Ca2+/MtCML39-MtMYB6 module regulates MtCBF1 expression and cold tolerance in Medicago truncatula
Risheng Huang1,2, Bohao Geng1, Qiaoqi Li1
1College of Grassland Science, Nanjing Agricultural University, No. 1 Weigang Road, Xuanwu District, Nanjing, Jiangsu 210095, China.
Plant Physiology
|July 10, 2026
Summary
Calcium signaling, via calmodulin-like protein MtCML39, regulates plant cold tolerance by interacting with MtMYB6. This interaction relieves repression on MtCBF1, activating the cold response pathway for enhanced freezing tolerance.
Area of Science:
- Plant Molecular Biology
- Plant Physiology
- Environmental Stress Response
Background:
- Calcium (Ca2+) acts as a crucial second messenger in plant stress responses.
- The C-repeat Binding Factor (CBF) pathway is vital for plant cold tolerance.
- The molecular link between Ca2+ signaling and the CBF pathway in cold response remains unclear.
Purpose of the Study:
- To investigate the molecular mechanism connecting Ca2+ signaling to the CBF pathway for cold tolerance.
- To identify key regulatory proteins involved in this signaling cascade.
- To elucidate the role of MtMYB6 and MtCML39 in cold acclimation.
Main Methods:
- Yeast two-hybrid assays to identify protein interactions.
- Electrophoretic mobility shift assays (EMSA) to study transcription factor binding.
- Gene expression analysis (RT-qPCR) to quantify transcript levels.
- Genetic manipulation (overexpression and gene editing) in Medicago truncatula.
- Physiological measurements of cold tolerance.
Main Results:
- MtMYB6 negatively regulates cold tolerance by repressing MtCBF1 expression.
- MtCML39, a Ca2+-dependent calmodulin-like protein, upregulates cold tolerance.
- Ca2+/MtCML39 disrupts MtMYB6 binding to the MtCBF1 promoter, relieving repression.
- MtMYB6 acts downstream of MtCML39, and Ca2+ is essential for the observed cold tolerance.
Conclusions:
- A novel signaling module involving Ca2+/MtCML39 and MtMYB6 regulates cold tolerance.
- Ca2+/MtCML39 relieves MtMYB6-mediated repression of MtCBF1, activating downstream cold-responsive genes.
- This pathway enhances freezing tolerance in plants under cold stress.
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