Dynamics of cytoplasmic mRNAs at early stages of the nitrogen fixing symbiosis between the model legume Medicago truncatula and Sinorhizobium meliloti

LANCIA, MARCOS; REYNOSO, MAURICIO; BLANCO, FLAVIO; ZANETTI, MARÍA EUGENIA

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

Eukaryotic mRNAs associate to RNA-binding proteins that influence their stability, transport, cellular localization and translatability. In the cytoplasm, mRNAs can be translated into polysomes, targeted for degradation into P-bodies or stored in cytoplasmic granules. We have genome-wide characterized changes in the association of mRNAs to polysomes in roots of the model legume Medicago truncatula at early stages of the symbiotic interaction with Sinorhizobium meliloti using Translating Ribosomes Affinity Purification (TRAP) combined with RNA -Seq technology. This analysis identified a number of mRNAs that do not change in total abundance, but are significantly up- or down-regulated at the level of association with polysomes.  The first category includes genes that have shown to play essential roles in nodulation, such as those encoding a pectate lyase and a SINA family member. The second category contains mRNAs that dissociate from polysomes upon rhizobial infection and is represented by NCR secreted peptides, receptor-like kinases and SAUR-auxin responsive proteins. Differential recruitment of these mRNAs to polysomes is being validated by RT-qPCR in the whole root and in specific tissue types.  The dynamic partitioning of mRNAs between polysomes, P-bodies  and cytoplasmic granules  is currently being evaluated by affinity purification of these RNA-protein complexes.