Differentiation in Post-harvest Lipid Metabolism of Oil Palm Fruits

Objective  Mechanism and accumulation of lipid synthesis in thin-shelled oil palm fruits was investigated for breeding of variety resistant to fat rancidity.

Method  Fruits of thin-shelled oil palm freshly harvested 185d after pollination (T1), 24h post-harvest (T2), and 36h post-harvest (T3) were collected for LC-MS/MS and RNA-seq determination and analysis on lipid metabolites and differentially expressed genes in mesocarp of oil palm fruits as the lipid oxidation taking place.

Result  In the fruit development, 5 lipid classes, 23 lipid subclasses, and 520 monomer molecules in mesocarp of the oil palm fruits were identified. It is well known that the hydrolysis of phosphatidylcholine (PC) is a lipid oxidation and the hydrolyzed glycerophosphate choline (GPC) affects PC, lipophosphatase (LPP) promotes synthesis of phosphates and glycerophospholipids, and the expression of chlorophyll relates to chlorophyll content. This study found that the aldehyde dehydrogenase (ALDH7A1 and ALDH2), monoacylglycerol lipase (MGL), phospholipase A1 (PLA1), and glycerophosphodiester phosphodiesterase (GDPD1) significantly negatively correlated with glycerophospholipids, such as diacylglycerol trimethyl homoserine (DGTS), phosphatidic acid (PA), phosphatidylinositol (PI), phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), but significantly positively correlated with palmitic acid, while GDPD1, LPP, and digalactosylglycerol synthase (DGD1) significantly positively correlated with the glycerophospholipids, such as DGTS, PA, PI, PC, PG, PE, but negatively correlated with palmitic acid, whereas MGL monoglyceride (MG) extremely significantly positively correlated with linoleic acid (LA) but significantly negatively correlated with ceramide (Cer), and DGD1 and LPP significantly negatively correlated with MG and LA, but significantly positively correlated with Cer.

Conclusion  It appeared that ALDH7A1, ALDH2, PLA1, and MGL inhibited the glycerophospholipids synthesis but promoted the synthesis of fatty acids such as palmitic acid, while DGD1, LPP, and GDP1 enhanced the synthesis of glycerophospholipids but retarded that of palmitic and other fatty acids.