Physiological and transcriptomic analyses revealed the alleviating effects of exogenous Ca and NO compound treatment on high salt stress in Reaumuria soongorica.

Background: Soil salinization represents the most prevalent abiotic stress, severely impacting a severe impact on plant growth and crop yield. Consequently, delving into the mechanism through which exogenous substances enhance plant salt tolerance holds significant importance for the stabilization and augmentation of crop yield.

Result: In this study, within the context of salt stress, the seedlings of R. soongorica were subjected to exogenous Ca and NO treatments. The aim was to comprehensively explore the alleviation effects of exogenous Ca and NO on the high salt stress endured by R. soongorica from the perspectives of physiology and transcriptomics. The experimental results demonstrated that the combined treatment of exogenous Ca and NO increased the relative water content and free water content of R. soongorica seedlings during salt stress conditions. Simultaneously, it induced a reduction in the leaf sap concentration, leaf water potential, water saturation deficit, and the ratio of bound water to free water. These modifications effectively regulated water metabolism and mitigated physiological drought induced by salt stress. In addition, the concurrent treatment of exogenous Ca and NO could diminish Na and Cl levels in R. soongorica seedlings under salt stress. At the same time, it was effective in elevating the contents of K and Ca, thereby facilitating the adjustment of the ion equilibrium. As a result, this treatment served to relieve the ion toxicity precipitated by salt stress, which is crucial for maintaining the physiological homeostasis and viability of the seedlings. Transcriptional analysis revealed that 65 differentially expressed genes (DEGs) were observable at three distinct stress time points in the context of high salt stress. Additionally, 154 DEGs were detected at three stress time points during the combined treatment. KEGG enrichment analysis revealed that phenylpropanoids biosynthesis, plant hormone signal transduction, MAPK signalling pathway, brassinosteroid biosynthesis and zeatin biosynthesis were significantly enriched under high salt stress and exogenous Ca and NO compound treatment. Furthermore, WGCNA uncovered that multiple genes, including ADK, SBT, F-box protein, MYB, ZIP, PAL, METTL, and LRR, were implicated in the adaptive and mitigating mechanisms associated with the combined treatment of exogenous Ca and NO in modulating high salt stress within R. soongorica seedlings.

Conclusion: The outcomes of this study are highly conducive to disclosing the mechanism through which the combined treatment of exogenous Ca and NO ameliorates the salt tolerance of R. soongorica from both physiological and transcriptional aspects. It also paves a solid theoretical groundwork for the employment of biotechnology in the breeding of R. soongorica, thereby offering valuable insights and a scientific basis for further research and practical applications in enhancing the plant's ability to withstand salt stress and for the development of more salt-tolerant varieties of R. soongorica.