Regulatory small RNAs involved in the symbiosis between Phaseolus vulgaris and Rhizobium etli

MÉLISSE CASTAINGTS, CAROLINA RÍPODAS, O. MARIO AGUILAR, FLAVIO BLANCO AND MARÍA EUGENIA ZANETTI

Chascomús

Congreso; XV Jornadas Anuales de la Sociedad Argentina de Biología; 2013

Sociedad Argentina de Biología

Common bean (Phaseolus vulgaris) establishes a symbiotic interaction with Rhizobium etli, resulting in the formation of root nitrogen-fixing nodules. Interestingly, beans from the Mesoamerican center of genetic diversification are more efficiently and preferentially nodulated by strains that are predominant in the same geographical region. Our group has identified several transcription factors that are determinant for this preferential interaction. One of them encodes an A subunit of the heterotrimeric transcription factor NF-Y named PvNF-YA1. PvNF-YA1 is strongly expressed at early stages of the interaction with the highly efficient strain of R. etli, but not with the less efficient one, suggesting a special function in strain specificity. In silico analysis revealed that PvNF-YA1 could be regulated by two microRNAs (miR169b and miR169d) through their putative target sites, which are present in the 3?UTR of the PvNF-YA1 transcript. Overexpression of a miR169 resistant version of PvNF-YA1 resulted in an increase in the number of nodules formed by the less efficient strain. RT-PCR analysis revealed that miR169d precursor is specifically and highly expressed in young nodules formed by the highly efficient strain, where two different spliced variant where identified. Simultaneously, in order to get access to global changes in small RNAs (sRNAs) abundance during this symbiotic interaction, we have constructed sRNAs libraries of roots inoculated with the more or the less efficient strain that will be subjected to Illumina sequencing. This approach will allow us to identify new sRNAs involved in the preferentially association.