Endophytic Pseudomonas fluorescens induced sesquiterpenoid accumulation mediated by gibberellic acid and jasmonic acid in Atractylodes macrocephala Koidz plantlets

Abstract

Atractylodes macrocephala is a traditional Chinese medicinal plant, its main bioactive components were sesquiterpenoids. An endophytic bacterium Pseudomonas fluorescens ALEB7B isolated from the stem of Atractylodes lancea was found to enhance sesquiterpenoid content by 20–74% in the root of A. macrocephala. However, the mechanism of endophytes inducing secondary metabolites biosynthesis in A. macrocephala is unknown. To elucidate the signaling mechanism and molecular basis of ALEB7B induced-sesquiterpenoid accumulation in A. macrocephala, the signaling involved in this process and the activity of key enzymes 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) were detected. The results showed that gibberellic acid (GA) and jasmonic acid (JA) signals cooperatively contributed to the bacterium inducing sesquiterpenoid accumulation. The bacterium, JA and GA signals can increase the activities of both HMGR and DXR. By comparing the results of endophytic bacterium interactions with A. lancea, we found that ALEB7B can enhance the sesquiterpenoids content in A. macrocephala and A. lancea; however, the responsive signaling pathways induced by ALEB7B in A. macrocephala and A. lancea were different. In conclusion, endophytes may enhance sesquiterpenoid production in A. macrocephala plants by modulating the GA and JA signaling pathways. This study found that Pseudomonas fluorescens ALEB7B can efficiently promote sesquiterpenoid accumulation in Atractylodes macrocephala root by inducing GA and JA bursting and increasing activities of HMGR and DXR.