Bioactive metabolites in Codonopsis pilosula are of particular interest as an immunostimulant. Methyl jasmonate (MeJA) plays an important role in the elicitation of metabolite biosynthesis. Here, we explored the response of metabolites to MeJA elicitation in C. pilosula adventitious roots and multiple shoots. The results showed that the biomass, polysaccharide, and lobetyolin content of adventitious roots exhibited the highest increases with 100 µmol·L⁻¹ MeJA at the 16th day of subculture, whereas the atractylenolide III (a terpenoid) content increased extremely with 50 µmol·L⁻¹ MeJA treatment at the 7th day of subculture. In addition, the biomass and lobetyolin content significantly increased at the 4th day after treatment. Similarly, the polysaccharide and lobetyolin content increased in multiple shoots. Further identification of different metabolites responding to MeJA by ¹H-NMR showed an extremely significant increase of the lobetyolinin level, which coincided with lobetyolin. Accordingly, the precursor, fatty acids, showed a highly significant decrease in their levels. Furthermore, a significant increase in β-d-fructose-butanol glycoside was detected, which was accompanied by a decrease in the sucrose level. Accordingly, the enzyme genes responsible for terpenoid and carbohydrate biosynthesis, CpUGPase, and CpPMK, were up regulated. In conclusion, MeJA promoted culture growth and accelerated bioactive metabolite accumulation by regulating the expression of the metabolite biosynthesis related genes, CpUGPase and CpPMK in C. pilosula.

The aim of this study was to explore the beneficial effects of endophytic Pseudomonas poae strain S61 on medicinal plant Astragalus mongholicus. Growth and production of indoleacetic acid (IAA) of the strain was firstly characterized under stress conditions, demonstrating that the strain performance was more robust in the medium containing 20% PEG6000. Beneficial effects of the strain on host seedlings were then investigated by pouring 20% PEG6000 for 3 weeks to mimic drought stress. Among growth parameters, root biomass and root-shoot ratio were significantly enhanced by the combination of 20% PEG6000 with the strain inoculation while the individual trial had no effect. The combination trial also increased calycosin-7-O-glucoside and ononin accumulations in the roots, suggesting that the strain executed beneficial effects on A. mongholicus only when it grew under drought stress. Using MDA as lipid peroxidation parameter, our result indicated that leaf lipid peroxidation should be involved in the process.