| Summary: | While bHLH transcription factors have been linked to the regulation of various abiotic stressors, research on drought-related bHLH proteins and their molecular processes in <i>Agropyron mongolicum</i> has remained limited. In this study, a bHLH gene from <i>A. mongolicum</i>, designated as <i>AmbHLH148</i>, was successfully cloned and isolated. <i>AmbHLH148</i> was exclusively localized within the nucleus. Additionally, qRT-PCR analysis demonstrated a significant upregulation of <i>AmbHLH148</i> in response to drought stress. When transferred into tobacco (<i>Nicotiana benthamiana</i>), the heterologous expression of <i>AmbHLH148</i> led to enhanced drought tolerance. Under drought stress conditions, <i>AmbHLH148</i>-OE transgenic tobacco plants exhibited increased activities of antioxidant defense enzymes, such as SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase). These enzymes efficiently mitigated the accumulation of reactive oxygen species (ROS) compared to wild-type plants. Furthermore, <i>AmbHLH148</i>-OE transgenic tobacco showed elevated levels of PRO (proline) and reduced MDA (malondialdehyde) content, contributing to enhanced stability in the plant’s cell membrane system during drought stress. In summary, this study underscores that the overexpression of <i>AmbHLH148</i> in transgenic tobacco acts as a positive regulator under drought stress by enhancing the plant’s antioxidant capacity. These findings shed light on the molecular mechanisms involved in bHLH transcription factors’ role in drought resistance, contributing to the discovery and utilization of drought-resistant genes in <i>A. mongolicum</i> for enhancing crop drought resistance.
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