Identification of differentially expressed genes of Haloxylon ammodendron in response to salinity stress

Haloxylon ammodendron (C.A. Mey.), an endangered desert tree with excellent drought and salinity tolerance, provides a unique genotype to characterize and understand the tolerance mechanisms. In this study, four RNA-Seq libraries were constructed and sequenced from H. ammodendron under salinity stress. Total 12 027 differentially expressed genes (DEGs) were identified, in which 4 023, 3 517, 4 487 genes were differentially expressed under light salinity stress (200 mM NaCl), moderate salinity stress (400 mM NaCl), and severe salinity stress (800 mM NaCl), respectively. The up-regulated DEGs included several transcription factors (e.g., MYB and bHLH), hormone-related genes (e.g., cytochrome P450), protein kinases (e.g., Atpk2-Atpk19 like), and genes involved in carbon metabolism (e.g., UDP glycosyltransferase), osmotic regulation (e.g., proline transporter), and ubiquitin proteasome system (e.g., ubiquitin-conjugating enzymes). Heat shock proteins were identified as positive regulators of salinity tolerance in H. ammodendron. The expression patterns of 13 DEGs verified by real-time quantitative PCR were identically consistent with the variations in transcript abundance identified by RNA-Seq. Our results provide new insights into molecular mechanism of H. ammodendron in response to salinity stress.