Carotenoid composition and sequestration in cassava (Manihot esculentum Crantz) roots

Cassava ( Manihot esculentum Crantz ) is a staple food source for many developing countries. Its edible roots are high in starch but lack micronutrients such as β-carotene. In the present study, analysis of pedigree breeding populations has led to the identification of cassava accessions with enhanced β-carotene contents up to 40 μg/g DW. This represents 0.2% of the Recommended Daily Allowance (RDA) for vitamin A. The β-branch of the carotenoid pathway predominates in cassava roots, with dominant levels of β-carotene followed by other minor epoxides of β-ring derived carotenoids. Metabolomic analysis revealed that steady state levels of intermediary metabolism were not altered by the formation of carotenoids, similar to starch and carbohydrate levels. Apocarotenoids appeared to be independent of their carotenoid precursors. Lipidomic analysis provided evidence of a significant positive correlation between carotenoid and lipid content, in particular plastid specific galactolipids. Proteomic analysis of isolated amyloplasts revealed an abundance of carbohydrate/starch biosynthetic associated proteins (e.g. glucose-1-phosphate adenylyltransferase). No carotenoid related proteins were detected even in the highest carotenoid containing lines. Carotenoids were associated with fractions typically annotated as plastoglobuli and plastid membranes (particularly the envelope). Proteomic analysis confirmed these structures apart from plastoglobuli, thus potentially amyloplast structures may not contain classical plastoglobuli structures. Highlight Cassava genotypes with enhanced provitamin A content (β-carotene) reveals interconnectivity between the carotenoid pathway, starch and lipid biosynthesis. ### Competing Interest Statement The authors have declared no competing interest. * CIAT : International Center for Tropical Agriculture DAG : diacylglycerides DGDG : digalactosyldiacylglycerol DW : dry weight GC-MS : gas chromatography mass spectrometry HexCer : hexoside ceramide LC-MS : liquid chromatography mass spectrometry MAG : monoacylglycerides MGDG : Monogalactosyldiacylglycerol MPS : multipurpose sampler NIRS : near infra-red spectroscopy OR : orange PA : phosphatidic acid PC : phosphatidyl choline PCA : principal component analysis PCs : principal components PE : phosphatidyl ethanolamine PG : phosphatidyl glycerol PI : phosphatidyl inositol PSY : phytoene synthase pVA : precursor for Vitamin A RDA : Recommended Daily Allowance SDS-PAGE : Sodium dodecyl-sulphate polyacrylamide gel electrophoresis SPME : solid phase microextraction SQDG : sulfoquinovosyldiacylglycerol Susy : sucrose synthase TAG : triacyl glycerol TCA : tricarboxylic acid UPLC-DAD : ultra-pressure liquid chromatography – diode array detector VAD : Vitamin A deficiency