AP2-ERF transcription factors mediate Nod factor dependent Mt ENOD11 activation in root hairs via a novel cis-regulatory motif

Plant Cell. 2007 Sep;19(9):2866-85. doi: 10.1105/tpc.107.052944. Epub 2007 Sep 7.


Rhizobium Nod factors (NFs) are specific lipochitooligosaccharides that activate host legume signaling pathways essential for initiating the nitrogen-fixing symbiotic association. This study describes the characterization of cis-regulatory elements and trans-interacting factors that regulate NF-dependent and epidermis-specific gene transcription in Medicago truncatula. Detailed analysis of the Mt ENOD11 promoter using deletion, mutation, and gain-of-function constructs has led to the identification of an NF-responsive regulatory unit (the NF box) sufficient to direct NF-elicited expression in root hairs. NF box-mediated expression requires a major GCC-like motif, which is also essential for the binding of root hair-specific nuclear factors. Yeast one-hybrid screening has identified three closely related AP2/ERF transcription factors (ERN1 to ERN3) that are able to bind specifically to the NF box. ERN1 is identical to an ERF-like factor identified recently. Expression analysis has revealed that ERN1 and ERN2 genes are upregulated in root hairs following NF treatment and that this activation requires a functional NFP gene. Transient expression assays in Nicotiana benthamiana have further shown that nucleus-targeted ERN1 and ERN2 factors activate NF box-containing reporters, whereas ERN3 represses ERN1/ERN2-dependent transcription activation. A model is proposed for the fine-tuning of NF-elicited gene transcription in root hairs involving the interplay between repressor and activator ERN factors.

MeSH terms

  • Amino Acid Sequence
  • Base Pairing
  • Base Sequence
  • Cell Nucleus / metabolism
  • Conserved Sequence
  • Gene Expression Regulation, Plant*
  • Genes, Plant
  • Medicago truncatula / genetics*
  • Models, Genetic
  • Molecular Sequence Data
  • Nicotiana / cytology
  • Plant Epidermis / cytology
  • Plant Epidermis / metabolism
  • Plant Proteins / genetics*
  • Plant Proteins / isolation & purification
  • Plant Proteins / metabolism*
  • Plant Roots / genetics*
  • Plant Roots / metabolism
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Transport
  • Regulatory Sequences, Nucleic Acid / genetics*
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcriptional Activation
  • Two-Hybrid System Techniques
  • Up-Regulation


  • ENOD11 protein, Medicago truncatula
  • Plant Proteins
  • Transcription Factors

Associated data

  • GENBANK/EU038802
  • GENBANK/EU038803
  • GENBANK/EU038804