Abstract
In a previous report, synaptotagmin-like protein, a membrane repair-related protein, which quickly increased during cold acclimation was identified in the Arabidopsis plasma membrane fraction (Kawamura and Uemura 2003). Rapid membrane repair is a general phenomenon in animal cells although no report has been published on this mechanism in plant cells. The mechanical disruption of plasma membrane results in the incursion of extracellular calcium into cytoplasm, and consequently, endomembranes fuse into the damaged plasma membrane through the exocytosis in which SNAREs and synaptotagmin family are involved. When the plasma membrane is mechanically disrupted by the ice formation and/or by the freeze-induced dehydration, it is possible that the plant cells rapidly repair the disruption dependently on the extracellular calcium. In our results, the freezing tolerances of Arabidopsis protoplasts isolated from control and cold-acclimated leaves remarkably decreased when survival tests were carried out in the buffer without calcium. (Supported by JSPS Research Fellowships)
