Effect of COR proteins on the freeze-induced fusion of liposomes

Conference · Sat May 01 04:00:00 UTC 1993 · Plant Physiology; (United States)

OSTI ID:6282059

Uemura, M; Steponkus, P L ^[1]; Gilmour, S J; Thomashow, M F ^[2]

---

1. Cornell Univ., Ithaca, NY (United States)
2. Michigan State Univ., East Lansing (United States)

Although substantial progress has been made in identifying genes that are regulated during cold acclimation, with few exceptions, the function of the COR proteins encoded by these genes is not known. The objectives of this study were to determine if COR6.6 and COR15am, which are synthesized in Arabidopsis thaliana, influence the freeze-induced fusion of lipid bilayers. When small unilamellar vesicles (SUVs) composed of either POPC (16:0/18:1) or DOPC (18:1/18:1) were frozen to temperatures over the range of [minus]2[degrees]C to [minus]30[degrees]C liposome fusion occurred at temperatures below [minus]2[degrees]C, with a substantial increase occurring at temperatures below the T[sub m] of the lipids ([minus]3[degrees]C for POPC and [minus]18[degrees]C for DOPC). Freeze-induced fusion was not observed SUVs composed of BL[sub 2]PC (18:2/18:2), which has a t[sub m] of [minus]55[degrees]C. Addition of either COR6.6 or COR15am significantly decreased the incidence of fusion of large unilamellar vesicles of DOPC if proteins were added to the liposome suspension before freezing; there was no effect if the COR proteins were only encapsulated within the liposomes. With SUVs formed from the total lipid extract of the plasma membrane of either non-acclimated (NA) or cold-acclimated (ACC) rye leave, there was differential response to freezing. In NA-SUVs, the incidence of fusion increased after freezing to [minus]5[degrees]C and reached a maximum at [minus]10[degrees]C; in ACC-SUVs, the maximum incidence of fusion occurred at [minus]20[degrees]C. The difference in cryostability reflects differences in the lipid composition of the plasma membrane after cold acclimation. But there was a significant decrease in the incidence of fusion in both NA- and ACC-SUVs when frozen in the presence of either COR6.6 or COR15am. Thus, although the cryostability of lipid bilayers is primarily influenced by the lipid composition of the bilayers, there is an additive effect of the COR proteins.

• DOE Contract Number: FG02-84ER13214
• OSTI ID: 6282059
• Report Number(s): CONF-9307119--
• Conference Information: Journal Name: Plant Physiology; (United States) Journal Volume: 102:1
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
550300* -- Cytology
59 BASIC BIOLOGICAL SCIENCES
ARABIDOPSIS
BIOLOGICAL ADAPTATION
BIOLOGICAL EFFECTS
BIOLOGICAL FUNCTIONS
CEREALS
FREEZING
GENES
GRAMINEAE
LILIOPSIDA
LIPIDS
LIPOSOMES
MAGNOLIOPHYTA
MAGNOLIOPSIDA
MEMBRANES
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
PLANT CELLS
PLANTS
PROTEINS
RYE