Abstract
Freezing tolerance is one of the most important characteristics for plants living at subzero temperatures in winter. When ice crystals form and grow in the extracellular spaces they may bring cells, especially cell surface, to the dehydration and mechanical stresses. Many physiological studies have supported the hypothesis that the enhancement of freezing tolerance in plants during cold acclimation is closely associated with an increase in the cryostability of plasma membrane. In Arabidopsis, many of the plasma membrane proteins including dehydrins, lipocalin and synaptotagmin increase during cold acclimation. Although there was little information about the freeze-induced mechanical stress tolerance, we have revealed that the extracellular calcium increases the tolerance to freeze-induced mechanical stress, the mechanism of which is involved in the membrane resealing via plant synaptotagmin, SYT1. Recently, besides Arabidopsis, we confirmed the calcium-dependent freezing tolerance in three monocot and one dicot. In addition, freezing tolerance tests of three monocots in the presence of anti-SYT1 antibody demonstrated that the calcium-dependent freezing tolerance results in the membrane repair. Finally, our results support the idea that the calcium-dependent membrane repair is a common mechanism of freeze-induced mechanical stress tolerances for many angiosperms.
