Effects of plant growth regulators on antibiotic resistance genes transfer through conjugation and transformation

Antibiotic resistance genes (ARGs) are exacerbated by horizontal gene transfer. Plant growth regulators (PGRs), extensively applied in agriculture, may further accelerate the environmental dissemination of ARGs. However, research on PGR influence on environmental ARG spread remains limited. This study elucidates the impact of three PGRs-indole-3-acetic acid (IAA), ethephon (ETH), and gibberellic acid (GA₃)-on ARG transfer via conjugation and transformation pathways. Key results demonstrate that IAA (800 mg/L) significantly increased conjugation frequency despite reducing recipient survival by 99%. This effect correlated with IAA-induced increases in cell membrane permeability and reactive oxygen species (ROS) accumulation. Conversely, ETH and GA₃ exhibited no significant impact on conjugation. In transformation assays, IAA failed to enhance transformation efficiency due to ROS-induced cellular toxicity. In contrast, ETH (200 mg/L) and GA₃ (800 mg/L) enhanced transformation efficiency via moderate ROS-induced activation of competence genes. Collectively, PGR effects are concentration-dependent and pathway-specific. IAA primarily drives conjugative transfer through enhanced membrane permeability and ROS generation while ETH and GA₃ selectively boost transformation efficiency. These findings identify PGRs as potential drivers of environmental AMR dissemination, thus informing strategies for mitigating resistance spread within agricultural ecosystems.

The online version contains supplementary material available at 10.1007/s12298-026-01730-6.