Figure 2.

A comprehensive schematic summary of cryoprotectants mechanism of action and cold stress modulation in plants. Cryoprotectants regulate osmolytes such as proline, glycol, glycerol and ANE. The increased accumulation of these osmolytes triggers the induction of cold regulating (COR) genes through the activation of transcriptional activators called C-repeat Binding Factors (CBFs), which are involved in reducing cell dehydration, regulating membrane proteins and synthesizing antifreeze proteins (AFPs). Sugar molecules also participate in this regulation by reducing cell dehydration and modulating membrane proteins, including antifreeze proteins (AFPs). AFPs are secreted into extracellular spaces, attaching to ice crystals to prevent ice aggregation, resulting in suppressing recrystallization and reducing cell dehydration. Additionally, cryoprotectants trigger K⁺ interacting with Ca²⁺ that plays an important role in the hydrodynamic stomatal closure mechanism, leading to reduced cell dehydration. Furthermore, cryoprotectants establish hydrogen bonds with intracellular water molecules, restricting their movement into extracellular spaces and inhibiting its conversion into ice crystals. This hydrogen bonding lowers the freezing point of water. In addition, certain cryoprotectants scavenge ROS either through their antioxidant properties or through its osmoregulatory properties that contributes to maintaining cellular osmotic balance and integrity by regulating water movement across the membrane, resulting in enhanced plasma membrane stability. Collectively, these mechanisms prevent the formation of ice-nucleation sites on the membrane surface, which is a critical step in the initiation of extracellular ice crystal formation and subsequent freezing stress. Arrows indicate positive regulation while dashed line with a perpendicular line at the end indicates negative regulation. ROS, reactive oxygen species; CBF, C-repeat Binding Factors, COR, cold-responsive, AFP, antifreeze proteins, ANE, Ascophyllum nodosum (Seaweed) extract.