Green fluorescent carbon dots remodel soil microbial communities and regulate gene expression to enhance the salt stress adaptability of wheat

The escalating soil salt stress poses a severe threat to food security, while existing mitigation strategies suffer from multiple limitations. As a low-toxicity nanomaterial, carbon dots (CDs) exhibit significant potential in enhancing plant stress resistance. This study focuses on the mechanism by which CDs alleviate salt stress in wheat through regulating wheat genes and soil microorganisms. Wheat plants grown in soil were subjected to salt stress and CDs treatment. Subsequently, plant samples, rhizosphere soil samples, and bulk soil samples were collected. The activities of plant antioxidant enzymes, malondialdehyde (MDA) content, and ion contents were determined. Additionally, transcriptome analysis and soil microbial community analysis were conducted. Under 150 mM NaCl stress, the application of CDs at a concentration of 15 mg/L significantly enhanced the growth performance and physiological stress tolerance of wheat. This enhancement was manifested by an increase in plant height (11.3%) and biomass (47.7%), as well as a substantial elevation in the activities of key antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Meanwhile, CDs remarkably inhibited the accumulation of malondialdehyde (MDA) and effectively maintained Na⁺/K⁺ homeostasis. At the molecular level, transcriptome analysis revealed that CDs triggered extensive gene reprogramming, with 374 and 872 differentially expressed genes (DEGs) identified in the shoots and roots, respectively. These DEGs were mainly enriched in pathways such as plant hormone signal transduction, glutathione metabolism, and metal ion binding. Furthermore, the application of CDs reshaped the structure of the soil microbial community, indicating that CDs enhance plant adaptability to salt stress through a multi-faceted mechanism. Carbon dots effectively maintain Na⁺/K⁺ homeostasis and thereby alleviate salt stress in wheat by synergistically activating the plant's antioxidant defense/growth regulation system and reshaping the rhizosphere microbiome.