A novel RNA-binding peptide regulates the establishment of the Medicago truncatula-Sinorhizobium meliloti nitrogen-fixing symbiosis

Plant J. 2010 Apr 1;62(1):24-38. doi: 10.1111/j.1365-313X.2009.04121.x. Epub 2009 Dec 23.


Plants use a variety of small peptides for cell to cell communication during growth and development. Leguminous plants are characterized by their ability to develop nitrogen-fixing nodules via an interaction with symbiotic bacteria. During nodule organogenesis, several so-called nodulin genes are induced, including large families that encode small peptides. Using a three-hybrid approach in yeast cells, we identified two new small nodulins, MtSNARP1 and MtSNARP2 (for small nodulin acidic RNA-binding protein), which interact with the RNA of MtENOD40, an early induced nodulin gene showing conserved RNA secondary structures. The SNARPs are acidic peptides showing single-stranded RNA-binding activity in vitro and are encoded by a small gene family in Medicago truncatula. These peptides exhibit two new conserved motifs and a putative signal peptide that redirects a GFP fusion to the endoplasmic reticulum both in protoplasts and during symbiosis, suggesting they are secreted. MtSNARP2 is expressed in the differentiating region of the nodule together with several early nodulin genes. MtSNARP2 RNA interference (RNAi) transgenic roots showed aberrant early senescent nodules where differentiated bacteroids degenerate rapidly. Hence, a functional symbiotic interaction may be regulated by secreted RNA-binding peptides.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Gene Expression Regulation, Plant
  • Medicago truncatula / genetics*
  • Medicago truncatula / microbiology
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Nucleic Acid Conformation
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Plant Root Nodulation
  • Plants, Genetically Modified / genetics
  • Plants, Genetically Modified / microbiology
  • Protein Sorting Signals
  • RNA Interference
  • RNA, Plant / genetics
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Sequence Alignment
  • Sinorhizobium meliloti / physiology*
  • Symbiosis / genetics*


  • Membrane Proteins
  • Plant Proteins
  • Protein Sorting Signals
  • RNA, Plant
  • RNA-Binding Proteins
  • nodulin