Legume-rhizobia interaction; from simple to complex associations. Simona Radutoiu Aarhus University, Department of Molecular Biology and Genetics

Transcription

1 Legume-rhizobia interaction; from simple to complex associations Simona Radutoiu Aarhus University, Department of Molecular Biology and Genetics

2 Nitrogen-fixing symbiosis in root nodules

3 Nitrogen-fixing symbiosis in root nodules

4 Nitrogen-fixing symbiosis in root nodules allows legumes to grow on nitrogen poor soils

5 Legumes select the nodule-infecting rhizobia not on the basis of their nitrogen-fixing ability H 2 C Nod factor (LCO) O H O O H O O C N C H 3 N H 2 O C C H 2 O H O C H 2 O H O O C N H C H 3 O 3 H 3 C C O H 3 C O O H H O O H 2 C O O H N H O H O C C H 3 O Nodule and Infection thread formation ( H 2 C ) 8 C H C H ( H 2 C ) 5 C H 3 NFR1/NFR5 Mesorhizobium lotilacz infection of nodule in Lotus japonicus

6 The plant root symbioses Root symbionts Arbuscular mycorrhizal (AM) fungi Nitrogen-fixing bacteria (Rhizobia) Philippot et al. 2013, Nature Reviews Microbiology

7 M. loti R7A GFP + KAW12 DsRed Endophytes can use the M.loti-induced infection threads to infect the nodule Zgadzaj et al., 2015

8 M. loti exou -GFP M. loti exou-gfp + Kaw12-DsRed 87 of 3653 nodules (2.4%) 510 of 3588 nodules (14%)*** Kaw12 endophyte promotes nodule infection by the less efficient, but nitrogen fixing M.loti exou

9 Nitrogen-fixing symbiosis in root nodules allows legumes to grow on nitrogen poor soils

10 REDUCTIONIST APPROACH Lotus japonicus Mesorhizobium loti (GENERALIST) APPROACH Lotus japonicus soil microbiota

11 nodule rhizosphere soil root Distinct bacterial communities assemble at the Lotus japonicus root-soil interface Zgadzaj & Garrido-Oter, PNAS 2016

12 12 OTUs enriched in nodules of which 7 OTUs- Rhizobiales 6 OTUs - Mesorhizobium Nodules host a highly selective bacterial community Zgadzaj & Garrido-Oter, PNAS 2016

13 Is nitrogen-fixing symbiosis influencing the associated microbiota? WT lhk1-1 nfr5-2 nin2 wt nfr1/nfr5 Zgadzaj & Garrido-Oter, PNAS 2016

14 Actinobacteridae, Rhodospirilalles, Sphingobacteriales and Xanthomonadales Burkholderiales Flavobacteriales, Myxococcales, Pseudomonadales, and Sphingomonadales Differentiation of root microbiota across multiple bacterial orders is affected Zgadzaj & Garrido-Oter, PNAS 2016

15 Rhizobiales Enrichment of Rhizobiales in root and rhizosphere depends on the symbiotic pathway

16 Native soil Native soil + 10mM KNO3 Nitrogen-fixing symbiosis promotes association with specific soil bacteria that promote plant growth

17 Nitrogen-fixing symbiosis in root nodules has major consequences for interactions in the microbial communities Soil

18 Nitrogen-fixing symbiosis in root nodules has major consequences for interactions in the microbial communities Symbiosis

19 ? Test conditions Soil conditions

20 REDUCTIONIST APPROACH Lotus japonicus Mesorhizobium loti (GENERALIST) APPROACH Lotus japonicus soil microbiota

21 CARB Centre Anna Malolepszy Simon Kelly Christina Grossmann Niels Sandal Mick Blaise Kasper Andersen Stig Andersen Yosuke Umehara Keisuke Yokota Acknowledgments Paul Schulze-Lefert, MPI, Germany Rafal Zgadzaj Ruben Garrido-Oter Clive Ronson- Otago University, New Zealand Euan James- James Hutton Institute, UK

22

23 E to K Chitinase E 159 to K Chitinase WT An enzymatically active Chitinase is required for a functional root-nodule symbiosis

24 chitinase mutants: no signs of plant defense reaction chitinase mutants: no transcriptional activation of defense genes nm acetylene/root/hour 0,2 0,15 0,1 0,05 0 Mutants at Sym43 locus are defective for nitrogen fixation

25 WT WT WT sym4 3 sym4 3 sym4 3 R7A R7AΔnolL R7AΔnodZ M.loti Wt nodz noll Wt sym43 Wild-type- Gifu chitinase mutants are rescued by M.loti noll or nodz

26 REDUCTIONIST APPROACH Lotus japonicus Mesorhizobium loti (GENERALIST) APPROACH Lotus japonicus soil microbiota Symbiotic nitrogen fixation binary interaction to Symbiotic nitrogen fixation community interaction

27 How diverse is the bacterial community associated with Lotus japonicus grown in soil? Cooperative work with Paul Schulze-Lefert nodule root 454 Sequencing of 16S rrna amplicons

28 Root and rhizosphere bacterial communities are altered in the absence of nitrogen-fixation

29 Lotus plants grown in Cologne soil Rhizobiales Nodules host a distinct but not restrictive bacterial community

30 1. Epidermal events leading to rhizobial infection 2. Cortical events controlling nodule infection by rhizobia and the onset of nitrogen fixation Desbrosses, Rhizobial infection consequences for the root-associated microbiota

31 The plant root microbiome AM symbiosis Philippot et al. 2013, Nature Reviews Microbiology

32

33 root nodule soil rhizosphere

34 The Nod-Factor (LCO)

35 Symbiosis with rhizobia Flavonoids Rhizobia Nod-Factor

36 Legume-Rhizobia symbiosis integrated in the complex plant-microbiota interaction

37 Specificity for nodulation vs. specificity for infection

38 KAW12 colonised nodules of total nodules - frequency M. loti-gfp + KAW12 DsRed 8% M. loti exou-gfp + KAW12 DsRed 33% M. loti exou-gfp + KAW12 eps PssN-DsRed 0% KAW12 EPS are required for endophytic colonisation of Lotus nodules