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Overexpression of the Arabidopsis 10-kilodalton acyl-coenzyme A-binding protein ACBP6 enhances freezing tolerance.

Authors
  • Chen, Qin-Fang
  • Xiao, Shi
  • Chye, Mee-Len
Type
Published Article
Journal
PLANT PHYSIOLOGY
Publisher
American Society of Plant Biologists
Publication Date
Sep 01, 2008
Volume
148
Issue
1
Pages
304–315
Identifiers
DOI: 10.1104/pp.108.123331
PMID: 18621979
Source
Medline
License
Unknown

Abstract

Small 10-kD acyl-coenzyme A-binding proteins (ACBPs) are highly conserved proteins that are prevalent in eukaryotes. In Arabidopsis (Arabidopsis thaliana), other than the 10-kD ACBP homolog (designated Arabidopsis ACBP6), there are five larger forms of ACBPs ranging from 37.5 to 73.1 kD. In this study, the cytosolic subcellular localization of Arabidopsis ACBP6 was confirmed by analyses of transgenic Arabidopsis expressing autofluorescence-tagged ACBP6 and western-blot analysis of subcellular fractions using ACBP6-specific antibodies. The expression of Arabidopsis ACBP6 was noticeably induced at 48 h after 4 degrees C treatment by northern-blot analysis and western-blot analysis. Furthermore, an acbp6 T-DNA insertional mutant that lacked ACBP6 mRNA and protein displayed increased sensitivity to freezing temperature (-8 degrees C), while ACBP6-overexpressing transgenic Arabidopsis plants were conferred enhanced freezing tolerance. Northern-blot analysis indicated that ACBP6-associated freezing tolerance was not dependent on the induction of cold-regulated COLD-RESPONSIVE gene expression. Instead, ACBP6 overexpressors showed increased expression of mRNA encoding phospholipase Ddelta. Lipid profiling analyses of rosettes from cold-acclimated, freezing-treated (-8 degrees C) transgenic Arabidopsis plants overexpressing ACBP6 showed a decline in phosphatidylcholine (-36% and -46%) and an elevation of phosphatidic acid (73% and 67%) in comparison with wild-type plants. From our comparison, the gain in freezing tolerance in ACBP6 overexpressors that was accompanied by decreases in phosphatidylcholine and an accumulation of phosphatidic acid is consistent with previous findings on phospholipase Ddelta-overexpressing transgenic Arabidopsis. In vitro filter-binding assays indicating that histidine-tagged ACBP6 binds phosphatidylcholine, but not phosphatidic acid or lysophosphatidylcholine, further imply a role for ACBP6 in phospholipid metabolism in Arabidopsis, including the possibility of ACBP6 in the cytosolic trafficking of phosphatidylcholine.

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