Beta vulgaris L. is one of the main sugar-producing crop species and is highly adaptable to saline soil. This study explored the alterations to the carbon and nitrogen metabolism mechanisms enabling the roots of sugar beet seedlings to adapt to salinity. The ionome, metabolome, and transcriptome of the roots of sugar beet seedlings were evaluated after 1 day (short term) and 7 days (long term) of 300 mM Na+ treatment. Salt stress caused reactive oxygen species (ROS) damage and ion toxicity in the roots. Interestingly, under salt stress, the increase in the Na+/K+ ratio compared to the control ratio on day 7 was lower than that on day 1 in the roots. The transcriptomic results showed that a large number of differentially expressed genes (DEGs) were enriched in various metabolic pathways. A total of 1279 and 903 DEGs were identified on days 1 and 7, respectively, and were mapped mainly to 10 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Most of the genes were involved in carbon metabolism and amino acid (AA) biosynthesis. Furthermore, metabolomic analysis revealed that sucrose metabolism and the activity of the tricarboxylic acid (TCA) cycle increased in response to salt stress. After 1 day of stress, the content of sucrose decreased, whereas the content of organic acids (OAs) such as L-malic acid and 2-oxoglutaric acid increased. After 7 days of salt stress, nitrogen-containing metabolites such as AAs, betaine, melatonin, and (S)-2-aminobutyric acid increased significantly. In addition, multiomic analysis revealed that the expression of the gene encoding xanthine dehydrogenase (XDH) was upregulated and that the expression of the gene encoding allantoinase (ALN) was significantly downregulated, resulting in a large accumulation of allantoin. Correlation analysis revealed that most genes were significantly related to only allantoin and xanthosine. Our study demonstrated that carbon and nitrogen metabolism was altered in the roots of sugar beet plants under salt stress. Nitrogen metabolism plays a major role in the late stages of salt stress. Allantoin, which is involved in the purine metabolic pathway, may be a key regulator of sugar beet salt tolerance.

中文翻译：

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转录组学和代谢组学分析揭示了甜菜根中碳和氮代谢发生改变的盐度适应机制

甜菜（Beta vulgaris L.）是主要的产糖作物品种之一，对盐渍土的适应性很强。本研究探讨了碳和氮代谢机制的改变，使甜菜幼苗的根部能够适应盐度。经过 1 天（短期）和 7 天（长期）300 mM Na+ 处理后，对甜菜幼苗根部的离子组、代谢组和转录组进行了评估。盐胁迫导致根部活性氧（ROS）损伤和离子毒性。有趣的是，在盐胁迫下，第 7 天根部 Na+/K+ 比率与对照比率相比的增加低于第 1 天。转录组结果显示，各种代谢途径中富集了大量差异表达基因（DEG）。第 1 天和第 7 天分别鉴定出 1279 个和 903 个 DEG，主要映射到 10 个京都基因和基因组百科全书 (KEGG) 通路。大多数基因参与碳代谢和氨基酸（AA）生物合成。此外，代谢组学分析表明，蔗糖代谢和三羧酸（TCA）循环的活性随着盐胁迫而增加。胁迫1天后，蔗糖含量下降，而L-苹果酸、2-酮戊二酸等有机酸(OA)含量增加。盐胁迫7天后，AA、甜菜碱、褪黑素、(S)-2-氨基丁酸等含氮代谢物显着增加。此外，多组学分析显示，编码黄嘌呤脱氢酶（XDH）的基因表达上调，编码尿囊素酶（ALN）的基因表达显着下调，导致尿囊素大量积累。相关分析显示，大多数基因仅与尿囊素和黄苷显着相关。我们的研究表明，在盐胁迫下，甜菜植物根部的碳和氮代谢发生了变化。氮代谢在盐胁迫后期发挥着重要作用。尿囊素参与嘌呤代谢途径，可能是甜菜耐盐性的关键调节剂。