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

Soil salinization stands out as a major factor contributing to the shrinkage of arable land. This study explored the salt tolerance mechanism of tillers in CMG and 9311 by evaluating morphophysiological, transcriptomic, and metabolomic characteristics under 0.3% NaCl stress. The activities of SOD, POD, and APX in the tiller nodes of the salt-tolerant variety CMG were higher than those of 9311, while the levels of MDA and hydrogen peroxide in the tiller nodes of CMG were relatively low. Both varieties responded to salt stress mainly by activating pathways such as amino acid metabolism (alanine, aspartic acid, glutamic acid metabolism, and arginine biosynthesis), amino acid acyl-trNA biosynthesis, oxidative phosphorylation, and phenylpropanin biosynthesis. The varieties differed in that CMG tillering nodes also have unique pathways of “glycerophospholipid metabolism” (related to membrane lipid remodeling) and “biosynthesis of the cuticle, suppositories and waxes”, which can effectively reduce water loss and prevent sodium ions from entering. In addition, CMG can regulate more plant hormone signaling pathways to coordinate the expression and metabolic activities of downstream defense genes, such as abscisic acid (ABA) and jasmonic acid (JA), and other hormone signals. After salt stress, the CMG tiller nodes tend to strengthen themselves, enabling them to resist stress and reduce Na+ toxicity, while the 9311 tiller nodes, under the condition of activating basal metabolism, transfer to the leaves to enhance photosynthetic efficiency and resist stress. Through comprehensive screening and analysis of the genes and metabolites of CMG and 9311 tillers under salt stress, the molecular mechanisms and metabolic pathway dynamics involved in their salt stress response were identified, thus providing a new perspective for in-depth research on rice salt tolerance mechanisms.