MICRORNA390 REGULATES LATERAL ROOT

REYNOSO MA , HOBECKER K , BUSTOS P , BLANCO F , CRESPI M , ZANETTI ME

Mendoza

Congreso; Reunión Anual de la SAIB (Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular); 2012

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular

1IBBM, FCE-UNLP CCT-CONICET.  2ISV, CNRS, Gif sur Yvette, France. MicroRNAs have emerged as major regulators of gene expression during development or in response to environmental stimuli. Plant roots adapt to the local environment to maximize water and nutrient acquisition by adjusting their developmental programs. Under low nitrogen availability, roots of legumes establish a symbiotic association with soil bacteria called rhizobia, which results in the formation of a new root organ specialized in nitrogen fixation, the nodule. We have identified several microRNAs that change their abundance in roots of the model legume Medicago truncatula at early stagesof its interaction with Sinorhizobium meliloti. One of these miRNAs, miR390, dramatically decreased (~80%) in response to S. meliloti. miR390 targets the non-coding RNA TAS3 and triggers the production of tasiARFs. In turn, tasiARFs control the stability or translatability of ARF2, 3 and 4 transcripts. Consistent with the decrease on miR390 abundance, inoculation with S. meliloti led to an increase on the abundance of TAS3 precursor, a decrease in tasiARFs production and higher accumulation of ARF transcripts. Overexpression of the miR390 resulted in an increase of lateral root length, and a reduction in the number of symbiotic nodules. These results suggest that miR390 might be part of a pathway that negatively controls nodule organogenesis, but promotes lateral root growth in M. truncatula.