Dicranopteris dichotoma rhizosphere-derived Bacillus sp. MQB12 acts as an enhancer of plant growth via increasing phosphorus utilization, hormone synthesis, and rhizosphere microbial abundance

In recent years, microbial inoculants have showed a great potential to replace chemical fertilizers as a new generation of soil amendment agents, however, the understanding of their effects on nutrient cycling within plants and rhizosphere microbial diversity are still limited. In this study, the rhizosphere growth-promoting bacteria MQB12 was used to inoculate Vigna radiata to evaluate the effects of external inoculants on plant transcriptomics and rhizosphere soil microbial diversity. Enrichment analysis using GO and KEGG revealed significant enrichment in DNA-binding transcription factor activity, transcriptional regulatory factor activity, and phenylpropanoid biosynthesis among the differentially expressed genes. MQB12 inoculation positively responded to phosphorus starvation response, increased the expression of phosphorus starvation response genes (PHT/PAP), enhanced the synthesis of ethylene and salicylic acid to cope with external stress, and improved the expression of plant disease resistance genes to strengthen the disease resistance of plants to pathogens. At the same time, microbial diversity analysis further revealed the positive effect of MQB12 inoculum. MQB12 inoculum enriched beneficial flora, improved flora abundance, changed the structure and diversity of V. radiata rhizosphere microbial community, enhanced the interconnections between the flora, and positively promoted growth. MQB12 was found to adjust the microflora of the rhizosphere, which subsequently changed the environment for plant colonization. This change led to the enrichment of beneficial bacteria and removal of pathogenic bacteria, which positively affected the internal pathways of plants. Additionally, changes in gene expression levels of plants resulted in the formation of different phenotypes and various metabolites, further influencing the formation of rhizosphere microbial communities through close contact between roots and soil. This study provides new insights into the effects of microbial agents on plant growth and root environment construction and is conducive to the further development and application of microbial agents.