Cold-induced alterations in plasma membrane proteins that are specifically related to the development of freezing tolerance in cold-hardy winter wheat
1994
Zhou, B.L. | Arakawa, K. | Fujikawa, S. | Yoshida, S.
The objective of this study was to identify plasma membrane proteins that are specifically induced by cold acclimation in wheat (Triticum aestivum L.). Two cultivars with a marked difference in the genetic ability to cold-acclimate, namely, spring wheat (cv. Chinese Spring) and winter wheat (cv. Norstar), were used as the experimental material. After four weeks of growth in a cold chamber, the freezing tolerance in the shoots of winter wheat increased to -18 degrees C, whereas it increased only to -8 degrees C in the shoots of spring wheat. In the case of roots from both cultivars, freezing tolerance increased only slightly after the growth in the cold environment. Cold acclimation induced remarkable changes in the electrophoretic patterns of plasma membrane proteins which depended on both the cultivar and the tissue examined. Levels of polypeptides with molecular masses from 22 to 31 kDa decreased in both the root and shoot plasma membranes from both cultivars. Among these polypeptides, levels of those of 28 and 26 kDa decreased abruptly after one week of cold acclimation. By contrast, levels of polypeptides of 89, 83, 52, 23, 18 and 17 kDa increased specifically in the shoots of winter wheat. The increases in the levels of the 23-, 18- and 17-kDa polypeptides were proportional to the development of freezing tolerance. Freeze-fracture electron microscopy of plasma membranes from shoot cells revealed that the number of intramembrane particles on the fracture faces decreased markedly in winter wheat after cold acclimation, but to a lesser extent in spring wheat. These results suggest that the plasma membranes might undergo molecular reorganization during cold acclimation.
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