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The Casuarina NIN gene is transcriptionally activated throughout Frankia root infection as well as in response to bacterial diffusible signals

2015; Wiley; Volume: 208; Issue: 3 Linguagem: Inglês

10.1111/nph.13506

1469-8137

Fernando Clavijo-Coppens, Issa Diédhiou, Virginie Vaissayre, Laurent Brottier, Jennifer Acolatse, Daniel Moukouanga, Amandine Crabos, Florence Auguy, Claudine Franche, Hassen Gherbi, Antony Champion, Valérie Hocher, David G. Barker, Didier Bogusz, Louis S. Tisa, Sergio Svistoonoff,

Agronomic Practices and Intercropping Systems

Summary Root nodule symbioses ( RNS ) allow plants to acquire atmospheric nitrogen by establishing an intimate relationship with either rhizobia, the symbionts of legumes or Frankia in the case of actinorhizal plants. In legumes, NIN ( Nodule IN ception) genes encode key transcription factors involved in nodulation. Here we report the characterization of Cg NIN , a NIN gene from the actinorhizal tree Casuarina glauca using both phylogenetic analysis and transgenic plants expressing either Pro Cg NIN ::reporter gene fusions or Cg NIN RNA i constructs. We have found that Cg NIN belongs to the same phylogenetic group as other symbiotic NIN genes and Cg NIN is able to complement a legume nin mutant for the early steps of nodule development. Cg NIN expression is correlated with infection by Frankia , including preinfection stages in developing root hairs, and is induced by culture supernatants. Knockdown mutants were impaired for nodulation and early root hair deformation responses were severely affected. However, no mycorrhizal phenotype was observed and no induction of Cg NIN expression was detected in mycorrhizas. Our results indicate that elements specifically required for nodulation include NIN and possibly related gene networks derived from the nitrate signalling pathways.