A mutant-based analysis of the establishment of Nod-independent symbiosis in the legume Aeschynomene evenia

Quilbé Johan, Nouwen Nico, Pervent Marjorie, Guyonnet Rémi, Cullimore julie, Gressent Frédéric, Horta Araújo Natasha, Gully Djamel, Klopp Christophe, Giraud Eric, Arrighi Jean-François. 2022. A mutant-based analysis of the establishment of Nod-independent symbiosis in the legume Aeschynomene evenia. Plant Physiology, 190 (2) : 1400-1417.

Résumé : Intensive research on nitrogen-fixing symbiosis in two model legumes has uncovered the molecular mechanisms, whereby rhizobial Nod factors activate a plant symbiotic signaling pathway that controls infection and nodule organogenesis. In contrast, the so-called Nod-independent symbiosis found between Aeschynomene evenia and photosynthetic bradyrhizobia, which does not involve Nod factor recognition nor infection thread formation, is less well known. To gain knowledge on how Nod-independent symbiosis is established, we conducted a phenotypic and molecular characterization of A. evenia lines carrying mutations in different nodulation genes. Besides investigating the effect of the mutations on rhizobial symbiosis, we examined their consequences on mycorrhizal symbiosis and in nonsymbiotic conditions. Analyzing allelic mutant series for AePOLLUX, Ca2+/calmodulin dependent kinase, AeCYCLOPS, nodulation signaling pathway 2 (AeNSP2), and nodule inception demonstrated that these genes intervene at several stages of intercellular infection and during bacterial accommodation. We provide evidence that AeNSP2 has an additional nitrogen-dependent regulatory function in the formation of axillary root hairs at lateral root bases, which are rhizobia-colonized infection sites. Our investigation of the recently discovered symbiotic actor cysteine-rich receptor-like kinase specified that it is not involved in mycorrhization; however, it is essential for both symbiotic signaling and early infection during nodulation. These findings provide important insights on the modus operandi of Nod-independent symbiosis and contribute to the general understanding of how rhizobial–legume symbioses are established by complementing the information acquired in model legumes.

Mots-clés Agrovoc : symbiose, Aeschynomene, nodosité racinaire, Fixation de l'azote, formation de nodosités, bactérie fixatrice de l'azote, légumineuse, Rhizobium, Bradyrhizobium

Agences de financement hors UE : Agence Nationale de la Recherche

Projets sur financement : (FRA) Une nouvelle voie symbiotique pour l'infection rhizobienne et la nodulation chez les légumineuses, (FRA) Génétique de la légumineuse Nod-indépendante Aeschynomene evenia pour étudier l'évolution de la symbiose rhizobienne et dans la perspective du transfert de la fixation d'azote aux plantes d'intérêt agronomique

Auteurs et affiliations

• Quilbé Johan, IRD (FRA)
• Nouwen Nico, IRD (FRA)
• Pervent Marjorie, IRD (FRA)
• Guyonnet Rémi, CIRAD-BIOS-UMR LSTM (FRA)
• Cullimore julie, INRAE (FRA)
• Gressent Frédéric, IRD (FRA)
• Horta Araújo Natasha, Université de Montpellier (FRA)
• Gully Djamel, IRD (FRA)
• Klopp Christophe, INRAE (FRA)
• Giraud Eric, IRD (FRA)
• Arrighi Jean-François, IRD (FRA) - auteur correspondant

Source : Cirad-Agritrop (https://agritrop.cirad.fr/614259/)

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