title: Consequences of antagonistic interactions between endophytic fungus and bacterium on plant growth and defense responses in Atractylodes lancea.
abstract: Many studies have examined pair-wise interactions between plants and endophytes, while overlooking the interplays among multiple endosymbionts and their combined impacts on hosts. In this study, Atractylodes lancea plantlets were inoculated with endophytic fungus Acremonium strictum AL16, or endophytic bacterium Acinetobacter sp., or both, to investigate the impacts of the three-way symbiosis on the host. Our results showed that defense-related responses of the co-inoculated plantlets were delayed and weakened relative to plantlets with single inoculants, but no detrimental effects on phyto-physiology (growth, photosynthesis) were observed after combined inoculations. Quantitative PCR analysis verified a decrease in AL16 colonization density within plants after co-inoculation with the endobacteria. An in vitro assay was then performed to elucidate the suppressed plant defense responses and reduced fungal colonization by dual inoculation. The data showed that the presence of Acinetobacter sp. reduced AL16 colony diameter and spore germination rate without negatively affecting fungal morphology. Additionally, direct hyphal attachment of the bacterium to AL16 in vitro was visualized by scanning electronic microscopy. Therefore, we propose that a balanced and compatible symbiosis might require constraints conferred by the antagonistic endophyte Acinetobacter sp. on the fungus AL16 in the tripartite endophytic bacterium-fungus-plant system.
authors.affiliation: Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Sciences, Nanjing Normal University, Nanjing, China.
authors.forename: Xiao-Mi
authors.initials: XM
authors.lastname: Wang
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Teng
authors.initials: T
authors.lastname: Yang
authors.forename: Cheng-Gang
authors.initials: CG
authors.lastname: Ren
authors.forename: Hai-Lin
authors.initials: HL
authors.lastname: Zheng
authors.forename: Chuan-Chao
authors.initials: CC
authors.lastname: Dai
mesh_terms: D000150:Acinetobacter / Q000254:growth & development / Q000502:physiology*; D000164:Acremonium / Q000502:physiology*; D031174:Atractylodes / Q000276:immunology / Q000382:microbiology* / Q000502:physiology*; D001422:Bacterial Adhesion; D015169:Colony Count, Microbial; D060026:Endophytes / Q000254:growth & development / Q000502:physiology*; D008855:Microscopy, Electron, Scanning; D010788:Photosynthesis; D063245:Plant Development; D060888:Real-Time Polymerase Chain Reaction; D013559:Symbiosis
keywords: Acinetobacter sp.; Acremonium strictum; Anti-fungus; Atractylodes lancea; Bacterial attachment; Defense responses; Endophytes