Comparative Transcriptome Analysis of Leaves of Sour Jujube Seedlings under Salt Stress

Sour jujube is a tree species native to China, which has often been used as the rootstock for the propagation of other cultivars of jujube. In addition, its fruit can be used in the practice of traditional Chinese medicine. Thus, sour jujube has been regarded as a highly valuable plant scientifically and ecologically. Sour jujube is mostly planted in Northwest China and has extremely high salt tolerance. However, the molecular mechanism of its salt tolerance is yet to be fully understood. This study was carried out in the Laboratory of Agricultural College of Dalian Nationalities University. Two treatments were performed on the leaves of sour jujube seedlings with the experimental group (H3) being treated by 300 mM NaCl for 3 h, and the control group (CK) by sterile water for 3 h. A total of 47.02 GB of valid data and 32,730 annotated genes were obtained. Based on the gene expression in the comparison group, 2295 significantly differentially expressed genes (DEGs) were obtained, of which 807 and 1488 were upregulated and downregulated, respectively. According to gene function annotation and enrichment analysis, 148 genes were obtained, which are mainly involved in signal transduction of plant hormones (38), homeostasis of cell walls (27), secondary metabolism of organic matter (32), and redox reactions (20) in the leaves of sour jujube seedlings under salt stress. Among these DEGs, some stress-related transcription factors (31) were also identified. In addition, under salt stress, raffinose family oligosaccharide (RFO) metabolism in sour jujube seedlings was found to be greatly accelerated. By investigating the molecular responses of jujube seedlings under salt stress, our study provides a scientific basis for jujube cultivation in saline-alkali land, which is beneficial to further improvement of the salt tolerance of grafted jujube trees.