This work aims at studying the molecular mechanisms underlying the response of Reaumuria soongorica to salt stress. We used RNA sequencing (RNA-Seq) and Tandem Mass Tag (TMT) techniques to identify differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) in R. soongorica leaves treated with 0, 200, and 500 mM NaCl for 72 h. The results indicated that compared with the 0 mM NaCl treatment group, 2391 and 6400 DEGs were identified in the 200 and 500 mM NaCl treatment groups, respectively, while 47 and 177 DEPs were also identified. Transcriptome and proteome association analysis was further performed on R. soongorica leaves in the 0/500 mM NaCl treatment group, and 32 genes with consistent mRNA and protein expression trends were identified. SYP71, CS, PCC13-62, PASN, ZIFL1, CHS2, and other differential genes are involved in photosynthesis, vesicle transport, auxin transport, and other functions of plants, and might play a key role in the salt tolerance of R. soongorica. In this study, transcriptome and proteome association techniques were used to screen candidate genes associated with salt tolerance in R. soongorica, which provides an important theoretical basis for understanding the molecular mechanism of salt tolerance in R. soongorica and breeding high-quality germplasm resources.

Soil salinization is a common abiotic stress that severely limits the growth of Reaumuria soongarica and reduces its application value. To better understand the response of R. soongarica to salt stress and the physiological mechanisms of exogenous Ca²⁺ and NO compound treatment in alleviating salt stress, the growth parameters, antioxidant system, carbohydrate metabolism and nitrogen compound metabolism were compared on Days 0, 1, 3, 6, 9, 15 and 30. The results showed that salt stress could significantly reduce the plant height, root length, fresh and dry weights of aboveground and underground parts, as well as the relative water content, severely inhibiting the growth of R. soongarica seedlings. After Ca²⁺ and NO compound treatment, these growth parameters were significantly improved, and the harm caused by stress in R. soongarica was alleviated. Regarding the antioxidant system, the Ca²⁺ and NO compound treatment could significantly increase the activities of SOD, CAT, APX and GR, as well as the contents of ASA and GSH, which indicated that exogenous Ca²⁺ and NO could eliminate the accumulated active oxygen by increasing the activities of oxidoreductases and the content of nonenzymatic antioxidant substances, thereby improving the salt tolerance of R. soongarica. Regarding carbon metabolism, after Ca²⁺ and NO compound treatment, the soluble sugar and sucrose contents, as well as the activities of sucrose phosphate synthase and sucrose synthase, were significantly increased, which indicated that Ca²⁺ and NO compound treatment could maintain higher soluble sugar and sucrose contents in R. soongarica and reduce osmotic stress caused by salt treatment. Regarding nitrogen metabolism, the Ca²⁺ and NO compound treatment reduced the harm of salt stress by regulating the nitrogen compound contents and nitrogen compound-related enzyme activities, including increases in the NO₃⁻ content and NR, NiR, GS, GOGAT and GDH activities and a reduction in the NO₂⁻ content. The results of this study indicate that the inhibition of the growth and development of R. soongarica by salt stress can be alleviated by regulating the antioxidant system, carbohydrate metabolism and nitrogen compound metabolism, which provides a theoretical basis for Ca²⁺ and NO compound treatment to improve plant salt tolerance.