microRNA miR171h modulates arbuscular mycorrhizal colonization of Medicago truncatula by targeting NSP2

• Published in: The Plant journal : for cell and molecular biology 2012-11, Vol.72 (3), p.512-522
• Main Authors: Lauressergues, Dominique, Delaux, Pierre‐Marc, Formey, Damien, Lelandais‐Brière, Christine, Fort, Sébastien, Cottaz, Sylvain, Bécard, Guillaume, Niebel, Andreas, Roux, Christophe, Combier, Jean‐Philippe
• Format: Article
• Language: English
• Subjects: arbuscular mycorrhizal symbiosis; arbuscular mycorrhizas; Binding Sites; Biological and medical sciences; Colonization; Elongation; embryophytes; Exudates; Fundamental and applied biological sciences. Psychology; Fungi; Gene Expression; Gene Expression Regulation, Plant; Glomeromycota - cytology; Glomeromycota - genetics; Glomeromycota - growth & development; Glomeromycota - physiology; Glomus intraradices; Lactones - metabolism; Lipopolysaccharides - metabolism; Medicago truncatula; Medicago truncatula - cytology; Medicago truncatula - genetics; Medicago truncatula - microbiology; Medicago truncatula - physiology; messenger RNA; microRNA; MicroRNAs - genetics; MicroRNAs - metabolism; Mimicry; miR171; miRNA; mRNA; mutants; Mycorrhizae - cytology; Mycorrhizae - genetics; Mycorrhizae - growth & development; Mycorrhizae - physiology; mycorrhizal fungi; NSP2; Parasitism and symbiosis; Phenotype; Phylogeny; Plant ecology; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Roots - genetics; Plant Roots - metabolism; Plant Roots - microbiology; Rhizophagus; rhizosphere; RNA, Plant - genetics; RNA, Plant - metabolism; root exudates; Roots; Signal Transduction; Symbiosis; Transcription Factors - genetics; Transcription Factors - metabolism; Up-Regulation; vesicular arbuscular mycorrhizae
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2012.05099.x

Most land plants live symbiotically with arbuscular mycorrhizal fungi. Establishment of this symbiosis requires signals produced by both partners: strigolactones in root exudates stimulate pre‐symbiotic growth of the fungus, which releases lipochito‐oligosaccharides (Myc‐LCOs) that prepare the plant for symbiosis. Here, we have investigated the events downstream of this early signaling in the roots. We report that expression of miR171h, a microRNA that targets NSP2, is up‐regulated in the elongation zone of the root during colonization by Rhizophagus irregularis (formerly Glomus intraradices) and in response to Myc‐LCOs. Fungal colonization was much reduced by over‐expressing miR171h in roots, mimicking the phenotype of nsp2 mutants. Conversely, in plants expressing an NSP2 mRNA resistant to miR171h cleavage, fungal colonization was much increased and extended into the elongation zone of the roots. Finally, phylogenetic analyses revealed that miR171h regulation of NSP2 is probably conserved among mycotrophic plants. Our findings suggest a regulatory mechanism, triggered by Myc‐LCOs, that prevents over‐colonization of roots by arbuscular mycorrhizal fungi by a mechanism involving miRNA‐mediated negative regulation of NSP2.