Elicitation of Flavonoids in Kalanchoe pinnata by Agrobacterium rhizogenes-Mediated Transformation and UV-B Radiation

Kalanchoe pinnata from the stonecrop family (Crassulaceae) is a medicinal plant with high content of bioactive compounds. The plant is known for its anti-allergic, antioxidant, anti-inflammatory, antimicrobial and antibacterial activities, which are mainly attributed to flavonoids. Low yields of bioactive compounds in medicinal plants have led to new strategies for enhancing their biosynthetic capacity in order to increase the content of specialized metabolites. Herein, the accumulation of specialized metabolites in plants can be triggered by elicitation methods. In the current study, different elicitation strategies were conducted towards the enhancement of bioactive compounds in K. pinnata leaves. We investigated the effect of natural transformation with the Agrobacterium rhizogenes strain A4 as means of biological elicitation on the total content of flavonoids in the leaves of K. pinnata. Furthermore, the effect of supplemental UV-B radiation, as physical elicitor, was assessed on the total flavonoid content of both wild-type (WT) and rol-transformed plants. The combined effect of the two mentioned elicitation methods was also examined. The data showed that presence of rol genes resulted in an increase of 24% in the total flavonoid content compared to WT plants. The supplemental UV-B radiation increased the total content of flavonoids with 95% and 89% in the WT and the rol+ plants, respectively. Collectively, a synergistic effect was shown as the combination of the two factors dramatically increased (133%) the total flavonoid content in K. pinnata leaves.