Gene Silencing of Argonaute5 Negatively Affects the Establishment of the Legume-Rhizobia Symbiosis

The establishment of the symbiosis between legumes and nitrogen-fixing rhizobia is finely regulated at the transcriptional, posttranscriptional and posttranslational levels. Argonaute5 (AGO5), a protein involved in RNA silencing, can bind both viral RNAs and microRNAs to control plant-microbe interactions and plant physiology. For instance, AGO5 regulates the systemic resistance of Arabidopsis against Potato Virus X as well as the pigmentation of soybean ( ) seeds. Here, we show that AGO5 is also playing a central role in legume nodulation based on its preferential expression in common bean ( ) and soybean roots and nodules. We also report that the expression of AGO5 is induced after 1 h of inoculation with rhizobia. Down-regulation of gene in and causes diminished root hair curling, reduces nodule formation and interferes with the induction of three critical symbiotic genes: Nuclear Factor Y-B ( ), Nodule Inception ( ) and Flotillin2 ( ). Our findings provide evidence that the common bean and soybean genes play an essential role in the establishment of the symbiosis with rhizobia.