Conserved and novel miRNAs influence strain preference in the Phaseolus vulgaris-Rhizobium etli nitrogen fixing symbiosis

MARIA EUGENIA ZANETTI

Córdoba

Congreso; Reunion Argentina De Fisiología Vegetal; 2018

Sociedad Argentina de Fisiología Vegetal

Phaseolus vulgaris (common bean) establishes a nitrogenfixing symbiosis with its partner Rhizobium etli.Beans from the Mesoamerican center of genetic diversificationexhibited a preference for highly efficient andcompetitive strains, which is governed by an exchangeof signals and the reprogramming of gene expressionin both symbionts. MicroRNAs (miRNAs) are endogenoussmall RNAs that participate in the control of geneexpression in eukaryotes, mainly at post-transcriptionallevel. Here, we used a small RNA-seq approach to identifyconserved and novel miRNAs that differentially accumulatein root cells at early stages of a high efficientsymbiotic interaction. Conserved miRNAs includedmiR167a, mi171a and miR390b. Functional analysisof miR390b demonstrated that this miRNA acts as anegative regulator of nitrogen fixing symbiosis in commonbean. The analysis of a novel miRNA -designatedmiR5924- revealed that the mature miR5924 is processedfrom a stem-loop precursor located in the 5´UTRof a type III RNAse transcript and has a receptor involvedin plant defense as the putative target. Overexpressionof miR5924 altered strain preference and decreasedthe outcome of the symbiotic interaction. The roleof this miRNAs in the suppression of defense responsesrequired for the successful establishment of thesymbiotic interaction will be discussed.