iTRAQ-based proteomic technique provides insights into salt stress responsive proteins in Apocyni Veneti Folium (Apocynum venetum L.)

Abstract Soil salinity is a major abiotic stress that limits plant growth and productivity. Understanding the mechanisms of plant salinity tolerance can facilitate engineering for quality improvement. Apocynum venetum L. exhibits tolerance to salinity. Due to the lack of a genomic database, RNA-seq based transcriptomics and isobaric tag for relative and absolute quantitation (iTRAQ) based proteomic profiles of Apocyni Veneti Folium (leaves of Apocynum venetum L.) exposure to four levels of salt treatments (0, 100, 200 and 300 mM NaCl, respectively) were performed. A total of 143, 162 and 167 differentially expressed proteins (DEPs) were found between salt-treated Apocyni Veneti Folium compared with control, respectively. They were mainly involved in carbohydrate and energy metabolism, biosynthesis of metabolites and signal transduction. Furthermore, results showed that carbon and nitrogen metabolisms were altered under salt stress; low and moderate levels of salt stress enhanced photosynthetic functions and ramped up carbohydrate metabolism. However, severe salt stress depressed biosynthesis of secondary metabolites, consistent with the metabolomics results. It is worth emphasizing that some key salt-responsive proteins, such as dehydrin 1, annexin, pathogenesis-related protein, prolyl oligopeptidase, peroxidase, cinnamyl alcohol dehydrogenase, 4-hydroxycinnamoyl-CoA ligase 3, cytochrome P450 CYP73A120, were screened. These novel proteins provide a good starting point for further research into their functions using genetic or other approaches. In addition, a weak correlation between the abundance of DEPs and the corresponding differentially expressed genes highlighted the effect of post-transcriptional modifications and the importance of employing proteomics and transcriptomics to analyze global protein level changes. In conclusion, the protein profiles indicate that halophyte uses a multipronged approach to overcome salt stress, and provides some novel information on revealing the mechanisms of adaption and quality formation.