Enhancing the carotenoid content of Brassica napus seeds by downregulating lycopene epsilon cyclase

• Published in: Transgenic research 2008-08, Vol.17 (4), p.573-585
• Main Authors: Yu, Bianyun, Lydiate, Derek J, Young, Lester W, Schäfer, Ulrike A, Hannoufa, Abdelali
• Format: Article
• Language: English
• Subjects: Animal Genetics and Genomics; beta Carotene - metabolism; Biological and medical sciences; Biomedical and Life Sciences; Biomedical Engineering/Biotechnology; Biotechnology; Blotting, Southern; Brassica napus; Brassica napus - genetics; Brassica napus - metabolism; carotenoids; Carotenoids - metabolism; Chromatography, Gas; Chromatography, High Pressure Liquid; Down-Regulation; Fatty Acids - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Genetic Engineering; Genetic technics; Intramolecular Lyases - antagonists & inhibitors; Intramolecular Lyases - genetics; Intramolecular Lyases - metabolism; Life Sciences; Lutein - metabolism; Lycopene ε-cyclase; Methods. Procedures. Technologies; Molecular Medicine; Original Paper; Plant Genetics and Genomics; Plants, Genetically Modified; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Plant - genetics; RNA, Plant - metabolism; RNA, Small Interfering - pharmacology; RNAi silencing; seeds; Seeds - genetics; Seeds - metabolism; Transgenic animals and transgenic plants; Transgenics; Xanthophylls - metabolism; Zeaxanthins
• ISSN: 0962-8819; 1573-9368
• DOI: 10.1007/s11248-007-9131-x

The accumulation of carotenoids in higher plants is regulated by the environment, tissue type and developmental stage. In Brassica napus leaves, β-carotene and lutein were the main carotenoids present while petals primarily accumulated lutein and violaxanthin. Carotenoid accumulation in seeds was developmentally regulated with the highest levels detected at 35-40 days post anthesis. The carotenoid biosynthesis pathway branches after the formation of lycopene. One branch forms carotenoids with two β rings such as β-carotene, zeaxanthin and violaxanthin, while the other introduces both β- and ε-rings in lycopene to form α-carotene and lutein. By reducing the expression of lycopene ε-cyclase (ε-CYC) using RNAi, we investigated altering carotenoid accumulation in seeds of B. napus. Transgenic seeds expressing this construct had increased levels of β-carotene, zeaxanthin, violaxanthin and, unexpectedly, lutein. The higher total carotenoid content resulting from reduction of ε-CYC expression in seeds suggests that this gene is a rate-limiting step in the carotenoid biosynthesis pathway. ε-CYC activity and carotenoid production may also be related to fatty acid biosynthesis in seeds as transgenic seeds showed an overall decrease in total fatty acid content and minor changes in the proportions of various fatty acids.