Effect of Ensifer adhaerens JB19 on lead and cadmium resistance and flavonoid synthesis in chicory (Cichorium intybus) seedlings

Abstract:

[Objective] To investigate the regulatory effect of the heavy metal-resistant bacteria on lead (Pb) and cadmium (Cd) resistance and flavonoid biosynthesis in chicory (Cichorium intybus L.) seedlings under Pb and Cd stress. [Methods] After inoculation of Ensifer adhaerens JB19, the growth indicators, the content of Pb and Cd, the activities of antioxidant enzymes, the content of total flavonoids, and the expression of genes related to flavonoid biosynthesis in the chicory seedlings exposed to different concentrations of Pb and Cd ((200+20) mg/kg, (400+40) mg/kg, (800+80) mg/kg) were determined. [Results] Strain JB19 significantly increased the biomass and chlorophyll content of chicory seedlings exposed to different concentrations of Pb and Cd. Under the Pb+Cd treatment of (200+20) mg/kg, the inoculation of strain JB19 decreased the content of H₂O₂, MDA, and Pb and Cd in the shoot by 25.7%, 26.1%, 53.2%, and 54.1%, respectively, compared with the control. Moreover, the strain strengthened the antioxidant enzyme system and up-regulated expression of the genes involved in flavonoid biosynthesis of chicory seedlings. Under the Pb+Cd treatment of (400+40) mg/kg, the strain increased the flavonoid content by 105.2% and up-regulated the expression of chalcone isomerase gene to reach 458.9%. [Conclusion] E. adhaerens JB19 can reduce the accumulation of heavy metals and improve the Pb and Cd resistance of chicory seedlings by increasing plant biomass, reducing active oxygen, inhibiting membrane lipid peroxidation, enhancing the activities of antioxidant enzymes, and regulating the levels of flavonoids.