Abstract
Plant freezing tolerance is one of the most important factors which determine the productivity and distribution in the world. Temperate plants including many crop species have an ability to increase their freezing tolerance when exposed to low but non-freezing temperatures for certain periods, which is known as cold acclimation. Cold-acclimation-induced increase in freezing tolerance is associated with diverse changes occurring in the plasma membrane, which ultimately results in an increase in the cryostability of the plasma membrane to withstand various abiotic stresses imposed by freezing (i.e., dehydration, high-salt, and mechanical stresses) and an acceleration of the recovery process after thawing. We have intensively investigated alterations in the plasma membrane composition and accumulated evidences that indicate dynamic responses of protein and lipid compositions in the plasma membrane to low temperatures. Recently, we have initiated analysis of microdomains in the plasma membrane during cold acclimation and found that both the protein and lipid compositions of the microdomains significantly altered after cold acclimation. A microdomain-localized protein, synaptotagmin-like protein 1 (SYT1), which becomes concentrated in microdomains after cold acclimation, is likely to functionally involve in calcium-associated membrane repair process that is essential to maintain high survival after a freeze/thaw cycle. These results confirm that plant plasma membrane is the most important factor to determine how plant cells tolerate freezing conditions.
