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Agrobacterium Rhizogenes-Mediated Transformation of Hop (Humulus lupulus L. cv. Tettnanger): Establishment of a System for Functional Evaluation of Genes
A. Gatica-Arias, N. Amma, M. Stanke, G. Weber

Secondary metabolites produced in the lupulin glands (glandular trichomes) of hop cones are important for beer production, and for the pharmaceutical and medicinal industry. However, in wildtype plants the concentration of these compounds is rather low. To enhance their production, it would be interesting to modify by genetic transformation the regulation of genes involved in the biosynthesis of flavonoids and phloroglucinols. Although genetic transformation of hop has been used successfully for some time, it is a laborious and time consuming process. Therefore, the development of a simple and fast assay for functional validation of candidate genes is very desirable. As an alternative A. rhizogenes-mediated transformation could be employed for stably expressing genes in hairy roots. The latter being morphologically related to trichomes. A. rhizogenes K599 and 15834 were tested for their ability to induce the formation of hairy roots on hop explants. Only A. rhizogenes 15834 was able to induce hairy roots after 12-27 days of culture. The highest percentage of explants with roots as well as the total number of roots were obtained when infected leaf segments were cultivated with the adaxial surface in contact with the culture medium. Transgenic hairy roots were verified by GUS staining. The integration of rolC and mgfp5 genes in transgenic hairy roots was confirmed by PCR. We developed a system to investigate the role of genes and transcription factors involved in the biosynthesis of flavonoids and phloroglucinols.

Descriptors: hop, Humulus lupulus, Agrobacterium rhizogenes, genetic transformation

BrewingScience - Monatsschrift für Brauwissenschaft, 65 (July/August 2012), pp. 91-95