De Novo Transcriptome Characterization, Gene Expression Profiling and Ionic Responses of Nitraria sibirica Pall. under Salt Stress

Nitraria sibirica Pall., a typical halophyte of great ecological value, is widely distributed in desert, saline, and coastal saline-alkali environments. Consequently, researching the salt tolerance mechanism of N. sibirica Pall. has great significance to the cultivation and utilization of salt-tolerant plants. In this research, RNA-seq, digital gene expression (DGE), and high flux element analysis technologies were used to investigate the molecular and physiological mechanisms related to salt tolerance of N. sibirica Pall. Integrative analysis and de novo transcriptome assembly generated 137,421 unigenes. In total, 58,340 and 34,033 unigenes were annotated with gene ontology (GO) terms and mapped in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, respectively. Three differentially expressed genes (DEGs) libraries were subsequently constructed from the leaves of N. sibirica Pall. seedlings under different treatments: control (CK), light short-term salt stress (CL2), and heavy long-term salt stress (CL6). Eight hundred and twenty-six, and 224 differentially expressed genes were identified in CL2 and CL6 compared to CK, respectively. Finally, ionomic analysis of N. sibirica Pall. seedlings treated with 0, 100, 200 or 300 mM concentrations of NaCl for one day showed that the uptake and distribution of Ca, Cu, Fe, Mg and K in different organs of N. sibirica Pall. were significantly affected by salt stress. Our findings have identified potential genes involved in salt tolerance and in the reference transcriptome and have revealed the salt tolerance mechanism in N. sibirica Pall. These findings will provide further insight into the molecular and physiological mechanisms related to salt stress in N. sibirica Pall. and in other halophytes.