A halotolerant strain of Bacillus cereus effectively regulates salt stress-responsive genes in Zea mays L. seedlings under stress condition.

Abstract

Soil salinity severely constrains agricultural productivity worldwide, particularly affecting salt-sensitive crops such as maize (Zea mays L.) at early developmental stages. Plant growth-promoting rhizobacteria (PGPR) have emerged as a promising strategy to mitigate salinity stress; however, the underlying molecular mechanisms remain incompletely understood. In this study, we identified a salinity stress tolerance-promoting (SSTP) strain, Bacillus cereus isolate 74 (originally isolated from a salt-marshland environment), and investigated its role in enhancing salt tolerance in maize through integrated physiological and transcriptomic analyses. Phenotypic screening revealed that SSTP inoculation significantly improved plant growth parameters, chlorophyll content, and ionic balance under salinity stress. To elucidate the molecular basis of this response, RNA sequencing of maize roots was performed, identifying 307 high-confidence differentially expressed genes (DEGs). Functional enrichment analysis demonstrated that SSTP inoculation predominantly modulated pathways associated with oxidative stress mitigation, metabolic and catabolic processes, and cellular responses to chemical stimuli. Notably, genes involved in hydrogen peroxide detoxification, transport activity, and stress-responsive transcriptional regulation were significantly upregulated. These findings indicate that B. cereus isolate 74 enhances maize salt tolerance through coordinated regulation of antioxidant defense systems and metabolic reprogramming. This study provides novel insights into PGPR-mediated stress adaptation and highlights the potential application of SSTP strains in sustainable agriculture under saline conditions.