significant threat to food safety and human health.
• Rice roots act as the primary barrier against cadmium (Cd) entry into the plant.
• Understanding mechanisms to mitigate Cd uptake is crucial for ensuring safe rice production.

Purpose of the Study:

• To investigate the role of citrate (CA) in inhibiting cadmium uptake and transport in rice roots.
• To elucidate the molecular mechanisms by which citrate affects cadmium accumulation in rice.
• To assess the impact of citrate application on reducing cadmium levels in rice grains and associated risks.

Main Methods:

• Conducted field and hydroponic experiments with rice under varying cadmium and citrate conditions.
• Quantified cadmium concentrations in rice seedlings and grains.
• Analyzed the citrate-glutamate-Ca2+ signaling pathway and its effect on cell wall components.

Main Results:

• Citrate application significantly reduced cadmium uptake and translocation in rice by 40.2-47.9% in seedlings and 36.0-54.6% in grains.
• Citrate enhanced the synthesis of glutamate (Glu), activating the citrate-glutamate-Ca2+ signaling pathway.
• This pathway led to increased synthesis of cell wall polysaccharides (cellulose, lignin, pectin) and reduced pectin methylation, strengthening the root barrier.

Conclusions:

• The citrate-glutamate-Ca2+ signaling pathway effectively immobilizes cadmium within rice root cell walls.
• This mechanism limits cadmium absorption and translocation, leading to safer rice grains.
• Citrate application presents a viable strategy to mitigate cadmium contamination in rice, reducing human health and ecological risks.