Downregulation of the lycopene epsilon-cyclase gene increases carotenoid synthesis via the β-branch-specific pathway and enhances salt-stress tolerance in sweetpotato transgenic calli

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Title
Downregulation of the lycopene epsilon-cyclase gene increases carotenoid synthesis via the β-branch-specific pathway and enhances salt-stress tolerance in sweetpotato transgenic calli
Author(s)
Sun Ha Kim; Yun Hee Kim; Y O Ahn; M J Ahn; Jae Cheol Jeong; Haeng Soon Lee; Sang Soo Kwak
Bibliographic Citation
Physiologia Plantarum, vol. 147, no. 4, pp. 432-442
Publication Year
2013
Abstract
Lycopene ε{lunate}-cyclase (LCY-ε{lunate}) is involved in the first step of the α-branch synthesis pathway of carotenoids from lycopene in plants. In this study, to enhance carotenoid synthesis via the β-branch-specific pathway [which yields β-carotene and abscisic acid (ABA)] in sweetpotato, the expression of IbLCY-ε{lunate} was downregulated by RNAi (RNA interference) technology. The RNAi-IbLCY-ε{lunate} vector was constructed using a partial cDNA of sweetpotato LCY-ε{lunate} isolated from the storage root and introduced into cultured sweetpotato cells by Agrobacterium-mediated transformation. Both semi-quantitative Reverse transcription polymerase chain reaction (RT-PCR) of carotenoid biosynthesis genes and high-performance liquid chromatography (HPLC) analysis of the metabolites in transgenic calli, in which the LCY-ε{lunate} gene was silenced, showed the activation of β-branch carotenoids and its related genes. In the transgenic calli, the β-carotene content was approximately 21-fold higher than in control calli, whereas the lutein content of the transgenic calli was reduced to levels undetectable by HPLC. Similarly, expression of the RNAi-IbLCY-ε{lunate} transgene resulted in a twofold increase in ABA content compared to control calli. The transgenic calli showed significant tolerance of 200 mM NaCl. Furthermore, both the β-branch carotenoids content and the expression levels of various branch-specific genes were higher under salt stress than in control calli. These results suggest that, in sweetpotato, downregulation of the ε{lunate}-cyclization of lycopene increases carotenoid synthesis via the β-branch-specific pathway and may positively regulate cellular defenses against salt-mediated oxidative stress.
ISSN
0031-9317
Publisher
Wiley
DOI
http://dx.doi.org/10.1111/j.1399-3054.2012.01688.x
Type
Article
Appears in Collections:
Jeonbuk Branch Institute > Biological Resource Center > 1. Journal Articles
Division of Research on National Challenges > Plant Systems Engineering Research > 1. Journal Articles
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