Insight into the mechanisms of Cd(II) on significantly enhancing rhizobacterial ACC deaminase activity in Cd-tolerant Ensifer morelensis A23T

Cadmium (Cd)-tolerant plant growth-promoting rhizobacteria have garnered significant attention in Cd 2+ remediation owing to their dual capabilities of mitigating heavy metal stress and enhancing plant growth. A rhizobacterial strain exhibiting elevated 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production was isolated from Cd-contaminated soil and genotypically characterized as Ensifer morelensis A23T. This work establishes the first documented evidence of significantly enhanced ACC deaminase activity in Ensifer morelensis under 50 mg L −1 Cd 2+ exposure. Genomic analysis identified multiple functional genes implicated in Cd 2+ tolerance and plant growth promotion. Transcriptome profiling revealed that Cd 2+ stress significantly induced the expression of ACC deaminase-associated genes while concurrently downregulating cell cycle-related genes, suggesting a potential adaptive response to Cd-induced cytotoxicity. Furthermore, inoculation with strain A23T significantly enhanced rapeseed germination and seedling growth under Cd 2+ stress. These findings underscore the potential utilization of strain A23T as a sustainable biological agent to support plant growth in cadmium-affected soils and provide novel insights into its molecular adaptation strategies to heavy metal stress.