Production of guaianolides in Agrobacterium rhizogenes - transformed chicory regenerants flowering in vitro

•Chicory transformation with A. rhizogenes is easy and efficient.•More guaianolides are produced in fast growing hairy root cultures.•Whole plant regeneration from hairy roots and flowering in vitro are spontaneous.•Floral transition stimulates guaianolides accumulation only in transformed plants.•The expression of RolC correlates with the production of guaianolides. Chicory (Cichorium intybus L.) is rich in bitter sesquiterpene lactones, mainly guaianolides: lactucin, 8-deoxylactucin, lactupicrin and their 11(S),13-dihydroderivatives—compounds recognized for their antimicrobial and anti-cancer effects. In vitro plant tissue culture, and particularly Agrobacterium rhizogenes—generated hairy root (HR) cultures, have many advantages as systems for production of valuable secondary metabolites. Although chicory HRs grow better than control culture, having nearly 60 times greater fresh weight gain, they do not contain a higher content of guaianolides than wild type (wt) roots. Thus we have established in vitro system comprised of wt root and HR cultures, and wt and transformed regenerated plants of the same age, in rosette and flowering stage, in order to study the effects of transformation, organogenesis and flowering on guaianolides production. Both regeneration and flowering in vitro were spontaneous, so the results were not influenced by exogenous growth regulators. Some of the transformed clones grew better, but all flowered earlier in comparison to wt plants. Floral transition increased guaianolides content in both roots and leaves of transformed, but not of wt plants. Expression of RolC oncogene correlated with floral transition and with guaianolides accumulation. We propose A. rhizogenes—transformed plants at the flowering stage as an alternative source of free guaianolides, where, in contrast to HRs, entire plants can be used for the extraction.