抄録
Many plants in temperate regions enhance their freezing tolerance in winter. This phenomenon is known as
cold acclimation (CA). CA is controlled not only by low temperature but also by photoperiod via
phytochrome, a red/far-red photoreceptor. In Arabidopsis thaliana, phytochrome B (PHYB) is a key factor to
integrate photoperiod information into CA process. In the field, the daily temperature fluctuation is entrained
by a 24-h light-dark cycle. However, previous studies have not been focused on it. Here, we studied the
effect of photoperiod and daily temperature fluctuation on CA, focusing on the role of PHYB. Arabidopsis
wild type (WT) and phyB mutant were cold-acclimated for 7 days under 8-h or 12-h photoperiod, and then
freezing tests were performed. On CA at constant 2°C, the freezing tolerance of phyB was significantly lower
than that of WT only under 12-h photoperiod. On CA at 11°C light/2°C dark, the freezing tolerance of phyB
was significantly lower only under 8-h photoperiod. Our results suggest that the CA regulation mechanism
via PHYB differs with the temperature condition on CA.
