Effect of Elicitors on Phenylpropanoid Biosynthesis in Hairy Roots of Prunella Vulgaris

Phenylpropanoids are economically important secondary metabolites with strong pharmacological activity substantively, and their pathways often can be adjusted by abiotic elicitors in plant tissue cultures. Silver nitrate, copper chloride, salicylic acid, and hydrogen peroxide affect the phenylpropanoid such as rosmarinic acid (RA) in hairy root (HR) cultures of Prunella vulgaris. Hairy roots (HRs) were developed via Agrobacterium rhizogenes mediated transformation and cultured under dark and agitated conditions. After treatment for 3 days, we used HPLC to quantify four phenylpropanoids, caffeic acid, benzoic acid, rutin, and quercetin from the treatments with different concentrations of elicitors. The most potent elicitor was salicylic acid which increased total phenols by 46.7±1.38 μg/g in control to 95.46±12.63 μg/g at 0.5 mM, largely on account of a nearly threefold increase in caffeic acid (32.15±5.67 μg/g) and a doubled rutin (59.64±6.71 μg/g) level. At 0.5 mM CuCl2, the accumulation of phenols was increased (64.83±2.62 μg/g), due mainly to an increase in rutin levels (45.46±2.11 μg/g) and caffeic acid (13.18±0.04 μg/g). At a concentration of 1mg/L AgNO3, the production of caffeic acid and quercetin was moderately induced (47.01±1.87 μg/g) but suppressed at higher concentrations. The H2O2 treatments demonstrated a low-level elicitation effect with total phenolics maximum of 48.93±1.21 μg/g (100 mM), and a more gradual induction of benzoic acid (1.6±0.16 μg/g) and rutin (32.27±0.16 μg/g). Overall quercetin content decreased in nearly all the treatments and was especially evident at high concentrations of SA and AgNO3, supporting the notion that a metabolic reprogramming with subsequent precursor diversion is occurring. These findings demonstrate that different abiotic elicitors differentially regulate the phenylpropanoid biosynthesis of P. vulgaris HRs, and that SA and CuCl2 were very strong inducers, providing probable strategies to improve the production of medicinally important phenolic compounds.