Lipidomics and spatial metabolomics reveal the heterogeneity in lipid distribution within pecan kernels

Pecan (Carya illinoinensis) is a globally important nut crop, yet the processes of lipid biosynthesis and spatial lipid distribution within its embryo remain poorly understood. This study employed UHPLC-MS/MS and MALDI-MSI to profile lipids in developing pecan embryos, identifying 401 lipid molecules, including a high abundance of glycerolipids (148) and glycerophospholipids (144). Differential diacylglycerols showed gradual uptrends, highlighting their role in synthesizing glycerolipids and glycerophospholipids. Unsaturated fatty acids, especially oleic, linoleic, and linolenic acids, were enriched in triacylglycerols, diacylglycerols, phosphatidylethanolamines, and phosphatidylcholines. MALDI-MSI revealed the spatial distribution of phosphatidic acid (PA), phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI), suggesting heterogeneous lipid distribution within embryos. The proportion of linoleic and linolenic acids is higher in the kernel coat, whereas the proportion of oleic acid is relatively higher in the cotyledons. Differences in lipid content were also observed between the inner and outer cotyledons. This study provides the first comprehensive map of lipid distribution in pecan embryos, offering new insights into lipid metabolism regulation.