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

María Reyero-Saavedra,Marc Libault,Alejandra Covarrubias,María Sánchez-Correa,Jose Reyes,M Díaz-Pineda,Oswaldo Valdés-López,Zhenzhen Qiao

doi:10.3390/genes8120352

María Reyero-Saavedra, Marc Libault + Show 6 more

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https://doi.org/10.3390/genes8120352

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Abstract

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 (Glycine max) seeds. Here, we show that AGO5 is also playing a central role in legume nodulation based on its preferential expression in common bean (Phaseolus vulgaris) 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 AGO5 gene in P. vulgaris and G. max causes diminished root hair curling, reduces nodule formation and interferes with the induction of three critical symbiotic genes: Nuclear Factor Y-B (NF-YB), Nodule Inception (NIN) and Flotillin2 (FLOT2). Our findings provide evidence that the common bean and soybean AGO5 genes play an essential role in the establishment of the symbiosis with rhizobia.

Highlights

Legumes can establish symbiosis with nitrogen-fixing bacteria
In order to identify new regulators of the symbiosis between legumes and nitrogen-fixing rhizobia, we conducted a data-mining analysis on transcriptional data from P. vulgaris interacting with rhizobia
P. vulgaris AGO5 (PvAGO5), we evaluated the expression of the molecular role played by PvAGO5, we evaluated the expression of the symbiosis-related genes: symbiosis-related genes: Nodulation-signalling pathway2 (PvNSP2), Nodule inception protein

Summary

Introduction

Legumes can establish symbiosis with nitrogen-fixing bacteria (rhizobia). It has been estimated that the legume-rhizobia symbiosis fixes 60 million metric tons of nitrogen worldwide, and reduces the use of synthetic fertilizers [2]. To establish this symbiosis, a molecular dialog between rhizobia and legume partners is required [3,4]. The rhizobia synthesize and exude lipo-chitooligosaccharides (LCOs), known as Nod Factors (NFs). The legume-host perceives NFs via LysM-domain receptor kinases Nod Factor Receptor and 5 (NFR1 and NFR5), both located at the legume root hair plasma membrane.

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