黏着箭菌JB19对菊苣幼苗铅镉抗性及黄酮生物合成的影响

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

摘要:

【目的】探讨耐重金属细菌对铅(lead, Pb)和镉(cadmium, Cd)胁迫下菊苣(Cichorium intybus L.)幼苗Pb、Cd抗性和黄酮生物合成的调控作用。【方法】在不同浓度Pb和Cd [(200+20) mg/kg、(400+40) mg/kg、(800+80) mg/kg]处理下，接种菌株JB19并测定菊苣幼苗生长指标、Pb和Cd含量、抗氧化酶活性、总黄酮含量和黄酮生物合成相关基因表达量。【结果】菌株JB19可显著提高不同浓度Pb和Cd处理下菊苣的生物量和叶绿素含量；减少氧化损伤，地上部和根部Pb、Cd含量均降低，其中在(Pb200+Cd20) mg/kg处理下H₂O₂和丙二醛(malondialdehyde, MDA)含量分别比对照降低了25.7%和26.1%，地上部Pb、Cd含量降低的幅度最大，分别降低了53.2%和54.1%；加强了菊苣幼苗的抗氧化酶防御系统，黄酮生物合成相关基因均显著上调，其中在(Pb400+Cd40) mg/kg处理下黄酮类化合物的含量增加了105.2%，查尔酮异构酶基因上调最显著，达458.9%。【结论】菌株JB19在减少植株体内重金属积累的同时，还可以通过增加植物生物量、抑制活性氧和膜脂过氧化水平、增强抗氧化酶活性和改变次级代谢产物黄酮类化合物的水平，提高菊苣幼苗的Pb、Cd抗性。

关键词:耐Pb和Cd细菌;Pb和Cd胁迫;菊苣;黄酮类化合物;基因表达

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.

Key words:Pb- and Cd-resistant bacteria;Pb and Cd stress;chicory;flavonoids;gene expression