Enhancing the carotenoid content of Brassica napus seeds by downregulating lycopene epsilon cyclase.
The accumulation of carotenoids in higher plants is regulated by the environment, tissue type and developmental stage. In Brassica napus leaves, beta-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 beta rings such as beta-carotene, zeaxanthin and violaxanthin, while the other introduces both beta- and epsilon-rings in lycopene to form alpha-carotene and lutein. By reducing the expression of lycopene epsilon-cyclase (epsilon-CYC) using RNAi, we investigated altering carotenoid accumulation in seeds of B. napus. Transgenic seeds expressing this construct had increased levels of beta-carotene, zeaxanthin, violaxanthin and, unexpectedly, lutein. The higher total carotenoid content resulting from reduction of epsilon-CYC expression in seeds suggests that this gene is a rate-limiting step in the carotenoid biosynthesis pathway. epsilon-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.
Yu
Bianyun
B
Agriculture and Agri-Food Canada, Saskatoon Research Centre, 107 Science Place, Saskatoon, SK, Canada.
Lydiate
Derek J
DJ
Young
Lester W
LW
Schäfer
Ulrike A
UA
Hannoufa
Abdelali
A
D015139:Blotting, Southern; D029688:Brassica napus / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism*; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D015536:Down-Regulation; D005227:Fatty Acids / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D019753:Intramolecular Lyases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D014975:Lutein / Q000378:metabolism; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000378:metabolism*; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins; D019207:beta Carotene / Q000378:metabolism
D005227:Fatty Acids; D012333:RNA, Messenger; D018749:RNA, Plant; D034741:RNA, Small Interfering; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; D002338:Carotenoids; C005613:violaxanthin; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase; D014975:Lutein