title: Down-regulation of sweetpotato lycopene β-cyclase gene enhances tolerance to abiotic stress in transgenic calli.
abstract: Lycopene β-cyclase (LCY-β) is a key enzyme involved in the synthesis of α- and β-branch carotenoids such as α-carotene and β-carotene through the cyclization of lycopene. IbLCY-β had a length of 1,506 bp and approximately 80 % nucleotide sequence identity with that of tomato LCY-β. IbLCY-β was strongly expressed in leaves, and expression was enhanced by salt-stress and osmotic-stress conditions. To characterize the LCY-β gene (IbLCY-β) of sweetpotato (Ipomoea batatas), it was isolated and transformed into calli of white-fleshed sweetpotato using an IbLCY-β-RNAi vector. Transgenic IbLCY-β-RNAi calli had yellow to orange color and higher antioxidant activity compared to that of white, nontransgenic (NT) calli. Transgenic cells had significantly higher contents of total carotenoids, although lycopene was not detected in transgenic or NT cells. All transgenic calli had strongly activated expression of carotenoid biosynthetic genes such as β-carotene hydroxylases (CHY-β), cytochrome P450 monooxygenases (P450), and carotenoid cleavage dioxigenase 1 (CCD1). Transgenic cells exhibited less salt-induced oxidative-stress damage compared to that of NT cells, and also had greater tolerance for polyethylene glycol (PEG)-mediated drought compared to that of NT cells, due to the higher water content and reduced malondialdehyde (MDA) content. The abscisic acid content was also higher in transgenic cells. These results show that a study of IbLCY-β can facilitate understanding of the carotenoid biosynthetic pathway in sweetpotato. IbLCY-β could be useful for developing transgenic sweetpotato enriched with nutritional carotenoids and with greater tolerance to abiotic stresses.
authors.affiliation: Plant Systems Engineering Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Gwahak-ro 125, Daejeon, 305-806, Korea.
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Kim
authors.forename: Jae Cheol
authors.initials: JC
authors.lastname: Jeong
authors.forename: Seyeon
authors.initials: S
authors.lastname: Park
authors.forename: Ji-Yeong
authors.initials: JY
authors.lastname: Bae
authors.forename: Mi-Jeong
authors.initials: MJ
authors.lastname: Ahn
authors.forename: Haeng-Soon
authors.initials: HS
authors.lastname: Lee
authors.forename: Sang-Soo
authors.initials: SS
authors.lastname: Kwak
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D002338:Carotenoids / Q000096:biosynthesis*; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D019753:Intramolecular Lyases / Q000235:genetics* / Q000378:metabolism*; D027723:Ipomoea batatas / Q000201:enzymology / Q000235:genetics*; D000077276:Lycopene; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D011092:Polyethylene Glycols / Q000494:pharmacology; D055049:Salt Tolerance; D013312:Stress, Physiological
chemical_list: D010940:Plant Proteins; D002338:Carotenoids; D011092:Polyethylene Glycols; D000040:Abscisic Acid; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase; D000077276:Lycopene