miR390 and 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; ZANETTI, MARÍA EUGENIA

Mar del Plata

Congreso; XV Congreso Latinoamericano XXX Reunión Argentina de Fisiología Vegetal; 2014

The development of nitrogen fixing nodules depends on the activation of two highly coordinated genetic programs present in leguminous plants: the root hair infection and the nodule organogenesis. MicroRNAs (miRNAs) act as post-transcriptional regulators during organ development or in response to environmental stimuli. Previously, we have described that levels of miR390 dramatically decreased (80%) in roots of the model legume Medicago truncatula at early stages of the interaction with Sinorhizobium meliloti. miR390 targets the non-coding RNA TAS3, triggering 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 indicated that this pathway is very active in stem and young nodules. Overexpression of the precursor of miR390 resulted in a reduction in the number and size of nodules, as well as the number of infection events. On the other hand, expression of a mimicry construct, which blocks tasiRNA production by sequestering miR390, increased the number of nodules, but negatively affected nodule development and infection. These results suggest that miR390 and the tasiRNAs pathway participate in the fine-tune regulation of nodule development and rhizobial infection in M. truncatula.