Combined Transcriptional and Metabolic Analysis of the Differences in Salt Tolerance Responses of Tillers in Different Rice Varieties

<title>Abstract</title> Background Soil salinization is a significant factor contributing to the reduction of arable land. To enhance rice productivity in saline-alkali soils, understanding the salt tolerance mechanisms of rice varieties is essential. This study focused on investigating the salt tolerance mechanisms in the tillers of two rice varieties: the salt-tolerant CMG and the salt-sensitive 9311, using morphophysiological, transcriptomic, and metabolomic methods. Results The activities of antioxidant enzymes SOD, POD, and APX in the tiller nodes of CMG were significantly higher than those in 9311. In contrast, the levels of MDA (malondialdehyde) and hydrogen peroxide in CMG tiller nodes were relatively lower, suggesting a more effective response to salt stress. Both varieties responded to saline-alkali stress through similar metabolic pathways, including amino acid metabolism (such as alanine, aspartic acid, glutamic acid metabolism, and arginine biosynthesis), amino acid acyl-tRNA biosynthesis, oxidative phosphorylation, and phenylpropanoid biosynthesis. However, CMG exhibited unique metabolic pathways such as glycerophospholipid metabolism, which is associated with membrane lipid remodeling, and the biosynthesis of the stratum corneum, suppositories, and waxes, which play a key role in reducing water loss and preventing sodium ion entry. Additionally, CMG showed a greater ability to regulate plant hormone signaling pathways, particularly those involving abscisic acid (ABA) and jasmonic acid (JA), to coordinate the expression and metabolic activities of defense genes. Conclusion The tiller nodes of CMG primarily focus on strengthening their own defenses against stress and reducing Na + toxicity after salt stress. In contrast, the tiller nodes of 9311 enhance photosynthetic efficiency by transferring stress responses to the leaves. This study provides valuable insights into the molecular mechanisms and metabolic pathway dynamics of salt tolerance in rice, offering a new perspective for further research on the salt tolerance mechanisms of rice under saline-alkali stress.