title: Induction of localized auxin response during spontaneous nodule development in Lotus japonicus.
abstract: In leguminous plants, rhizobial infection of the epidermis triggers proliferation of cortical cells to form a nodule primordium. Recent studies have demonstrated that two classic phytohormones, cytokinin and auxin, have important functions in nodulation. The identification of these functions in Lotus japonicus was facilitated by use of the spontaneous nodule formation 2 (snf2) mutation of the putative cytokinin receptor LOTUS HISTIDINE KINASE 1 (LHK1). Analyses using snf2 demonstrated that constitutive activation of cytokinin signaling causes formation of spontaneous nodule-like structures in the absence of rhizobia and that auxin responses are induced in proliferating cortical cells during such spontaneous nodule development. Thus, cytokinin signaling positively regulates the auxin response. In the present study, we further investigated the induction of the auxin response using a gain-of-function mutation of Ca(2+)/calmodulin-dependent protein kinase (CCaMK) that causes spontaneous nodule formation. We demonstrate that CCaMK(T265D)-mediated spontaneous nodule development is accompanied by a localized auxin response. Thus, a localized auxin response at the site of an incipient nodule primordium is essential for nodule organogenesis.
authors.affiliation: Division of Symbiotic Systems; National Institute for Basic Biology; Aichi, Japan; Department of Basic Biology; School of Life Science; Graduate University for Advanced Studies (SOKENDAI); Aichi, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Suzaki
authors.forename: Momoyo
authors.initials: M
authors.lastname: Ito
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kawaguchi
mesh_terms: D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D003583:Cytokinins / Q000235:genetics / Q000378:metabolism*; D017343:Genes, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D000070116:Lotus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000382:microbiology; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D055170:Plant Root Nodulation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D012231:Rhizobium; D053204:Root Nodules, Plant / Q000254:growth & development*; D015398:Signal Transduction; D013559:Symbiosis
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D010940:Plant Proteins; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases
keywords: CCaMK; Lotus japonicus; auxin; nodulation; spontaneous nodule formation