Streptomyces-Induced 6-Nitrocoumarin Coordinates Rhizosphere Microbiome Recruitment for Pepper Blight Suppression

Phytophthora capsici causes devastating losses in global pepper production. This study deciphers a sophisticated plant-microbe-metabolite collaboration initiated by rhizosphere-colonizing Streptomyces. We demonstrate that Streptomyces specifically primes pepper root biosynthesis of 6-nitrocoumarin, a nitrated coumarin derivative exhibiting potent broad-spectrum antioomycete activity (EC₅₀: P. capsici 44.39 mg/L, Phytophthora palmivora 47.06 mg/L, Peronophythora litchii 34.92 mg/L). Crucially, this Streptomyces-recruited metabolite functions as a keystone rhizosphere signal, selectively enriching beneficial bacterial consortia while directly disrupting the ABC transporters of pathogens. The restructured microbiome synergistically amplifies plant systemic resistance through upregulating defense genes and enhancing root immunity. Our work establishes 6-nitrocoumarin as a dual-functional inoculant, a direct actinomycete compound and microbiome modulator, revealing a novel plant-microbe codefense paradigm driven by Streptomyces-induced metabolic rewiring for sustainable crop protection.