miR390 and the TAS3-derived tasiRNAs pathway regulate nodule development and bacterial infection during M. truncatula-S. meliloti symbiosis

HOBECKER, KAREN; REYNOSO, MAURICIO; BUSTOS, PILAR; BLANCO, FLAVIO; CRESPI, MARTÍN AND ZANETTI, MARÍA EUGENIA

Mar del Plata

Congreso; XV Congreso Latinoamericano XXX congreso Argentino de Fisiología Vegetal; 2014

SAFV (Sociedad Argenbtina de Fisiología Vegetal)

The development of nitrogen fixing nodules depends on the activation of two highly coordinated genetic programs in leguminous plants: the nodule organogenesis and the rhizobial infection. MicroRNAs (miRNAs) act as post-transcriptional regulators in the development of new organ or in response to environmental stimuli. Previosuly, we have described that the miR390 dramatically decreased (80%) in roots of the model legume Medicago truncatula at early stages of its interaction with Sinorhizobium meliloti. miR390 targets the non-coding RNA TAS3 and triggers the production of trans-acting small interference RNAs (tasiRNAs). TAS3-derived tasiRNAs control the stability of transcripts encoding the Auxin Response Factors ARF2, 3 and 4. Expression analysis in different organs indicated that this pathway is very active in stem and young nodules. Overexpression of a precursor of miR390 resulted in a reduction in the number and size of nodules, as well as in the number of infection events. On the other hand, expression of a mimicry, which sequestrates miR390 blocking its action on TAS3 transcript, increased the number of nodules; but negatively affected nodule develpment and infection. These results suggest that the miR390 and tasiRNAs pathway fine-tune regulates nodule development and rhizobial infection in M. truncatula.