Physiological response and transcriptome analysis of Hordeum brevisubulatum under mixed salt and alkaline stress

In order to study the physiological response and salt tolerance genes of wild barley (Hordeum brevisubulatum) under saline alkali stress, 45-day-old seedlings were treated with different concentrations of NaCl and NaHCO₃. The critical value of saline alkali stress was determined by physicochemical analysis. The gene expression was analysed by RNA-Seq. The soluble protein content and superoxide dismutase (SOD) activity of wild barley leaves increased first and then decreased after treatment with different concentrations of NaCl and NaHCO₃ (100, 200, 300, 400, 500 mmol·L^–1) for 2 days. The maximum value was reached at 300 mmol·L^–1, and the content of proline and soluble sugar showed a continuous upward trend. The wild barley leaves in the 300 mmol·L^–1 treatment group were sequenced and analysed. Compared with the control group (treatment of salt and alkali free), 4 163 genes were up-regulated and 1 936 genes were down-regulated. The Gene Ontology (GO) function classification of the differentially expressed genes could be divided into 52 subclasses of three main categories: biological process, cell component, and molecular function. A total of 4 405 differential genes were annotated into 132 pathways, mainly involved in sucrose synthesis, proline synthesis, peroxisome metabolic pathways. The genes encoding sucrose synthase (SuS), ornithine aminotransferase (OAT), glutamate kinase (proB), glutamate-5-semialdehyde dehydrogenase (proA), superoxide dismutase (SOD) were up-regulated. Wild barley can adapt to saline alkali stress by increasing the content of some osmotic regulators, this metabolic process regulates the physiological mechanism of regulating the expression of related genes.