RNA-Seq De Novo Assembly of Red Pitaya (Hylocereus polyrhizus) Roots and Differential Transcriptome Analysis in Response to Salt Stress

Pitaya (Hylocereus polyrhizus) is a highly valued functional food that is widely planted in Southeast Asia. However, with increased soil salinization in cultivation areas, a better understanding of the molecular mechanisms associated with salt stress responses in red pitaya is necessary. Herein, RNA-Seq was used to de novo assemble and characterize the transcriptomic profiles of red pitaya roots in response to salt stress. A total of 73,589 transcripts were obtained and the average sequence length was 1308 bp. From these transcripts, 26,878 unique transcripts were successfully matched to 13,519 Swiss-prot proteins. Gene ontology (GO) annotations showed that within the categories of molecular function, biological function, and cell component, catalytic activity (GO:0003824), metabolic process (GO:0008152), and cell part (GO:0044464) were the most enriched, respectively. 2624 transcripts were significantly differentially expressed among three time points (3 h, 7 h, and 30 h) following exposure to 450 mM NaCl. Furthermore, 261 genes were up-regulated and 61 down-regulated in all three of the time points. Glycolysis/gluconeogenesis was one of the most significantly modulated pathways. The findings presented herein provide further insight into salt stress responses in pitaya and will provide a valuable resource for future functional studies examining salt adaptations.