Mechanisms of Freezing Stress Tolerance in Plants

Low temperature constrains plant growth and restricts productivity in temperate regions.
Plants use two different adaptation strategies to withstand or survive cold temperatures freezing avoidance and freezing tolerance.
Supercooling process is a prevalent mechanism of freeze avoidance in which water remains in the liquid state at sub-zero temperature, preventing intracellular freezing and limiting cell dehydration.
Freezing tolerance, instead, affect physiological, biochemical, and epigenetic changes that allow to the plant response to cold stress.
The most popular approach used by plants to deal with low temperature stress is cold acclimation, which allows plants to survive freezing via accumulation of cryoprotective polypeptides (e.g., COR15a) and osmolytes (e.g., soluble sugars and proline).
ICE is a CBF regulator, and CBFs control the expression of the COR gene when cold stress takes place.
The COR gene is a critical gene that is responsible for chilling tolerance and cold acclimation processes in plants.
Under normal conditions, CBFs are regulated by the circadian clock and the photoperiod.
Under cold stress conditions, however, CBFs induce several cold stress-related genes to regulate the cold tolerance of plants.
The expression of CBFs is mainly mediated by DELLA signaling and induced by ICE1.
ICE is a pioneer of cold acclimation, an MYC-type basic helix-loop-helix family transcription factor.
DELLAs contribute to the cold induction of CBF genes through interaction with JaZs signaling.
CBFs activate the expression of COR genes via binding to cis-elements in the promoter of COR genes and
result in the enhancement of cold tolerance in plants.
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