A peptidoglycan-remodeling enzyme is critical for bacteroid differentiation in Bradyrhizobium spp. during legume symbiosis

Gully Djamel, Gargani Daniel, Bonaldi Katia, Grangeteau Cédric, Chaintreuil Clémence, Fardoux Joël, Nguyen Phuong, Marchetti Roberta, Nouwen Nico, Molinaro Antonio, Mergaet Peter, Giraud Eric. 2016. A peptidoglycan-remodeling enzyme is critical for bacteroid differentiation in Bradyrhizobium spp. during legume symbiosis. Molecular Plant-Microbe Interactions, 29 (6) : 447-457.

Quartile : Q1, Sujet : PLANT SCIENCES / Quartile : Q1, Sujet : BIOTECHNOLOGY & APPLIED MICROBIOLOGY / Quartile : Q1, Sujet : BIOCHEMISTRY & MOLECULAR BIOLOGY

Résumé : In response to the presence of compatible rhizobium bacteria, legumes form symbiotic organs called nodules on their roots. These nodules house nitrogen-fixing bacteroids that are a differentiated form of the rhizobium bacteria. In some le- gumes, the bacteroid differentiation comprises a dramatic cell enlargement, polyploidization, and other morphological changes. Here, we demonstrate that a peptidoglycan-modifying enzyme in Bradyrhizobium strains, a DD-carboxypeptidase that contains a peptidoglycan-binding SPOR domain, is essential for normal bacteroid differentiation in Aeschynomene species. The corre- sponding mutants formed bacteroids that are malformed and hypertrophied. However, in soybean, a plant that does not induce morphological differentiation of its symbiont, the mutation does not affect the bacteroids. Remarkably, the mutation also leads to necrosis in a large fraction of the Aeschynomene nodules, in- dicating that a normally formed peptidoglycan layer is essential for avoiding the induction of plant immune responses by the invading bacteria. In addition to exopolysaccharides, capsular polysaccharides, and lipopolysaccharides, whose role during symbiosis is well defined, our work demonstrates an essential role in symbiosis for yet another rhizobial envelope component, the peptidoglycan layer.

Mots-clés Agrovoc : symbiose, Bradyrhizobium, enzyme, Bacteroides, différenciation cellulaire, mutation, peptidase, polyploïdie, code génétique, photosynthèse, nodosité racinaire

Classification Agris : P34 - Biologie du sol
F60 - Physiologie et biochimie végétale

Champ stratégique Cirad : Axe 1 (2014-2018) - Agriculture écologiquement intensive

Auteurs et affiliations

• Gully Djamel, IRD (FRA)
• Gargani Daniel, CIRAD-BIOS-UMR BGPI (FRA)
• Bonaldi Katia, UC (USA)
• Grangeteau Cédric, AgroSup Dijon (FRA)
• Chaintreuil Clémence, IRD (FRA)
• Fardoux Joël, IRD (FRA)
• Nguyen Phuong, IRD (FRA)
• Marchetti Roberta, Université de Naples 2 (FRA)
• Nouwen Nico, IRD (FRA)
• Molinaro Antonio, Université de Naples 2 (ITA)
• Mergaet Peter, CNRS (FRA)
• Giraud Eric, IRD (FRA)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/581702/)

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