Down-regulation of β-carotene hydroxylase increases β-carotene and total carotenoids enhancing salt stress tolerance in transgenic cultured cells of sweetpotato

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Title
Down-regulation of β-carotene hydroxylase increases β-carotene and total carotenoids enhancing salt stress tolerance in transgenic cultured cells of sweetpotato
Author(s)
Sun Ha Kim; Young Ock Ahn; M J Ahn; Haeng Soon Lee; Sang Soo Kwak
Bibliographic Citation
Phytochemistry, vol. 74, no. 1, pp. 69-78
Publication Year
2012
Abstract
Sweetpotato (Ipomoea batatas Lam.) is an important industrial crop and source of food that contains useful components, including antioxidants such as carotenoids. β-Carotene hydroxylase (CHY-β) is a key regulatory enzyme in the beta-beta-branch of carotenoid biosynthesis and it catalyzes hydroxylation into both β-caroteneto β-cryptoxanthin and β-cryptoxanthin to zeaxanthin. To increase the β-carotene content of sweetpotato through the inhibition of further hydroxylation of β-carotene, the effects of silencing CHY-β in the carotenoid biosynthetic pathway were evaluated. A partial cDNA encoding CHY-β was cloned from the storage roots of orange-fleshed sweetpotato (cv. Shinhwangmi) to generate an RNA interference-IbCHY-β construct. This construct was introduced into cultured cells of white-fleshed sweetpotato (cv. Yulmi). Reverse transcription- polymerase chain reaction analysis confirmed the successful suppression of IbCHY-β gene expression in transgenic cultured cells. The expression level of phytoene synthase and lycopene β-cyclase increased, whereas the expression of other genes showed no detectable change. Down-regulation of IbCHY-β gene expression changed the composition and levels of carotenoids between non-transgenic (NT) and transgenic cells. In transgenic line #7, the total carotenoid content reached a maximum of 117 μg/g dry weight, of which β-carotenemeasured 34.43 μg/g dry weight. In addition, IbCHY-β-silenced calli showed elevated β-cryptoxanthin and zeaxanthin contents as well as high transcript level P450 gene. The 2,2-diphenyl-1- picrylhydrazyl radical scavenging activity (DPPH) in transgenic cells was more than twice that in NT cells. RNA-IbCHY-β calli increased abscisic acid (ABA) content, which was accompanied by enhanced tolerance to salt stress. In addition, the production of reactive oxygen species measured by 3,3′-diaminobenzidine (DAB) staining was significantly decreased in transgenic cultured cells under salt stress. Taken together, the present results indicate that down-regulation of IbCHY-β increased β-carotene contents and total carotenoids in transgenic plant cells and enhanced their antioxidant capacity.
Keyword
β-Caroteneβ-Carotene hydroxylaseCarotenoidMetabolic engineeringRNA interferenceSweetpotato
ISSN
0031-9422
Publisher
Elsevier
DOI
http://dx.doi.org/10.1016/j.phytochem.2011.11.003
Type
Article
Appears in Collections:
Division of Biomaterials Research > Plant Systems Engineering Research > 1. Journal Articles
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