CBL1/9-CIPK23-NRAMP1 axis regulates manganese toxicity

Area of Science:

• Plant Biology
• Molecular Plant Physiology
• Environmental Plant Science

Background:

• Manganese (Mn) is essential but toxic at high concentrations, especially in acidic soils affecting 30% of Earth's land.
• Understanding Mn uptake and toxicity mechanisms is crucial for crop yield and plant health.

Purpose of the Study:

• To elucidate the molecular mechanisms regulating plant tolerance to manganese toxicity.
• To identify key genetic components involved in manganese homeostasis in plants.

Main Methods:

• Reverse genetics to identify high-Mn sensitive mutants (cbl1/9, cipk23).
• Protein interaction techniques and kinase assays to investigate CIPK23 and NRAMP1 interaction.
• In vitro and in vivo experiments to analyze NRAMP1 phosphorylation and endocytosis.

Main Results:

• CBL1/9 and CIPK23 positively regulate Mn toxicity tolerance in Arabidopsis.
• Mutants cbl1/9 and cipk23 show hypersensitivity to Mn, with reduced growth and chlorophyll, and increased Mn accumulation.
• CIPK23 phosphorylates the Mn transporter NRAMP1, inducing its clathrin-mediated endocytosis and reducing plasma membrane abundance.

Conclusions:

• The CBL1/9-CIPK23-NRAMP1 module is a key regulator of plant tolerance to high manganese levels.
• Phosphorylation of NRAMP1 by CIPK23 is a critical step in managing Mn uptake and toxicity in plants.