The arabidopsis mutant lacking acyl-CoA-binding protein ACBP1 is freezing tolerant

Abstract

A family of six genes, designated ACbp1 to ACbp6, encodes Arabidopsis acyl-coenzyme A-binding proteins (ACBPs). ACBP1 contains an n-terminal transmembrane domain that targets it to the plasma membrane and the endoplasmic reticulum (ER), and C-terminal ankyrin repeats. To establish ACBP1 function, transgenic Arabidopsis plants overexpressing ACBP1 were subject to lipid analysis. ACBP1 overexpressors showed reduction in several species of diunsaturated phosphatidylcholine (PC), prompting us to examine if they were altered in response to freezing stress. Results revealed that ACBP1 overexpressors showed increased freezing sensitivity accompanied by a decrease in PC and an increase in phosphatidic acid (PA). In contrast, acbp1 mutant plants demonstrated an enhanced freezing tolerance associated with PC accumulation and PA reduction. Since phospholipase Dα1 is a major enzyme that promotes the hydrolysis of PC to PA, PLDα1 expression was investigated and was observed to be higher in ACBP1 overexpressors than acbp1 mutants. However, the expression of PLDδ, a positive regulator in freezing tolerance, had declined in ACBP1 overexpressors and increased in acbp1 mutants. Given that the ACBP1-mediated response is independent of osmolyte accumulation, ACBP1, which can bind phospholipids, could regulate the pool of membrane-associated phospholipids at the ER and plasma membrane