title: Two CCAAT-box-binding transcription factors redundantly regulate early steps of the legume-rhizobia endosymbiosis.
abstract: During endosymbiotic interactions between legume plants and nitrogen-fixing rhizobia, successful root infection by bacteria and nodule organogenesis requires the perception and transduction of bacterial lipo-chitooligosaccharidic signal called Nod factor (NF). NF perception in legume roots leads to the activation of an early signaling pathway and of a set of symbiotic genes which is controlled by specific early transcription factors (TFs) including CYCLOPS/IPD3, NSP1, NSP2, ERN1 and NIN. In this study, we bring convincing evidence that the Medicago truncatula CCAAT-box-binding NF-YA1 TF, previously associated with later stages of rhizobial infection and nodule meristem formation is, together with its closest homolog NF-YA2, also an essential positive regulator of the NF-signaling pathway. Here we show that NF-YA1 and NF-YA2 are both expressed in epidermal cells responding to NFs and their knock-down by reverse genetic approaches severely affects the NF-induced expression of symbiotic genes and rhizobial infection. Further over-expression, transactivation and ChIP-PCR approaches indicate that NF-YA1 and NF-YA2 function, at least in part, via the direct activation of ERN1. We thus propose a model in which NF-YA1 and NF-YA2 appear as early symbiotic regulators acting downstream of DMI3 and NIN and possibly within the same regulatory complexes as NSP1/2 to directly activate the expression of ERN1.
authors.affiliation: Laboratoire des Interactions Plantes-Microorganismes (LIPM), INRA, UMR441, F-31326, Castanet-Tolosan, France; Laboratoire des Interactions Plantes-Microorganismes (LIPM), CNRS, UMR2594, F-31326, Castanet-Tolosan, France.
authors.forename: Tom
authors.initials: T
authors.lastname: Laloum
authors.forename: Maël
authors.initials: M
authors.lastname: Baudin
authors.forename: Lisa
authors.initials: L
authors.lastname: Frances
authors.forename: Agnes
authors.initials: A
authors.lastname: Lepage
authors.forename: Benjamin
authors.initials: B
authors.lastname: Billault-Penneteau
authors.forename: Marion R
authors.initials: MR
authors.lastname: Cerri
authors.forename: Federico
authors.initials: F
authors.lastname: Ariel
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Jardinaud
authors.forename: Pascal
authors.initials: P
authors.lastname: Gamas
authors.forename: Fernanda
authors.initials: F
authors.lastname: de Carvalho-Niebel
authors.forename: Andreas
authors.initials: A
authors.lastname: Niebel
mesh_terms: D023081:CCAAT-Binding Factor / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D046913:Medicago truncatula / Q000166:cytology / Q000235:genetics* / Q000382:microbiology / Q000502:physiology; D042282:Microdissection; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D018749:RNA, Plant / Q000737:chemistry / Q000235:genetics; D053204:Root Nodules, Plant / Q000166:cytology / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D017423:Sequence Analysis, RNA; D015398:Signal Transduction; D016962:Sinorhizobium meliloti / Q000502:physiology*; D013559:Symbiosis; D014026:Nicotiana / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D023081:CCAAT-Binding Factor; D010940:Plant Proteins; D018749:RNA, Plant; D014157:Transcription Factors
keywords: CCAAT box-binding factor; Medicago truncatula; Nod factor signaling; legume-rhizobium symbiosis; nuclear factor Y; transcription factor