Tissue-resolved proteomic characterization of oat grains guided by metabolite MALDI mass spectrometry imaging

The metabolic architecture of oat grains remains poorly understood at the cellular and proteome levels despite increasing interest for applications such as nutritional enhancement and functional crop improvement. In this study, we performed matrix-assisted laser desorption and ionization mass spectrometry imaging (MALDI-MSI) to map metabolite distributions across oat grain tissues and delineate major compartments of metabolite localization. These metabolite-rich regions, notably the bran, endosperm, and embryo, were then isolated for proteomic analysis, which detected around 3700 proteins across all tissue types. Gene ontology analysis highlighted specialized functions and biological processes associated with each compartment. Further interrogation of key proteins revealed the enrichment of core cellular functions such as energy generation, translation, and stress resilience in the embryo, nutrient storage in the endosperm, and an intermediate functional profile in the bran. These findings provide new insights into the spatial organization of metabolic functions within oat grains and warrant further exploration of sub-regions for a deeper understanding of the oat metabolic architecture.