Integrated Physiological and Omics Analyses Reveal Endophytic Streptomyces Regulates N and P Uptake, Utilization, and...

The inherent deficiency of available nitrogen (N) and phosphorus (P) in acidic soils severely limits productivity in agriculture and forestry. While plant-beneficial microorganisms offer a sustainable solution, the mechanisms by which endophytic actinobacteria regulate N and P absorption and utilization remain largely unexplored. In this study, we characterize Streptomyces sp. CoH27, an endophyte isolated from Camellia oleifera, which exhibits pronounced abilities in N fixation and insoluble P solubilization. Inoculation with CoH27 significantly promoted the growth of C. oleifera across different ages and propagation types, as evidenced by enhanced root architecture, improved photosynthetic parameters, and increased N and P absorption and utilization efficiencies. Physiological analyses revealed that CoH27 colonization upregulated the activity of key enzymes involved in organic acid synthesis and N assimilation in roots, thereby enhancing rhizosphere P mobilization and plant N utilization. Furthermore, CoH27 reshaped the rhizosphere microbiome, increasing bacterial diversity and the abundance of beneficial taxa, while reinforcing microbial networks. The driving effect of nutrient cycling was evidenced with enriched abundance of microbial genes involved in P solubilization (phnA, ppa) and N metabolism (nasA, narB, amoA, nxrA). Concurrently, transcriptomics identified the upregulation of critical transporter genes (CoPHT1;4, CoNRT2.5) and transcription factors in CoH27-inoculated roots, orchestrating improved N and P uptake and assimilation. The efficacy of CoH27 was further validated in Brassica napus L. and Capsicum annuum L., underscoring its potential as a versatile microbial inoculant to enhance sustainable crop production in acidic soils.