Abstract
Although elucidation of molecular mechanisms of cold acclimation in Arabidopsis plants is rapidly progressing, it is still difficult in some cases to determine responses to low temperatures at cellular levels due to the complexity of plant individuals. To study such responses, we characterized kinetics of cold acclimation with Arabidopsis T87 suspension cultured cells and compared the results with those obtained with seedlings. Acclimation-induced increase in freezing tolerance was detected with the cultured cells only at late lag phase at a narrow time-window (1-2 days) of cold acclimation. Expression of cold-regulated genes (DREB1A, RD29A, and COR15a) increased rapidly after acclimation (6-24 hr) but suddenly decreased thereafter. We also found that an increase in sucrose concentration in cultured medium extended the time-window for cold acclimation. These results suggest that kinetics of cold acclimation are different between seedlings and cultured cells and are influenced by sugars in the cultured medium.
