title: KNAT3/4/5-like class 2 KNOX transcription factors are involved in Medicago truncatula symbiotic nodule organ development.
abstract: We investigated the role of KNOX genes in legume root nodule organogenesis. Class 1 KNOX homeodomain transcription factors (TFs) are involved in plant shoot development and leaf shape diversity. Class 2 KNOX genes are less characterized, even though an antagonistic function relative to class 1 KNOXs was recently proposed. In silico expression data and further experimental validation identified in the Medicago truncatula model legume three class 2 KNOX genes, belonging to the KNAT3/4/5-like subclass (Mt KNAT3/4/5-like), as expressed during nodulation from early stages. RNA interference (RNAi)-mediated silencing and overexpression studies were used to unravel a function for KNOX TFs in nodule development. Mt KNAT3/4/5-like genes encoded four highly homologous proteins showing overlapping expression patterns during nodule organogenesis, suggesting functional redundancy. Simultaneous reduction of Mt KNAT3/4/5-like genes indeed led to an increased formation of fused nodule organs, and decreased the expression of the MtEFD (Ethylene response Factor required for nodule Differentiation) TF and its direct target MtRR4, a cytokinin response gene. Class 2 KNOX TFs therefore regulate legume nodule development, potentially through the MtEFD/MtRR4 cytokinin-related regulatory module, and may control nodule organ boundaries and shape like class 2 KNOX function in leaf development.
authors: Istituto di Biologia e Biotecnologia Agraria (IBBA), Operative Unit of Rome, Consiglio Nazionale delle Ricerche (CNR), Via Salaria Km. 29300-00015, Monterotondo Scalo (Roma), Italy.
authors: Elisabetta
authors: E
authors: Di Giacomo
authors: Institute of Plant Sciences - Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, Gif sur Yvette, 91190, France.
authors: Carole
authors: C
authors: Laffont
authors: Istituto di Biologia e Biotecnologia Agraria (IBBA), Operative Unit of Rome, Consiglio Nazionale delle Ricerche (CNR), Via Salaria Km. 29300-00015, Monterotondo Scalo (Roma), Italy.
authors: Francesca
authors: F
authors: Sciarra
authors: Istituto di Biologia e Biotecnologia Agraria (IBBA), Operative Unit of Rome, Consiglio Nazionale delle Ricerche (CNR), Via Salaria Km. 29300-00015, Monterotondo Scalo (Roma), Italy.
authors: Maria Adelaide
authors: MA
authors: Iannelli
authors: Institute of Plant Sciences - Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, Gif sur Yvette, 91190, France.
authors: Florian
authors: F
authors: Frugier
authors: Istituto di Biologia e Biotecnologia Agraria (IBBA), Operative Unit of Rome, Consiglio Nazionale delle Ricerche (CNR), Via Salaria Km. 29300-00015, Monterotondo Scalo (Roma), Italy.
authors: Giovanna
authors: G
authors: Frugis
mesh_terms: D018533:Biomass; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D046913:Medicago truncatula / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D008954:Models, Biological; D038081:Organogenesis / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000378:metabolism*; D055170:Plant Root Nodulation / Q000235:genetics; D018520:Plant Shoots / Q000254:growth & development; D053204:Root Nodules, Plant / Q000254:growth & development* / Q000378:metabolism*; D013559:Symbiosis / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors
keywords: 
  EFD
  ; 
  KNOX
  ; 
  Medicago truncatula
  ; cytokinin; homeobox; nodule; organogenesis; root