Mass Spectrometry Imaging of Metabolites in Barley Grain Tissues

Higher plants are composed of a multitude of tissues with particular functions, reflected by distinct profiles of transcripts, proteins, and metabolites. Although the rapid development of "omics" technologies has advanced plant science tremendously within recent years, analysis is frequently performed on whole organ or whole plant extracts, causing the loss of spatial information. Mass spectrometry-based imaging (MSI) approaches have become a powerful tool to decipher spatially resolved molecular information. Matrix-assisted laser desorption/ionization (MALDI) is the most widespread ionization method utilized for MSI and has recently been applied to plant science. A range of different plant organs and tissues has been successfully analyzed by MSI, and patterns of various classes of metabolites from primary and secondary metabolism have been obtained. This protocol describes a method for analysis of spatial metabolite distributions in cryosections of developing barley grains. Detailed procedures for sample preparation, mass spectrometry measurement, and data analysis are provided. © 2016 by John Wiley & Sons, Inc.