%0 Journal Article
%T Silencing of beta-carotene hydroxylase increases total carotenoid and beta-carotene levels in potato tubers
%A Gianfranco Diretto
%A Ralf Welsch
%A Raffaela Tavazza
%A Fabienne Mourgues
%A Daniele Pizzichini
%A Peter Beyer
%A Giovanni Giuliano
%J BMC Plant Biology
%D 2007
%I BioMed Central
%R 10.1186/1471-2229-7-11
%X In this work, we silenced the non-heme beta-carotene hydroxylases CHY1 and CHY2 in the tuber. Real Time RT-PCR measurements confirmed the tuber-specific silencing of both genes . CHY silenced tubers showed more dramatic changes in carotenoid content than LCY-e silenced tubers, with beta-carotene increasing up to 38-fold and total carotenoids up to 4.5-fold. These changes were accompanied by a decrease in the immediate product of beta-carotene hydroxylation, zeaxanthin, but not of the downstream xanthophylls, viola- and neoxanthin. Changes in endogenous gene expression were extensive and partially overlapping with those of LCY-e silenced tubers: CrtISO, LCY-b and ZEP were induced in both cases, indicating that they may respond to the balance between individual carotenoid species.Together with epsilon-cyclization of lycopene, beta-carotene hydroxylation is another regulatory step in potato tuber carotenogenesis. The data are consistent with a prevalent role of CHY2, which is highly expressed in tubers, in the control of this step. Combination of different engineering strategies holds good promise for the manipulation of tuber carotenoid content.The biofortification of potato is a viable strategy for the eradication of a series of nutritional deficiencies, since this crop stands fourth, among staple foods, in yearly per capita consumption. Several efforts are under way for the metabolic engineering of potato carotenoid content [1-3]. In a companion paper, we reported the results of the tuber-specific silencing of the first dedicated step in lutein biosynthesis, LCY-e [3]. This resulted in increases of ¦Â-carotene (up to 14-fold) and of total carotenoids (up to 2.5-fold). No changes in carotenoid content, or in endogenous carotenoid gene expression, were observed in leaves, indicating that, in agreement with previous reports [1], gene silencing remains confined in tubers.Encouraged by this result, we decided to silence a second important regulatory step in carotenogenesi
%U http://www.biomedcentral.com/1471-2229/7/11