Minisymposium 24: Temperature Response

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Abs # M2402: Dynamic changes in the Arabidopsis plasma membrane associated with the process of cold acclimation

Presenter:	Uemura, Matsuo       Contact Presenter
Authors	Minami, Anzu  (A)   Shigematsu, Satomi  (B)   Furuto, Akari  (B)   Tominaga, Yoko  (B) (C)  Yamazaki, Tomokazu  (A)   Kawamura, Yukio  (A)   Uemura, Matsuo  (B) (A)
Affiliations:	(A): The 21st Century COE Program, Iwate University (B): Cryobiosystem Research Center, Iwate University (C): Departement des Sciences Biologiques, Universite du Quebec a Montreal

Many temperate plants increase freezing tolerance upon cold acclimation as a consequence of many diverse alterations in association with cold-regulated gene expression. These alterations ultimately result in an increase in the cryostability of the plasma membrane, the primary site of freezing injury in plants. With Arabidopsis thaliana, the plasma membrane alters dynamically both as a unit and in a specific protein during cold acclimation. Here we specifically report a possible involvement of (1) "microdomains" of the plasma membrane and (2) a plasma membrane-associated lipocalin-like protein (AtLCN) in the cold acclimation process. The microdomain fractions of the plasma membrane of Arabidopsis leaves were technically isolated as detergent resistant membrane (DRM) fraction from purified plasma membrane with Triton X-100 at 4^oC. Immunofluorescence microscopy with an antibody of plasma membrane H⁺-ATPase, a plant DRM marker protein, revealed that localization of the protein was not uniform in the plasma membrane sheet prepared from a protoplast isolated from Arabidopsis leaves. In addition, several proteins were apparently enriched in the DRM fraction. These results strongly suggest the existence of microdomains with specific compositions in the plant plasma membrane. The recovery of DRM fraction from the plasma membrane on protein basis decreased gradually during cold acclimation, suggesting a close association of DRM with the content of the primary DRM-associated lipids, glucocerebrosides, which has been reported to decrease during cold acclimation in Arabidopsis. In addition, protein expression analysis with 1D- and 2D-SDS-PAGE revealed that there are quantitative changes in DRM-associated proteins during cold acclimation. Furthermore, overexpression of AtLCN, a non DRM-associated protein, resulted in a significant increase in freezing tolerance of whole plants, detached leaves and isolated protoplasts. AtLCN were eventually found to be physically associated with several classes of plasma membrane phospholipids, which may result in the stabilization of the plasma membrane under freezing conditions and, hence, increase in freezing tolerance of Arabidopsis after cold acclimation. These results taken together suggest that cold-induced alterations in the plant plasma membrane occur through complex pathways with a proper coordination. Supported partly by grants from the MEXT, Japan (the 21st Century COE Program K-03 and Scientific Research Grant #17380062).