Teulet A. auteur aut IRD Busset N. auteur aut IRD Fardoux Joël auteur aut IRD Gully Djamel auteur aut IRD Chaintreuil Clémence auteur aut IRD Cartieaux Fabienne auteur aut IRD Jauneau A. auteur aut IRD Comorge V. auteur aut IRD Okazaki S. auteur aut IRD Kaneko T. auteur aut IRD Gressent F. auteur aut IRD Nouwen Nico auteur aut IRD Arrighi Jean-François auteur aut IRD Koebnik Ralf auteur aut IRD Mergaert P. auteur aut IRD Deslandes L. auteur aut IRD Giraud Eric auteur aut IRD text journalArticle eng text/pdf reformatted digital access Several Bradyrhizobium species nodulate the leguminous plant Aeschynomene indica in a type III secretion system-dependent manner, independently of Nod factors. To date, the underlying molecular determinants involved in this symbiotic process remain unknown. To identify the rhizobial effectors involved in nodulation, we mutated 23 out of the 27 effector genes predicted in Bradyrhizobium strain ORS3257. The mutation of nopAO increased nodulation and nitrogenase activity, whereas mutation of 5 other effector genes led to various symbiotic defects. The nopM1 and nopP1 mutants induced a reduced number of nodules, some of which displayed large necrotic zones. The nopT and nopAB mutants induced uninfected nodules, and a mutant in a yet-undescribed effector gene lost the capacity for nodule formation. This effector gene, widely conserved among bradyrhizobia, was named ernA for "effector required for nodulation-A." Remarkably, expressing ernA in a strain unable to nodulate A. indica conferred nodulation ability. Upon its delivery by Pseudomonas fluorescens into plant cells, ErnA was specifically targeted to the nucleus, and a fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy approach supports the possibility that ErnA binds nucleic acids in the plant nuclei. Ectopic expression of ernA in A. indica roots activated organogenesis of root- and nodule-like structures. Collectively, this study unravels the symbiotic functions of rhizobial type III effectors playing distinct and complementary roles in suppression of host immune functions, infection, and nodule organogenesis, and suggests that ErnA triggers organ development in plants by a mechanism that remains to be elucidated. specialized Bradyrhizobium T3SS symbiosis nodulation legume 076 084 116 43 21758-21768 2019 0027-8424 https://www.documentation.ird.fr/hor/fdi:010077167 10.1073/pnas.1904456116 0027-8424 [F B010077167] https://www.documentation.ird.fr/hor/fdi:010077167 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers19-11/010077167.pdf IRD - Base Horizon / Pleins textes 2019-12-12 2025-02-24 fdi:010077167 fre