Linking the miR390/TAS3 and the Nod signaling pathways during the nitrogen-fixing symbiosis

HOBECKER, KAREN; BOHNER, SANTIAGO; REYNOSO, MAURICIO; BUESTOS, PILAR; CRESPI, MARTÍN; BLANCO, FLAVIO; ZANETTI, MARÍA EUGENIA

Buenos Aires

Congreso; XVIII Jornadas Anuales Interdisciplinarias Sociedad Argentina de Biología; 2016

LINKING THE miR390/TAS3 AND THE NOD SIGNALING PATHWAYS DURING THE NITROGEN-FIXING SYMBIOSIS Hobecker K.V.1, Bohner S1, Reynoso M1, Bustos P2, Crespi M2, Blanco F1, Zanetti M.E1. 1IBBM, FCE-UNLP CCT-CONICET. 2IPS, University of Paris Saclay, France.MicroRNAs (miRNAs) act as post-transcriptional regulators of gene expression during development or in response to environmental stimuli. Under low nitrogen conditions, legume roots establish symbiotic associations with soil bacteria known as rhizobium that results in the development of a new organ, the nodule, within which rhizobia fix the atmospheric nitrogen into reduced forms that are readily assimilated by the plant. Previous analysis in M. truncatula revealed that levels of miR390 are reduced at early stages of the symbiotic interaction. miR390 targets the non-coding transcript TAS3 and triggers the production of the trans-acting small interference RNAs (tasiRNAs). In turn, these tasiRNAs control the stability of transcripts encoding the Auxin Response Factors 2, 3 and 4 (ARF2/3 /4). Overexpression of miR390 (OX390) negatively affected nodule organogenesis and rhizobial infection. On the other hand, expression of a target mimicry of the miR390 (MIM390), which significantly reduced tasiARFs production, enhanced nodulation and altered the morphology and distribution of nodules. Activation of the miR390/TAS3 pathway prevented the induction of the Nodulation Signaling Pathway 1(NSP1) and NSP2 genes in response to rhizobial infection, whereas inactivation of this pathway results in increased levels of NSP1/2, NIN and ERN1, even in the absence of rhizobia. These results suggest that the miR390/TAS3 pathway regulates, either directly or indirectly, the expression of symbiotic genes that are essential for nodulation. Ongoing RNA-seq and ChIP-seq analysis will allow us to identify the putative direct targets of this pathway under symbiotic conditions.