Enhanced production of falcarinol-type polyacetylenes in hairy roots of cultivated carrot (Daucus carota subsp. sativus)

Polyacetylenes (PAs) are a large group of bioactive phytochemicals, which are primarily produced by higher plants of the families Apiaceae and Araliaceae. Especially aliphatic C17-polyacetylenes of the falcarinol-type such as falcarinol (FaOH) and falcarindiol (FaDOH) are known for their numerous positive effects on human health. In this study we investigate the potential of carrot hairy root cultures for production of PAs. Three individual plants of seven differently coloured carrot cultivars were used for the development of hairy root cultures by transformation of root discs with the wild-type Rhizobium rhizogenes strain 15834. A total of 51 individual hairy root (HR) lines were obtained and quantitatively analysed together with root, petiole and leaf tissue samples for FaOH and FaDOH. Among the five tissues sampled from the donor plants, root periderm samples generally exhibited the highest PA levels with FaDOH as prevailing PA and large differences between cultivars. In comparison to periderm tissue, FaOH levels were highly increased in HR lines of all cultivars. In contrast, FaDOH levels were not significantly altered. Considering the low to moderate PA concentration in root and leaf tissues of the orange cultivars there was an up to more than 10-fold increase of the FaOH concentration in HRs of these genotypes. Within this study a reproducible method for Rrhi-mediated transformation of carrot root discs was applied which provides an efficient tool to assess the function of candidate genes involved in the biosynthesis of key PAs in carrot but might be used in future also for the large-scale production of falcarinol-type PAs.