Fatty acid isoprenoid alcohol ester synthesis in fruits of the African Oil Palm (Elaeis guineensis). (May 2021) - Gutbrod, Philipp
Abstract: The African Oil Palm ( Elaeis guineensis ; family Arecaceae) represents the most important oil crop for food and feed production and for biotechnological applications. Two types of oil can be extracted from palm fruits, the mesocarp oil which is rich in palmitic acid and in carotenoids (provitamin A) and tocochromanols (vitamin E), and the kernel oil with high amounts of lauric and myristic acid. We identified fatty acid phytyl esters (FAPEs) in the mesocarp and kernel tissues of mature fruits, mostly esterified with oleic acid and very long chain fatty acids. In addition, fatty acid geranylgeranyl esters (FAGGEs) accumulated in mesocarp and kernels to even larger amounts. In contrast, FAPEs and FAGGEs amounts and fatty acid composition in leaves were very similar. Analysis of wild accessions of African Oil Palm from Cameroon revealed a considerable variation in the amounts and composition of FAPEs and FAGGEs in mesocarp and kernel tissues. Exogenous supplementation of phytol or geranylgeraniol to mesocarp slices resulted in the incorporation of these alcohols into FAPEs and FAGGEs, respectively, indicating that they are synthesized via enzymatic reactions. Three candidate genes of the esterase/lipase/thioesterase (ELT) family were identified in the Oil Palm genome. The genes are differentially expressed in mesocarp tissue with EgELT1 showing the highest expression. Geranylgeraniol from FAGGE might be recycled and used as a substrate for the synthesis of carotenoids and tocotrienols during fruit development. Thus, FAPEs and FAGGEs in the mesocarp and kernel of Oil Palm provide an additional metabolic source for fatty acids and phytol or geranylgeraniol, respectively. Graphical abstract: The oil from mesocarp of African Oil Palm contains different fatty acid esters of geranylgeraniol or phytol. Image 1 Highlights: The African Oil Palm ( Elaeis guineensis ) contains esters of fatty acids with the isoprenoids phytol or geranylgeraniol. The composition of isoprenoid esters differs in the mesocarp and kernel tissues of the fruits. Different oil palm accessions show a distinct composition of phytyl and geranylgeranyl esters. Three candidate genes of the ELT family were identified potentially involved in isoprenoid ester synthesis.