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Open Access Highly Accessed Research article

Metabolic engineering of potato tuber carotenoids through tuber-specific silencing of lycopene epsilon cyclase

Gianfranco Diretto1, Raffaela Tavazza1, Ralf Welsch2, Daniele Pizzichini1, Fabienne Mourgues1, Velia Papacchioli1, Peter Beyer2 and Giovanni Giuliano1*

Author Affiliations

1 ENEA, Casaccia Research Center, PO Box 2400, Roma 00100AD, Italy

2 Center for Applied Biosciences, Universität Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany

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BMC Plant Biology 2006, 6:13  doi:10.1186/1471-2229-6-13

Published: 26 June 2006

Abstract

Background

Potato is a major staple food, and modification of its provitamin content is a possible means for alleviating nutritional deficiencies. beta-carotene is the main dietary precursor of vitamin A. Potato tubers contain low levels of carotenoids, composed mainly of the xanthophylls lutein, antheraxanthin, violaxanthin, and of xanthophyll esters. None of these carotenoids have provitamin A activity.

Results

We silenced the first dedicated step in the beta-epsilon- branch of carotenoid biosynthesis, lycopene epsilon cyclase (LCY-e), by introducing, via Agrobacterium-mediated transformation, an antisense fragment of this gene under the control of the patatin promoter. Real Time measurements confirmed the tuber-specific silencing of Lcy-e. Antisense tubers showed significant increases in beta-beta-carotenoid levels, with beta-carotene showing the maximum increase (up to 14-fold). Total carotenoids increased up to 2.5-fold. These changes were not accompanied by a decrease in lutein, suggesting that LCY-e is not rate-limiting for lutein accumulation. Tuber-specific changes in expression of several genes in the pathway were observed.

Conclusion

The data suggest that epsilon-cyclization of lycopene is a key regulatory step in potato tuber carotenogenesis. Upon tuber-specific silencing of the corresponding gene, beta-beta-carotenoid and total carotenoid levels are increased, and expression of several other genes in the pathway is modified.