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The Transcription Factor at Regulates the Expression of Flavonoid Biosynthesis Genes in Transgenic Hop (Humulus lupulus L.)
A. Gatica-Arias, M. A. Farag, K.R. Hntzschel, J. Matouek, G. Weber

Metabolic engineering of the flavonoid biosynthesis pathway may be used for modifying nutritional and pharmaceutical properties of food crops as well as for producing ornamentals with novel color patterns. In plants, MYB transcription factors play a crucial role in regulating the biosynthesis of flavonoids. The AtMYB75/PAP1 is a member of the R2R3 MYB gene family and stimulates the expression of genes involved in the biosynthesis of flavonoids. Previously, AtMYB75/PAP1 from Arabidopsis thaliana L. was introduced into Humulus lupulus L. cv. Tettnanger plants by Agrobacterium-mediated genetic transformation. In this study, the copy number of AtMYB75/PAP1 was estimated in seven transgenic hop plants employing quantitative real-time PCR. Using this system it was demonstrated that each transgenic plant harbors only one copy of AtMYB75/PAP1. Moreover, the expression of genes CHS_H1, CHI, and F3'H in AtMYB75/PAP1 transgenic and wildtype hop plants was analyzed by reverse transcriptase quantitative real-time PCR. The expression of the structural genes CHS_H1, CHI, and F3'H was elevated in transgenic hop plants compared to the wildtype plants. Chemometric methods were successfully used to discriminate between wildtype and transgenic plants expressing the transcription factor AtMYB75/PAP1. These results revealed that the transcription factor AtMYB75/PAP1 activated the expression of these three genes essential for the biosynthesis of flavonoids in transgenic hop plants. Therefore, metabolic engineering using transcription factors, such as the MYB genes, may open the possibility for improving the content of pharmaceutically important secondary metabolites in hop.

Descriptors: hop, flavonoids, MYB transcription factor, quantitative real-time PCR, gene expression

BrewingScience - Monatsschrift fr Brauwissenschaft, 65 (July/August 2012), pp. 103-111