Integrated plant physiology, transcriptomics, and metabolomics reveal tobacco root growth and nicotine synthesis responses in tobacco exposure to different nitrogen forms

Tobacco (Nicotiana tabacum L.) is one of the world’s most economically important crops, with nicotine content being a crucial factor in determining its quality and economic value. By integrating plant physiology with transcriptomics and metabolomics analyses, we gained insight into the regulation of nicotine synthesis and metabolism in tobacco seedlings under different forms of nitrogen supply. Our findings revealed that ammonium nitrogen promotes nitrogen transformation in the root system of tobacco seedlings but inhibits root growth, whereas nitrate nitrogen inhibits biochemical processes but enhances root growth. Additionally, we observed that nitrate nitrogen facilitates the NAD + pathway in nicotine biosynthesis but inhibits the polyamine pathway, whereas ammonium nitrogen has the opposite effect. Overall, our comprehensive analysis indicates that the co-application of ammonium nitrate is conducive to nicotine synthesis. These results not only contribute to identifying key genes and metabolites involved in nicotine synthesis, but also provide a theoretical basis for establishing efficient regulation theories and pathways for tobacco's nitrogen utilization. Furthermore, they offer scientific support for future efforts aimed at regulating tobacco nicotine synthesis.

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