Lipids modifications during walnut development: Changes in the composition and metabolic regulation of oil bodies

•Lipidomics were conducted on WOBs during walnut development for the first time.•A total of 305 kinds of lipids were identified.•Some lipids had rich molecular numbers and dynamic changes with walnut development.•DALs were selected out and could be used as markers for the growth stage of walnut.•Linoleic acid metabolism was the most important metabolic pathway of lipid metabolism in WOBs. Walnut oil bodies (WOBs), the storage lipid organelles that forms and accumulates with walnut development. However, there is little literature about the lipid compositions and dynamic changes of WOBs during development. To address this gap in knowledge, lipidomics profile and metabolic modulation of WOBs during walnut (wen 185 cultivar) development (60, 74, 88, 102, 116, and 130 days after pollination, S1-S6) were analyzed using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). A total of 305 individual lipids in WOBs were mainly glycerolipids (79.34%), glycerophospholipids (12.13%), and fatty acyls (7.21%). Moreover, triacylglycerols, diacylglycerols, monoglycerides, free fatty acids, phosphatidylglycerols and phosphatidylcholines had high relative content. Notably, triacylglycerols were the most abundant lipids in WOBs at every stage and they were rich in unsaturated fatty acids, especially linoleic acid. With the walnut development, 209 lipids changed significantly between the S1 and S6 stages. The linoleic acid metabolism, glycerophospholipid metabolism and glycerolipid metabolism pathways were significantly enriched. Among the three metabolic pathways, linoleic acid metabolism had the greatest impact on WOBs formation and metabolism. Therefore, regulating linoleic acid metabolism would be one of the strategies to control the formation and metabolism of WOBs. Together, these findings contributed to further understanding of the potential mechanisms of lipid accumulation in WOBs. [Display omitted]