Reductionist approaches to explore plant microbiota functions
P. SCHULZE-LEFERT (1), R. Zgadzay (2), R. Garrido-Oter (2), S. Hacquard (2), P. Duran (2), S. Spaepen (2), T. Thiergart (2), Y. Bai (2), R. Nakano (2), M. Hashimoto (2), A. Hassani (2), S. Radutiou (3) (1) Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Germany; (2) Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Germany; (3) Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, Denmark, Denmark

We established Arabidopsis leaf- and root-derived microbiota culture collections representing the majority of bacterial species that are reproducibly detectable by culture-independent community sequencing. Using defined bacterial communities and a gnotobiotic Arabidopsis plant system we have shown that the isolates form assemblies resembling natural microbiota on their cognate host organs, but are also capable of ectopic leaf or root colonization (Bai et al., Nature 2015). We have now extended this work to the legume Lotus japonicus, a model for studies on the binary symbiotic relationship with nitrogen-fixing rhizobia inside root nodules. Using community profiling of 16S rRNA gene amplicons we reveal in wild-type L. japonicus distinctive nodule- and root-inhabiting bacterial assemblages that are established by parallel rather than consecutive selection from the soil-borne bacterial community surrounding roots, called the rhizosphere. Comparative analyses of Lotus wild-type and symbiotic mutant plants nfr5, nin1 and lhk1, identified a previously unsuspected role of the nodulation pathway in the establishment of distinctive bacterial assemblages in root and rhizosphere compartments. We found that the loss of nitrogen-fixing symbiosis dramatically alters community structure with contrasting trends in the root and rhizosphere, affecting at least 14 bacterial orders. Our genetic analysis demonstrates a role of the Lotus nodulation pathway beyond the accommodation of nitrogen-fixing rhizobia for the enrichment of a broad taxonomic range of root-inhabiting microbiota members with presumed functions in plant growth promotion and ecological performance.


Abstract Number: P3-3
Session Type: Plenary