Bacillus velezensis D103 enhances maize drought tolerance via ROS-scavenging and phenylpropanoid pathway activation

Bacillus velezensis D103 improves drought tolerance through enhanced antioxidant activity and lignin deposition, with VIGS analysis indicating roles for ZmAPX3, ZmAOX1B, ZmPER72, and ZmPRX74. Drought stress is a major abiotic constrain on global crop productivity. The application of plant growth-promoting rhizobacteria (PGPR) offers a promising strategy to enhance plant drought tolerance, yet the associated molecular mechanisms remain incompletely characterized. In this study, we examined the role of Bacillus velezensis D103 in maize drought responses by assessing physiological and transcriptomic changes. Under drought stress, D103 inoculation supported plant growth and increased leaf relative water content (RWC), reducing the RWC deficit from 12.4% to 5.1%. This response was accompanied by greater lignin deposition (28.5%) and higher antioxidant enzyme activities. Transcriptome data showed that D103 treatment activated key drought-associated pathways, including glutathione metabolism and phenylpropanoid biosynthesis. VIGS assays suggested that ZmAPX3 (glutathione metabolism), ZmAOX1B (ROS-scavenging), and ZmPER72 and ZmPRX74 (phenylpropanoid metabolism) contribute to the drought tolerance observed in D103-treated plants. Overall, the findings suggest that B. velezensis D103 supports maize drought tolerance by regulating lignin biosynthesis and ROS-related processes. This study provides insights into PGPR-mediated stress resistance responses and highlights strain D103 as a candidate microbial inoculant for improving crop performance under water-limited conditions.