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Investigation of optimal sample preparation method for mass spectrometry imaging of endogenous metabolites in Arabidopsis
Plants accumulate numerous primary and secondary metabolites to survive under various stress conditions. Spatiotemporal information of their metabolites within tissue is indispensable for elucidating the precise mechanisms of physiological regulation and/or function of biomolecules in plants. Matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry imaging (MSI) enables determination of the distribution of ionizable molecules exist in tissue surface at high-spatial resolution. We already developed in situ metabolomic imaging technique using animal tissue section (Miura et al. Anal. Chem. (2010) 82, 9789). In this study, we investigated the optimal sample preparation procedure for MSI experiment using Arabidopsis leaf. Previously, the sublimation is reported to be suitable method for matrix application to detect glucosinolates from plant leaf. By the optimization of matrix and the modification of matrix application method (sublimation coupled with recrystallization), we succeeded to improve detection sensitivity and spatial resolution in MSI. Additionally, we attempted to remove off epidermis and mesophyll from the surface layer of leaf. As the result, we succeeded to detect unique metabolites existing in the internal structure of the leaf by removal of the epidermis. Then we demonstrated the newly optimized methodology of MALDI-MSI for plant tissue enables to visualize the distribution of global endogenous metabolites in Arabidopsis.