An attapulgite--Bacillus amyloliquefaciens biocontrol agent increases growth and medicinal metabolite content in Angelica sinensis by modulating hormonal and phenylpropanoid pathways

Beneficial interactions between host plants and rhizosphere microbes can increase plant growth, suppress plant disease, and promote sustainable production. In previous work, we demonstrated that a novel biocontrol agent consisting of attapulgite-coated Bacillus amyloliquefaciens FZB42 (APBA) effectively controlled Fusarium root rot in the well-known medicinal herb Angelica sinensis . Here, we sought to examine how APBA would affect the growth and medicinal metabolite content of A. sinensis under chemical and organic fertilizer regimes. Inoculation with B. amyloliquefaciens FZB42 in the greenhouse or application of APBA in the field significantly enhanced growth and yield of A. sinensis , regardless of whether it was applied with chemical or organic fertilizer. Levels of secondary metabolites such as shikimate and isoferulic acid were higher in APBA-treated plants, particularly when APBA was applied together with organic fertilizer. Transcriptome analysis revealed that APBA treatment altered the expression of genes encoding pathogenesis-related proteins, heat shock proteins, antioxidant enzymes, and various transcription factors, as well as genes associated with hormone signaling and primary and secondary metabolism. Some responses to APBA differed depending on the fertilizer regime: APBA had a greater effect on phenylpropanoid metabolite levels and upregulated expression of more hormone-related genes when applied with organic fertilizer. This study provides insights into the molecular responses of A. sinensis to a bacterial biocontrol agent, providing a foundation for further research and practical applications of B. amyloliquefaciens FZB42 in sustainable agriculture.