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Media type:
E-Article
Title:
Lamellar-to-hexagonalIIPhase Transitions in the Plasma Membrane of Isolated Protoplasts after Freeze-Induced Dehydration
Contributor:
Gordon-Kamm, William J.;
Steponkus, Peter L.
Published:
National Academy of Sciences of the United States of America, 1984
Published in:
Proceedings of the National Academy of Sciences of the United States of America, 81 (1984) 20, Seite 6373-6377
Language:
English
ISSN:
0027-8424
Origination:
Footnote:
Description:
In protoplasts isolated from nonacclimated rye leaves (Secale cereale L. cultivar Puma), cooling to -10 degrees C at a rate of 1 degrees C/min results in extensive freeze-induced dehydration (osmotic contraction), and injury is manifested as the loss of osmotic responsiveness during warming. Under these conditions, several changes were observed in the freeze-fracture morphology of the plasma membrane. These included (i) lateral phase separations in the plasma membrane, (ii) aparticulate lamellae lying next to the plasma membrane, and (iii) regions of the plasma membrane and associated lamellae in various stages of lamellar-to-hexagonalIItransition. These morphological changes also were observed after equilibration in 5.37 osmolal sorbitol at 0 degrees C, which produced a similar extent of dehydration as did freezing to -10 degrees C. In contrast, only small areas of lateral phase separation in the plasma membrane, with no observable aparticulate lamellae or hexagonalIIconfigurations, were observed in protoplasts supercooled to -10 degrees C. Therefore, freeze-induced lamellar-to-hexagonalIIphase transitions in the plasma membrane are a consequence of dehydration rather than subzero temperature per se. When suspensions of protoplasts isolated from cold-acclimated leaves were frozen to -10 degrees C, no injury was incurred, and hexagonalIIphase transitions were not observed. No hexagonalIIphase was observed even at -35 degrees C, though acclimated protoplasts are injured at this temperature.