Alterations in oleanolic acid and sterol content in marigold (Calendula officinalis) hairy root cultures in response to stimulation by selected phytohormones

Hairy root cultures are an efficient tool for the biotechnological production of plant metabolites and a convenient experimental model for analyzing the effect of various compounds on plant metabolism. In contrast to many other types of in vitro plant cultures, hairy roots do not require an external supply of phytohormones to the medium. Consequently, plant growth regulators such as auxins and cytokinins are rarely used as elicitors in hairy root in vitro cultures; however, they can strongly influence plant defense responses. The aim of this study was to investigate the influence of two auxins: natural indole-3-acetic acid (IAA) and synthetic 1-naphthaleneacetic acid (NAA), as well as two cytokinins: natural kinetin and synthetic 6-benzylaminopurine (BAP) at a concentration of 0.75 mg/L on the metabolism of sterols and triterpenoids in Calendula officinalis hairy roots. Auxins prevented the accumulation of triterpenoid saponins (oleanolic acid glycosides), while cytokinin BAP increased their accumulation by 17% and their release into the culture medium by a factor of 10. Other cytokinins and kinetins increased the sterol levels by 17%, the level of stigmasterol by 15%, and the level of isofucosterol by 7 times.