Effect of jasmonic acid and chitosan on triterpenoid production in Calendula officinalis hairy root cultures

Two lines of Calendula officinalis in vitro hairy root culture, obtained as a result of transformation with the wild type Agrobacterium rhizogenes strain ATCC 15834, were subjected to elicitation by jasmonic acid and chitosan in the context of possible stimulation of biosynthesis, accumulation and secretion of triterpenoids. Jasmonic acid was found to be a very effective elicitor, increasing both the accumulation of oleanolic acid saponins in the hairy root tissue (up to 20-fold) and, in particular, the secretion of these compounds to the medium (up to 113-fold). However, it also promoted inhibition in biosynthesis and accumulation of sterols (approximately by 60%) with some alterations of their profile. Chitosan slightly enlarged the accumulation and secretion of oleanolic acid saponins (up to 3-fold) and simultaneously, increased the sterols total content of (by 5-18%), with some changes of the ratio among individual compounds being observed. The obtained results revealed that the mechanism of action and impact on plant metabolism of the two applied biotic elicitors is different, which have consequences in their efficiency to stimulate triterpenoid production. The trials of stimulation of triterpenoid biosynthesis in plants and plant in vitro cultures often concern the possible competition of pathways leading to sterols and triterpenoids. Some symptoms of the switch at a branch point between primary and secondary triterpenoid metabolism are clearly visible in the response of C. officinalis hairy roots stimulation with jasmonic acid and chitosan.