Dipartimento Agricoltura, Ambiente e Alimenti, Università degli Studi del Molise, Campobasso, Italy.
Departamento de Genetica, Campus de Excelencia Internacional Agroalimentario ceiA3, Universidad de Córdoba, Córdoba, Spain.
Nat Commun. 2020 Oct 16;11(1):5264. doi: 10.1038/s41467-020-18994-5.
Soil-inhabiting fungal pathogens use chemical signals released by roots to direct hyphal growth towards the host plant. Whether other soil microorganisms exploit this capacity for their own benefit is currently unknown. Here we show that the endophytic rhizobacterium Rahnella aquatilis locates hyphae of the root-infecting fungal pathogen Fusarium oxysporum through pH-mediated chemotaxis and uses them as highways to efficiently access and colonize plant roots. Secretion of gluconic acid (GlcA) by R. aquatilis in the rhizosphere leads to acidification and counteracts F. oxysporum-induced alkalinisation, a known virulence mechanism, thereby preventing fungal infection. Genetic abrogation or biochemical inhibition of GlcA-mediated acidification abolished biocontrol activity of R. aquatilis and restored fungal infection. These findings reveal a new way by which bacterial endophytes hijack hyphae of a fungal pathogen in the soil to gain preferential access to plant roots, thereby protecting the host from infection.
土壤定殖真菌病原体利用根系释放的化学信号来引导菌丝向宿主植物生长。目前尚不清楚其他土壤微生物是否利用这种能力来谋取自身利益。在这里，我们表明，根内细菌 Rahnella aquatilis 通过 pH 介导的趋化性定位到根侵染真菌病原体 Fusarium oxysporum 的菌丝，并利用它们作为高效进入和定植植物根系的高速公路。R. aquatilis 在根际分泌葡萄糖酸（GlcA）会导致酸化，并抵消 F. oxysporum 诱导的碱化，这是一种已知的毒力机制，从而防止真菌感染。GlcA 介导的酸化的遗传缺失或生化抑制消除了 R. aquatilis 的生物防治活性，并恢复了真菌感染。这些发现揭示了一种新的方式，即细菌内生菌在土壤中劫持真菌病原体的菌丝，以优先进入植物根系，从而保护宿主免受感染。
