Lipidomic analysis of N-acylphosphatidylethanolamine molecular species in Arabidopsis suggests feedback regulation by N-acylethanolamines
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N-Acylphosphatidylethanolamine (NAPE) and its hydrolysis product, N-acylethanolamine (NAE), are minor but ubiquitous lipids in multicellular eukaryotes. Various physiological processes are severely affected by altering the expression of fatty acid amide hydrolase (FAAH), an NAE-hydrolyzing enzyme. To determine the effect of altered FAAH activity on NAPE molecular species composition, NAE metabolism, and general membrane lipid metabolism, quantitative profiles of NAPEs, NAEs, galactolipids, and major and minor phospholipids for FAAH mutants of Arabidopsis were determined. The NAPE molecular species content was dramatically affected by reduced FAAH activity and elevated NAE content in faah knockouts, increasing by as much as 36-fold, far more than the NAE content, suggesting negative feedback regulation of phospholipase D-mediated NAPE hydrolysis by NAE. The N-acyl composition of NAPE remained similar to that of NAE, suggesting that the NAPE precursor pool largely determines NAE composition. Exogenous NAE 12:0 treatment elevated endogenous polyunsaturated NAE and NAPE levels in seedlings; NAE levels were increased more in faah knockouts than in wild-type or FAAH overexpressors. Treated seedlings with elevated NAE and NAPE levels showed impaired growth and reduced galactolipid synthesis by the “prokaryotic” (i.e., plastidic), but not the “eukaryotic” (i.e., extraplastidic), pathway. Overall, our data provide new insights into the regulation of NAPE–NAE metabolism and coordination of membrane lipid metabolism and seedling development.
KeywordsMass spectrometry Lipidomics Lauroylethanolamide Phospholipid
Fatty acid amide hydrolase
Free fatty acid
Solid phase extraction
Designates fatty acid or total acyl carbons:total carbon–carbon double bonds
This work was supported by a grant from the United States Department of Energy, Office of Basic Energy Sciences (BES, grant number DE-FG02-05ER15647) and a seed grant from the University of North Texas to KDC. Method development and equipment acquisition at the Kansas Lipidomics Research Center was funded by National Science Foundation (DBI 0521587; MCB 0455318 and 0920663), Kansas IDeA Networks of Biomedical Research Excellence (INBRE) of the National Institute of Health (P20RR16475) and Kansas State University.
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