Bacillus amyloliquefaciens ART9 modulates the growth of Radix serratulae Chinensis through rhizosphere microbiome reprogramming and root transcriptomic regulation
Objective Continuous cropping obstacles and heavy chemical fertilizer use constrain Radix serratulae chinensis cultivation. This study evaluates the optimal concentration of plant growth-promoting rhizobacterium Bacillus amyloliquefaciens ART9 and investigates its underlying mechanisms via rhizosphere microbiome and host transcriptome analyses. Methods Seedlings were treated with ART9 suspensions at OD600 of 0.4, 0.6, and 1.0. Growth parameters, soil nutrient contents, rhizosphere bacterial communities, and root transcriptomic profiles were assessed to compare treatment effects. Results The OD600 0.6 treatment yielded the best performance, increasing plant height, stem diameter, and SPAD value by 48.56%, 14.09%, and 12.42%, respectively, over the control, and raising soil available nitrogen, phosphorus, and potassium by 177%, 179%, and 168%. Rhizosphere microbiota were significantly enriched with beneficial genera, notably Bacillus, Pseudomonas, and Sphingomonas. Transcriptomics revealed prominent enrichment in phenylpropanoid biosynthesis (map00940), plant hormone signal transduction (map04075), and circadian rhythm–plant (map04712) pathways. Upregulated genes included JAZ, ABF, PYL, PP2C, SPA1_2, and HY5, indicating coordinated regulation of hormone and light signaling. Conclusion ART9 systematically promotes growth of Radix serratulae chinensis by reshaping the rhizosphere microbiome and modulating hormone/light signaling pathways, supporting its development as a sustainable biofertilizer for medicinal plant production.