title: Different cytokinin histidine kinase receptors regulate nodule initiation as well as later nodule developmental stages in Medicago truncatula.
abstract: Legume plants adapt to low nitrogen by developing an endosymbiosis with nitrogen-fixing soil bacteria to form a new specific organ: the nitrogen-fixing nodule. In the Medicago truncatula model legume, the MtCRE1 cytokinin receptor is essential for this symbiotic interaction. As three other putative CHASE-domain containing histidine kinase (CHK) cytokinin receptors exist in M. truncatula, we determined their potential contribution to this symbiotic interaction. The four CHKs have extensive redundant expression patterns at early nodulation stages but diverge in differentiated nodules, even though MtCHK1/MtCRE1 has the strongest expression at all stages. Mutant and knock-down analyses revealed that other CHKs than MtCHK1/CRE1 are positively involved in nodule initiation, which explains the delayed nodulation phenotype of the chk1/cre1 mutant. In addition, cre1 nodules exhibit an increased growth, whereas other chk mutants have no detectable phenotype, and the maintained nitrogen fixation capacity in cre1 requires other CHK genes. Interestingly, an AHK4/CRE1 genomic locus from the aposymbiotic Arabidopsis plant rescues nodule initiation but not the nitrogen fixation capacity. This indicates that different CHK cytokinin signalling pathways regulate not only nodule initiation but also later developmental stages, and that legume-specific determinants encoded by the MtCRE1 gene are required for later nodulation stages than initiation.
authors.affiliation: Institute of Plant Sciences-Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, 91190, Gif-sur-Yvette, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Boivin
authors.affiliation: Institute of Plant Sciences-Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, 91190, Gif-sur-Yvette, France.
authors.forename: Théophile
authors.initials: T
authors.lastname: Kazmierczak
authors.affiliation: Institute of Plant Sciences-Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, 91190, Gif-sur-Yvette, France.
authors.forename: Mathias
authors.initials: M
authors.lastname: Brault
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK, USA.
authors.forename: Jiangqi
authors.initials: J
authors.lastname: Wen
authors.affiliation: Laboratoire des Interactions Plantes-Microorganismes (LIPM), Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Gamas
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK, USA.
authors.forename: Kirankumar S
authors.initials: KS
authors.lastname: Mysore
authors.affiliation: Institute of Plant Sciences-Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, 91190, Gif-sur-Yvette, France. florian.frugier@ips2.universite-paris-saclay.fr.
authors.forename: Florian
authors.initials: F
authors.lastname: Frugier
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D003583:Cytokinins / Q000378:metabolism; D018745:Genome, Plant; D046913:Medicago truncatula / Q000378:metabolism / Q000382:microbiology*; D009586:Nitrogen Fixation; D010937:Plant Growth Regulators / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified / Q000382:microbiology; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000502:physiology*; D053204:Root Nodules, Plant / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D015398:Signal Transduction; D020579:Sinorhizobium / Q000502:physiology; D013559:Symbiosis
chemical_list: D003583:Cytokinins; D010937:Plant Growth Regulators; D011956:Receptors, Cell Surface
keywords: AHK4/CRE1; Arabidopsis; Medicago; cyclase/histidine kinase; cytokinin; legume symbiotic nodulation