Measurement of Net NH₄ ⁺ Fluxes Using the Non-invasive Micro-Test Technology (NMT) System in Rice

Area of Science:

• Plant Physiology
• Molecular Biology
• Biochemistry

Background:

• Ammonium (NH4+) is a crucial nitrogen source for rice (Oryza sativa L.).
• Subcellular ammonium dynamics, especially vacuolar sequestration and efflux, are poorly understood due to detection limitations.
• Existing methods struggle with organellar-scale measurements and ion adsorption in root cell walls.

Purpose of the Study:

• To present a reproducible protocol for real-time measurement of net NH4+ fluxes in rice.
• To enable quantification of NH4+ transport at multiple biological levels: intact roots, protoplasts, and isolated vacuoles.
• To facilitate a deeper understanding of NH4+ homeostasis and nitrogen transport mechanisms in plants.

Main Methods:

• Utilized non-invasive micro-test technology (NMT) for real-time flux measurements.
• Developed a protocol for preparing rice root protoplasts and isolated vacuoles.
• Applied a unified strategy for sample preparation and NMT measurement across different biological scales.

Main Results:

• Successfully quantified net NH4+ uptake fluxes across the plasma membrane.
• Characterized net NH4+ efflux dynamics under various conditions.
• Enabled indirect estimation of vacuolar NH4+ sequestration capacity.

Conclusions:

• The NMT-based protocol offers a robust framework for studying NH4+ homeostasis in plants.
• The protocol is adaptable to different plant species, culture systems, and experimental conditions.
• This method overcomes previous limitations, paving the way for advanced research in plant nitrogen transport.