Mass spectrometry imaging (MSI) is a developing technique to measure the spatio-temporal distribution of many biomolecules in tissues. Over the preceding decade, MSI has been adopted by plant biologists and applied in a broad range of areas, including primary metabolism, natural products, plant defense, plant responses to abiotic and biotic stress, plant lipids and the developing field of spatial metabolomics. This review covers recent advances in plant-based MSI, general aspects of instrumentation, analytical approaches, sample preparation and the current trends in respective plant research.

Metabolites, lipids, and other small molecules are key constituents of tissues supporting cellular programs in health and disease. Here, we present METASPACE, a community-populated knowledge base of spatial metabolomes from imaging mass spectrometry data. METASPACE is enabled by a high-performance engine for metabolite annotation in a confidence-controlled way that makes results comparable between experiments and laboratories. By sharing their results publicly, engine users continuously populate a knowledge base of annotated spatial metabolomes in tissues currently including over 3000 datasets from human cancer cohorts, whole-body sections of animal models, and various organs. The spatial metabolomes can be visualized, explored and shared using a web app as well as accessed programmatically for large-scale analysis. By using novel computational methods inspired by natural language processing, we illustrate that METASPACE provides molecular coverage beyond the capacity of any individual laboratory and opens avenues towards comprehensive metabolite atlases on the levels of tissues and organs.

Mass spectrometry imaging (MSI) is a developing technique to measure the spatiotemporal distribution of many biomolecules in tissues. Over the preceding decade MSI has been adopted by plant biologists and applied in a broad range of areas including: primary metabolism, natural products, plant defense, plant responses to abiotic and biotic stress, plant lipids, and the developing field of spatial metabolomics. This methods chapter covers preparation of plant tissues for matrix-assisted laser desorption ionization (MALDI)-MSI, including sample embedding and freezing, sectioning, mounting, and matrix deposition using both sublimation and spray deposition prior to MSI analysis.

A covalent, robust, nano-sized tetrahedral cage containing six silicon centres has been synthesised and structurally characterised.