Physiological and transcriptomic profiles of tobacco seedling leaves in response to high chloride accumulation

Tobacco is a special commercial crop that prefers potassium but not chlorine, and excessive chloride (Cl^–) accumulation can cause toxicity. Here, we revealed that the structural characteristics of chloroplasts in tobacco leaves were significantly destroyed under high Cl^– salinity, but not mitochondria. Large differences in leaf structure, MDA content, and antioxidant enzyme activities were observed for the treatment with highest chloride accumulation at the 14th day. Moreover, RNA-seq analysis of tobacco leaves exposed to high Cl^– salinity revealed global changes in gene transcription levels. A total of 1360 DEGs involved in cell wall, lipid, starch, and secondary metabolism processes were unevenly distributed on chromosomes, and were mainly enriched for starch and sucrose metabolism, phenylpropanoid biosynthesis, ribosome and ribosome biogenesis, protein processing in the endoplasmic reticulum, and plant hormone signal transduction pathways. Overall, our study provides valuable insights for further research on the mechanism underlying Cl^– salinity and salt-tolerant tobacco development.

烟草是一类喜钾忌氯的特色经济作物，过量氯离子（Cl⁻）积累会引发毒害效应。本研究发现，高氯盐胁迫下烟草叶片叶绿体的结构特征会发生显著破坏，而线粒体结构未受明显影响。在处理第14天时，高氯离子积累组的叶片结构、丙二醛（Malondialdehyde，MDA）含量以及抗氧化酶活性均出现显著差异。此外，对高氯盐胁迫下的烟草叶片进行RNA测序（RNA-seq）分析，结果显示其基因转录水平发生了全局性变化。共计1360个差异表达基因（Differentially Expressed Genes，DEGs）参与细胞壁、脂质、淀粉及次生代谢过程，在染色体上呈非均匀分布，且主要富集于淀粉与蔗糖代谢、苯丙烷生物合成、核糖体及核糖体发生、内质网蛋白质加工以及植物激素信号转导通路。综上，本研究为深入解析氯盐胁迫的分子机制以及耐盐烟草品种培育提供了重要参考依据。