| Atractylodes macrocephala Koid and Atractylodes lancea(Thunb.DC),both are belong to Atractylodes genuine of the Composite family,their dried rhizome are usually treated as the traditional chinese medicine.They are medicinal plants with similar origin.A.macrocephala was mainly produced in Zhejiang province,and A.lancea was mainly produced in Jiangsu province.What’s more,their medicinal active components are similar in composition and structure,and the main medicinal components include volatile oil substances(such as zingiberene,β-sesquiphellandren,and atractylone)and lactone(like atractylenolide).There are abundant endophytes resources in medicinal plants,and some of them have important effects on the accumulation of plant secondary metabolites.As for the interaction between endophytes and the host,the current research mostly focuses on the influence of endophytes on the host,including single strain inoculation or compound colony inoculation.However,there are little reports on the interaction between plant endophytes and cross-species plants.It is easy to ignore the synergistic effect of endophytes and cross-species host mutualism,as well as the complexity and diversity of their interaction relationship.Previously,our team has explored the endophytic bacterial resources of A.lancea and revealed the signal molecules involved in the process of the endophytic bacteria inducing the volatile oil accumulation in A.lancea.Therefore,in this study,we took A.macrocephala and A.lancea as the model plants,the same genus plantlets,and the dominant endophytic bacteria isolated from A.macrocephala and A.lancea as the model strains,to explore the influence of endophytic bacteria on secondary metabolites accumulation of species from the same genus and the difference of resopnsing signal molecules in two species.Firstly,we isolated endophytic bacteria from A.macrocephala by pure culture method,identified by 16 S r DNA sequencing,and screened out strains with the function of promoting the active ingredients accumulation in medicinal plants by detecting their plant viability.A total of 49 endphytic bacteria were isolated from A.macrocephala,including Bacillus sp.,Pseudomonas sp.,Lysinibacillus sp.,Aneurinibacillus sp.,Briefbacillus sp.,Microbacterium sp.,Enterobacter sp.,Oerskscribe sp.,Xanthomonas sp.,Olivibacter sp.and Paenarthrobacter sp.Among them,Bacillus sp.and Pseudomonas sp.are the dominant bacteria in A.macrocephala.Among the isolates,the strain’s number being capable of fixing nitrogen,dissolving phosphorus and potassium were 10,25 and 19 respectively,and35 strains were capable of synthesizing indoleacetic acid.By analysing,we obtained several strains of endophytic bacteria isolated from A.macrocephala with strong ability to fix nitrogen,dissolve phosphorus,dissolve potassium and synthesize indoleacetic acid,which may have the potential to promote plant growth and volatile oil accumulation.This study provides the basis for revealing the mechanism of endophytic bacteria and host interaction in A.macrocephala.Secondly,we screened out an endophytic bacteria isolated from A.macrocephala with good ability of plant-growth-promoting to establish patterns of “Bacteria from A.macrocephala – A.macrocephala” and “Bacteria from A.macrocephala – A.lancea”.The effects of volatile oil accumulation and the similarities and differences of signal molecules induced by bacteria in trans-species plants were analyzed.By innoculation,B.endophyticus AMR83 was selected as the most effective bacterium inducing volatile oil accumulation in Atractylodes plants in a certain time,which incresead volatile oil content of A.macrocephala and A.lancea by 100.5% and 50.4%respectively.Indoleacetic acid and salicylic acid signaling molecules resonsed to AMR3 both in A.macrocephala and A.lancea,but there was time difference in the response process.In addition,the AMR83 also increased the gibberellic acid content in the shoot of A.lancea,while no significant effect on GA level of A.macrocephala.This indicates that there are differences in the signaling molecules induced by endophytic bacteria in A.macrocephala and A.lancea.Finally,we selected a strain named P.fluorescens ALEB7 B,which has been reported can significantly increase host volatile oil accumulation and its signaling mechanism has been revealed.We established an "endophytic bacteria from A.lancea-A.macrocephala" system and analyzed the physiological mechanism of ALEB7 B on the volatile oil accumulation in A.macrocephala,and finally we compared the differences of signal molecular induced by ALEB7 B in two Atractylodes plants.The study found that the endophytic bacterium P.fluorescens ALEB7 B isolated from the stem of A.lancea increased the volatile oil content in root of A.macrocephala by 74%.To elucidate its induction mechanism,we analyzed the signaling pathways involved in this process and the activities of the terpenoids key synthase HMGR and DXR.The results showed that ALEB7 B induced gibberellic acid(GA)and jasmonic acid(JA)signaling molecules,which can enhance the activity of HMGR and DXR,and increased the volatile oil content in A.macrocephala.By comparing with the interaction of "ALEB7B-A.lancea",we found that ALEB7 B can induce GA production both in A.macrocephala and A.lancea,while other signal molecules are different.In conclusion,by treating endophytic bacteria and trans-species host as models,this study analyzed the signal mechanism and interaction of endophytic bacteria and volatile oil accumulation of Atractylodes,providing a theoretical basis for the application of endophytic bacteria in the same genus and reference for the artificial cultivation of high quality herbs,paving the way for uncovereing the interactions between endophytes-plants and connections between herb authenticity and microbial assembly. |
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