MtHAP2-1 is a key transcriptional regulator of symbiotic nodule development regulated by microRNA169 in Medicago truncatula

  1. Jean-Philippe Combier1,
  2. Florian Frugier2,
  3. Françoise de Billy1,
  4. Adnane Boualem2,
  5. Fikri El-Yahyaoui1,
  6. Sandra Moreau1,
  7. Tatiana Vernié1,
  8. Thomas Ott1,
  9. Pascal Gamas1,
  10. Martin Crespi2,4, and
  11. Andreas Niebel1,3
  1. 1 LIPM (Laboratoire des Interactions Plantes-Microorganismes) INRA-CNRS (Institut de National de la Recherche-Centre national de la recherche scientifique), 31326 Castanet-Tolosan, France;
  2. 2 ISV (Institut des Sciences du Végétal), CNRS, 91198 Gif sur Yvette, France

Abstract

In the model legume Medicago truncatula, we identified a new transcription factor of the CCAAT-binding family, MtHAP2-1, for which RNA interference (RNAi) and in situ hybridization experiments indicate a key role during nodule development, possibly by controlling nodule meristem function. We could also show that MtHAP2-1 is regulated by microRNA169, whose overexpression leads to the same nodule developmental block as MtHAP2-1 RNAi constructs. The complementary expression pattern of miR169 and MtHAP2-1 and the phenotype of miR169-resistant MtHAP2-1 nodules strongly suggest, in addition, that the miR169-mediated restriction of MtHAP2-1 expression to the nodule meristematic zone is essential for the differentiation of nodule cells.

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