title: The structure of the culturable root bacterial endophyte community of Nicotiana attenuata is organized by soil composition and host plant ethylene production and perception.
abstract: *A plant's bacterial endophyte community is thought to be recruited from the rhizosphere, but how this recruitment is influenced by the plant's phytohormone signaling is unknown. Ethylene regulates plant-microbe interactions; here, we assess the role of ethylene in the recruitment of culturable endophytic bacteria from native soils. *We grew wild-type Nicotiana attenuata plants and isogenic transformed plants deficient in ethylene biosynthesis (ir-aco1) or perception (35S-etr1) in four native soils and quantified the extent of culturable bacterial endophyte colonization (by plate counting) and diversity (by amplified rDNA restriction analysis and 16S rDNA sequencing). *The endophyte community composition was influenced by soil type and ethylene signaling. Plants grown in organic (vs mineral) soils harbored a more diverse community and plants impaired in ethylene homeostasis harbored a less diverse community than wild-type plants. Wild-type and ethylene signaling-impaired plants fostered distinct bacteria in addition to common ones. In vitro re-colonization by common and genotype-specific isolates demonstrated the specificity of some associations and the susceptibility of 35S-etr1 seedlings to all tested bacterial isolates, suggesting an active process of colonization driven by plant- and microbe-specific genes. *We propose that soil composition and ethylene homeostasis play central roles in structuring the bacterial endophyte community in N. attenuata roots.
authors.affiliation: Max Planck Institute for Chemical Ecology, Hans-Knoell-Str. 8, 07745 Jena, Germany.
authors.forename: Hoang Hoa
authors.initials: HH
authors.lastname: Long
authors.forename: Dorothea G
authors.initials: DG
authors.lastname: Sonntag
authors.forename: Dominik D
authors.initials: DD
authors.lastname: Schmidt
authors.forename: Ian T
authors.initials: IT
authors.lastname: Baldwin
mesh_terms: D001419:Bacteria / Q000235:genetics*; D044822:Biodiversity; D015169:Colony Count, Microbial; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D017753:Ecosystem; D005030:Ethylenes / Q000096:biosynthesis*; D005838:Genotype; D038821:Mycorrhizae / Q000235:genetics / Q000378:metabolism; D010937:Plant Growth Regulators; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology*; D030821:Plants, Genetically Modified; D012336:RNA, Ribosomal, 16S; D036226:Seedlings / Q000502:physiology; D015398:Signal Transduction; D012987:Soil / Q000032:analysis*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D005030:Ethylenes; D010937:Plant Growth Regulators; D012336:RNA, Ribosomal, 16S; D012987:Soil; C036216:ethylene