Imaging Mass Spectrometry of Specialized Metabolites in Plants

It is important to understand accumulation site of target secondary/specialized metabolites to identify genes regarding their biosynthesis in the integrated metabolomics because there are often correlations between accumulation of the metabolites and expression of the biosynthetic genes in plants. Imaging mass spectrometry (IMS) provides spatial information of phytochemicals on a section. Here, we developed a procedure of IMS analysis. Tissue slices (16 μm thickness) were prepared using cryostat CM3050S (Leica). The slices were immediately freeze-dried on slide glasses and were stored until use in room temperature. Matrices were sprayed to the slide glasses using the matrix sprayer ImagePrep (Bruker Daltonics). Ultrahigh resolution data (resolution power, 66,000 @ m/z 400) were acquired using the Fourier transform ion cyclotron resonance-mass spectrometry (FTICR-MS) instrument solariX 7.0 T (Bruker Daltonics) with a source of matrix assisted laser desorption ionization. Visualization of signal intensity on certain ions was performed using flexImaging (Bruker Daltonics). We successfully visualized the accumulation patterns of several specialized metabolites.