Transcriptomic dissection of Bradyrhizobium sp. strain ORS285 in symbiosis with Aeschynomene spp. inducing different bacteroid morphotypes with contrasted symbiotic efficiency

Florian Lamouche, Djamel Gully, Anaïs Chaumeret, Nico Nouwen, Camille Verly, Olivier Pierre, Coline Sciallano, Joël Fardoux, Christian Jeudy, Attila Szücs, Samuel Mondy, Christophe Salon, István Nagy, Attila Kereszt, Yves Dessaux, Eric Giraud, Peter Mergaert, Benoit Alunni

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

To circumvent the paucity of nitrogen sources in the soil legume plants establish a symbiotic interaction with nitrogen-fixing soil bacteria called rhizobia. During symbiosis, the plants form root organs called nodules, where bacteria are housed intracellularly and become active nitrogen fixers known as bacteroids. Depending on their host plant, bacteroids can adopt different morphotypes, being either unmodified (U), elongated (E) or spherical (S). E- and S-type bacteroids undergo a terminal differentiation leading to irreversible morphological changes and DNA endoreduplication. Previous studies suggest that differentiated bacteroids display an increased symbiotic efficiency (E > U and S > U). In this study, we used a combination of Aeschynomene species inducing E- or S-type bacteroids in symbiosis with Bradyrhizobium sp. ORS285 to show that S-type bacteroids present a better symbiotic efficiency than E-type bacteroids. We performed a transcriptomic analysis on E- and S-type bacteroids formed by Aeschynomene afraspera and Aeschynomene indica nodules and identified the bacterial functions activated in bacteroids and specific to each bacteroid type. Extending the expression analysis in E- and S-type bacteroids in other Aeschynomene species by qRT-PCR on selected genes from the transcriptome analysis narrowed down the set of bacteroid morphotype-specific genes. Functional analysis of a selected subset of 31 bacteroid-induced or morphotype-specific genes revealed no symbiotic phenotypes in the mutants. This highlights the robustness of the symbiotic program but could also indicate that the bacterial response to the plant environment is partially anticipatory or even maladaptive. Our analysis confirms the correlation between differentiation and efficiency of the bacteroids and provides a framework for the identification of bacterial functions that affect the efficiency of bacteroids.

Original languageEnglish
Pages (from-to)3244-3258
Number of pages15
JournalEnvironmental Microbiology
Volume21
Issue number9
DOIs
Publication statusPublished - Jan 1 2019

    Fingerprint

ASJC Scopus subject areas

  • Microbiology
  • Ecology, Evolution, Behavior and Systematics

Cite this

Lamouche, F., Gully, D., Chaumeret, A., Nouwen, N., Verly, C., Pierre, O., Sciallano, C., Fardoux, J., Jeudy, C., Szücs, A., Mondy, S., Salon, C., Nagy, I., Kereszt, A., Dessaux, Y., Giraud, E., Mergaert, P., & Alunni, B. (2019). Transcriptomic dissection of Bradyrhizobium sp. strain ORS285 in symbiosis with Aeschynomene spp. inducing different bacteroid morphotypes with contrasted symbiotic efficiency. Environmental Microbiology, 21(9), 3244-3258. https://doi.org/10.1111/1462-2920.14292