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Root-hair endophyte stacking in finger millet creates a physicochemical barrier to trap the fungal pathogen Fusarium graminearum

2016; Nature Portfolio; Volume: 1; Issue: 12 Linguagem: Inglês

10.1038/nmicrobiol.2016.167

2058-5276

Walaa K. Mousa, Charles Shearer, Victor Limay‐Rios, Cassandra L. Ettinger, Jonathan A. Eisen, Manish N. Raizada,

Nematode management and characterization studies

The ancient African crop, finger millet, has broad resistance to pathogens including the toxigenic fungus Fusarium graminearum. Here, we report the discovery of a novel plant defence mechanism resulting from an unusual symbiosis between finger millet and a root-inhabiting bacterial endophyte, M6 (Enterobacter sp.). Seed-coated M6 swarms towards root-invading Fusarium and is associated with the growth of root hairs, which then bend parallel to the root axis, subsequently forming biofilm-mediated microcolonies, resulting in a remarkable, multilayer root-hair endophyte stack (RHESt). The RHESt results in a physical barrier that prevents entry and/or traps F. graminearum, which is then killed. M6 thus creates its own specialized killing microhabitat. Tn5-mutagenesis shows that M6 killing requires c-di-GMP-dependent signalling, diverse fungicides and resistance to a Fusarium-derived antibiotic. Further molecular evidence suggests long-term host–endophyte–pathogen co-evolution. The end result of this remarkable symbiosis is reduced deoxynivalenol mycotoxin, potentially benefiting millions of subsistence farmers and livestock. Further results suggest that the anti-Fusarium activity of M6 may be transferable to maize and wheat. RHESt demonstrates the value of exploring ancient, orphan crop microbiomes. A symbiosis between the root-inhabiting Enterobacter sp. M6 and the finger millet creates a physical barrier around the roots, trapping and killing the fungus Fusarium graminearum via M6-derived release of fungicides into the barrier matrix.