Mode of action of the COR15a gene on the freezing tolerance of Arabidopsis thaliana.
Constitutive expression of the cold-regulated COR15a gene of Arabidopsis thaliana results in a significant increase in the survival of isolated protoplasts frozen over the range of -4.5 to -7 degreesC. The increased freezing tolerance is the result of a decreased incidence of freeze-induced lamellar-to-hexagonal II phase transitions that occur in regions where the plasma membrane is brought into close apposition with the chloroplast envelope as a result of freeze-induced dehydration. Moreover, the mature polypeptide encoded by this gene, COR15am, increases the lamellar-to-hexagonal II phase transition temperature of dioleoylphosphatidylethanolamine and promotes formation of the lamellar phase in a lipid mixture composed of the major lipid species that comprise the chloroplast envelope. We propose that COR15am, which is located in the chloroplast stroma, defers freeze-induced formation of the hexagonal II phase to lower temperatures (lower hydrations) by altering the intrinsic curvature of the inner membrane of the chloroplast envelope.
Steponkus
P L
PL
Department of Soil, Crop and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA. pls4@cornell.edu
Uemura
M
M
Joseph
R A
RA
Gilmour
S J
SJ
Thomashow
M F
MF
D000064:Acclimatization / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins; D003890:Desiccation; D005615:Freezing; D018506:Gene Expression Regulation, Plant; D009682:Magnetic Resonance Spectroscopy; D010714:Phosphatidylethanolamines / Q000737:chemistry; D018515:Plant Leaves; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology; D011523:Protoplasts / Q000502:physiology / Q000648:ultrastructure; D013816:Thermodynamics
D029681:Arabidopsis Proteins; C116166:COR15 protein, Arabidopsis; D010714:Phosphatidylethanolamines; D010940:Plant Proteins; C094877:dioleoyl phosphatidylethanolamine