The road of lipid migration in flaxseed (Linum usitatissimum L.) during germination

Abstract

Lipids are essential sources of carbon and energy during flaxseed germination; however, the dynamic changes in key lipid metabolites, pathways, and their locations remain unclear. This study revealed that oil bodies migrated from well-distributed locations to the cell wall between 0–2 d, with cell contours gradually blurring during 2–3 d, initiating the germination process. Subsequently, the order of oil body migration was leaf > stem > root during 4–7 d. This study established lipid metabolite pathway networks to elucidate the underlying mechanisms of the interconversion of active lipid metabolites. Phosphatidyl methyl ethanolamines (PMEs) (18:2/23:0), (24:0/18:2), and (24:0/18:3) were utilized as energy substrates through α-linolenic acid metabolism, autophagy, and glycosylphosphatidylinositol (GPI)-anchor biosynthesis pathways during 2–3 d. The production of phosphatidic acid (PA) (18:1/18:1) exceeded its consumption in glycerolipid metabolism, glycerophospholipid metabolism, and the phosphatidylinositol signaling system, resulting in the consumption of phosphatidylethanolamine (PE) ((16:0/16:0), (24:0/24:0)) during 3–4 d. The active metabolite phosphatidylcholine (PC) (18:1/18:1) converted to PA and PE in leaves, stems, and roots and to triacylglycerol (TG) in stems and roots during 4–6 d. Oil bodies existed in leaves (ceramide (Cer), TG) and roots (TG) during 6–7 d. These findings elucidate the metabolic processes underlying seedling development, paving the way for crop improvement.