Abstract
During non-freezing temperature, many plants have to enhance cold and freezing tolerance to survive in
winter. This phenomenon is called as a cold acclimation. It has been widely accepted that calcium ion (Ca2+)
may act as a second messenger in the cold acclimation process, because low temperature and/or cold shock
induce the rapid increase in cytosolic Ca2+ concentration. However, its role in cold acclimation is still
unknown. We established the experimental system to observe Ca2+ signals with the combination of a confocal
cryomicroscope and transgenic Arabidopsis expressing FRET-based Ca2+ sensor Yellow Cameleon 3.60.
Because the dispersion in Ca2+ signal was observed among samples, a moving average method was employed
after averaging data to seek the peak of the Ca2+ signal. The moving average method revealed that a distinct
increase in Ca2+ concentration hardly arise until the temperature decrease of more than 3°C, indicating that a
certain level of temperature change may be needed to induce a specific Ca2+ signal. Ca2+ signals would be a
clue to how plants sense low- temperature.
