Journal Article

Rhizobium-legume symbiosis in the absence of Nod factors: two possible scenarios with or without the T3SS

Teulet, Albin, Suranaree University of Technology (SUT), Gully, Djamel, Okazaki, Shin, Chaintreuil, Clémence, Tokyo University of Agriculture and Technology (TUAT), Laboratoire des symbioses tropicales et méditerranéennes (UMR LSTM) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université Montpellier 1 (UM1)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Nouwen, Nico, French national research agency [ANR-BugsInaCell-13-BSV7-0013]; Franco-Thai PHC Siam program (project SIAM) [29589XA], Fardoux, Joel, Yasuda, Michiko, Miwa, Hiroki, Arrighi, Jean-François, ANR-13-BSV7-0013,BugsInACell,Accommodation intracellulaire des bactéries symbiotiques fixatrices d'azote, Tittabutr, Panlada, Teaumroong, Neung, Furuta, Noriyuki, Giraud, Eric, Thouin, Julien

2016

Overview

The occurrence of alternative Nod factor (NF)-independent symbiosis between legumes and rhizobia was first demonstrated in some Aeschynomene species that are nodulated by photosynthetic bradyrhizobia lacking the canonical nodABC genes. In this study, we revealed that a large diversity of non-photosynthetic bradyrhizobia, including B. elkanii, was also able to induce nodules on the NF-independent Aeschynomene species, A. indica. Using cytological analysis of the nodules and the nitrogenase enzyme activity as markers, a gradient in the symbiotic interaction between bradyrhizobial strains and A. indica could be distinguished. This ranged from strains that induced nodules that were only infected intercellularly to rhizobial strains that formed nodules in which the host cells were invaded intracellularly and that displayed a weak nitrogenase activity. In all non-photosynthetic bradyrhizobia, the type III secretion system (T3SS) appears required to trigger nodule organogenesis. In contrast, genome sequence analysis revealed that apart from a few exceptions, like the Bradyrhizobium ORS285 strain, photosynthetic bradyrhizobia strains lack a T3SS. Furthermore, analysis of the symbiotic properties of an ORS285 T3SS mutant revealed that the T3SS could have a positive or negative role for the interaction with NF-dependent Aeschynomene species, but that it is dispensable for the interaction with all NF-independent Aeschynomene species tested. Taken together, these data indicate that two NF-independent symbiotic processes are possible between legumes and rhizobia: one dependent on a T3SS and one using a so far unknown mechanism.

• Publisher: Nature Publishing Group,CCSD,Nature Publishing Group UK,Oxford University Press
• Subject: 631/326/171/1818 / Aeschynomene / Bacteria / Biological Evolution / Biomedical and Life Sciences / Bradyrhizobium / Bradyrhizobium - classification / Bradyrhizobium - genetics / Bradyrhizobium - metabolism / DNA, Bacterial - analysis / Ecology / Enzymatic activity / Enzyme activity / Evolutionary Biology / Fabaceae - microbiology / Genome, Bacterial / Genomic analysis / Legumes / Life Sciences / Microbial Ecology / Microbial Genetics and Genomics / Microbiology / Nitrogenase / Nitrogenase - metabolism / Nod factors / Nodules / Nucleotide sequence / Organogenesis / Original / original-article / Photosynthesis / Phylogeny / Polymerase Chain Reaction / RNA, Ribosomal, 16S - analysis / Sequence analysis / Sequence Analysis, DNA / Symbiosis / Symbiosis - genetics
• ISBN: 0003666713000