SE151:/DS1

Sample Set Information

ID	TSE1306
Title	Plant lipidomics based on hydrophilic interaction chromatography coupled to ion trap time-of-flight mass spectrometry.
Description	Plants synthesize a wide range of hydrophobic compounds, generally known as lipids. Here, we report an application of liquid chromatography ion trap time-of-flight mass spectrometry (LC-IT-TOF-MS) for plant lipidomics. Using hydrophilic interaction chromatography (HILIC) for class separation, typical membrane lipids including glycerolipids, steryl glucosides and glucosylceramides, and hydrophobic plant secondary metabolites such as saponins were analyzed simultaneously. By this method, we annotated approximately 100 molecules from Arabidopsis thaliana. To demonstrate the application of this method to biological study, we analyzed Arabidopsis mutant trigalactosyldiacylglycerol3 (tgd3), which has a complex metabolic phenotype including the accumulation of unusual forms of galactolipids. Lipid profiling by LC-MS revealed that tgd3 accumulated an unusual form of digalactosyldiacylglycerol, annotated as Gal(β1 → 6)βGalDG. The compositional difference between normal and unusual forms of digalactosyldiacylglycerol was detected by this method. In addition, we analyzed well-known Arabidopsis mutants ats1-1, fad6-1, and fad7-2, which are also disrupted in lipid metabolic genes. Untargeted lipidome analysis coupled with multivariate analysis clearly discriminated the mutants and their distinctive metabolites. These results indicated that HILIC-MS is an efficient method for plant lipidomics.
Authors	Okazaki Y, Kamide Y, Hirai MY, Saito K.
Reference	Metabolomics. 2013 Mar;9(Suppl 1):121-131. Epub 2011 May 31.
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PubMed

Data Analysis Details Information

ID	DS1
Title	Data processing
Description	Peak picking and peak alignment were performed by Profiling Solution (version 1.0.76.0) (Shimadzu Corporation, Kyoto, Japan). The Profiling Solution parameters were as follows: ion m/z tolerance, 20 mDa; Ion RT tolerance, 0.1 min; Ion intensity threshold, 2e4; detect isomer valley, 20%; allow some ion without isotope peak, ON; time range for processing, 0–20 min. The data matrix containing 534 ions was exported from Profiling Solution and normalized based on the intensity of [M + HCO2]− of 10:0/10:0 PC. Peak height of individual galactolipid molecules were calculated based on the m/z values of [M + HCO2]−. Because lipid species with the same polar head eluted at almost the same retention time, corrections for overlap of isotopic variants in higher-mass lipids were applied. Annotation was based on theoretical m/z values of each possible glycerolipid species in plants and retention time of authentic compounds with same polar head using an in-house Perl script. After this process, data was pareto-scaled and subjected to PCA and OPLS-DA using SIMCA-P (version 11.0.0.0, Umetrics, Umeä, Sweden).
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