Effects of PAL and ICS on the production of total flavonoids, daidzein and puerarin in Pueraria thomsonii Benth. suspension cultures under low light stress

Under stress, some secondary metabolites are synthesized and accumulated in plants. Salicylic acid, which is synthesized through phenylalanine ammonia-lyase and isochorismate synthase, is involved in this response to stress. However, the effects of phenylalanine ammonia-lyase and isochorismate synthase on the total flavonoids and desirable isoflavonoids in plants under stress remain unknown. In this study, the effects of phenylalanine ammonia-lyase and isochorismate synthase on total flavonoids, daidzein and puerarin in Pueraria thomsonii Benth. under low light stress were investigated. When the phenylalanine ammonia-lyase activity was inhibited by l-AOPP, the salicylic acid content was not reduced, but gradually increased along with an increase of isochorismate synthase activity. The trends of salicylic acid and total flavonoid content were similarly consistent, but there was no significant positive correlation between phenylalanine ammonia-lyase suppression and total flavonoid production in P. thomsonii under low light stress. However, daidzein synthesis was correlated with the isochorismate synthase pathway, and puerarin with the phenylalanine ammonia-lyase pathway.