Abstract Soil salinization and alkalinization threaten plant growth worldwide. In response, plants deploy various physiological and molecular defense mechanisms. Nanobiotechnology offers a potential strategy to enhance crop stress tolerance. Here, we found that nano-Fe₃O₄ increased salt-alkali tolerance in melon seedlings by suppressing the expression of the transcription factor CmBHLH93. Transcriptomic analysis revealed strong downregulation of CmBHLH93 upon nano-Fe₃O₄ application under salt-alkali stress. Functional assays showed that CmBHLH93 acted as a negative regulator of salt tolerance. It directly bound the promoters of key defense-related genes involved in ABA synthesis (CmNCED3), JA synthesis (CmAOS), antioxidant activity (CmPOD-1), and Na+ transport (CmSOS1), thereby repressing their transcription. Taken together, nano-Fe₃O₄ enhanced melon salt tolerance by downregulating CmBHLH93 transcription and activating downstream responses associated with ABA/JA signaling, antioxidant capacity, and Na+/K+ homeostasis. These results define a regulatory mechanism through which nanomaterials modulate plant tolerance to salt-alkali stress and provide a conceptual basis for improving crop stress tolerance using nanotechnology.
Tan et al. (2026) studied this question.