CHANGES IN FREEZING TOLERANCE AND PROTEIN CONSTITUENTS OF LONICERA CAERULEA DURING COLD ACCLIMATION
Lonicera caerulea var. emphyllocalyx is an edible honeysuckle and a deciduous shrub native to the northern areas of Japan. In this study, we evaluated the freezing tolerance of twigs, based on the bud sproutings, collected from October to March from five different habitats in Hokkaido, Japan, and of calli. Differences in the freezing tolerance of twigs were recorded in February, and may possibly be ascribed to differences in air temperature and the depth of snow in the study areas. As evaluated by the 2,3,5-triphenyltetrazolium chloride (TTC) reduction test, the time needed to develop freezing tolerance began earlier and lasted longer in buds than in stems. Remarkably, there were no differences in freezing tolerance between buds and stems from December to January, when both tissue types showed a high freezing tolerance. During the period of decreasing freezing tolerance from winter to spring, buds showed greater tolerance than stems. Calli exposed to the low temperature of 5 °C increased their cold tolerance after 8 days of treatment, reaching a plateau on day 12; however, cold-treated calli lost their freezing tolerance within only 2 days of incubation at 25 °C. The proteins extracted from these calli were analyzed by two-dimensional polyacrylamide gel electrophoresis. Our results showed abundant accumulations of a 42 kDa (pI 5.4) protein during cold acclimation. This protein decreased during incubation at 25 °C. Manipulating the level of the 42 kDa (pI 5.4) protein through breeding may help to develop higher freezing tolerance in Lonicera caerulea var. emphyllocalyx.
Imanishi, H., Takada, K., Masuda, K., Suzuki, T. and Harada, T. (2003). CHANGES IN FREEZING TOLERANCE AND PROTEIN CONSTITUENTS OF LONICERA CAERULEA DURING COLD ACCLIMATION. Acta Hortic. 626, 445-450
edible honeysuckle, bud sprouting, TTC reduction, callus, two-dimensional polyacrylamide gel electrophoresis