De novo transcriptome analysis of Fraxinus velutina Torr in response to NaCl stress

This study aimed to further clarify the mechanisms of salt-alkali tolerance in Fraxinus velutina Torr. Shoots obtained from Fraxinus velutina Torr (also known as velvet ash or Arizona ash) and of Fraxinus chinensis Roxb (controls) were planted in a greenhouse with hydroponics and 1-year-old seedlings were irrigated with 40 mM NaCl, followed by 80 mM NaCl; young leaves were then harvested and sequenced from total RNA. Differential expression gene analyses of Fraxinus velutina Torr as well as that of Fraxinus chinensis Roxb before and after treatment were conducted. The Gene Ontology biological process (GO-BP) terms and pathways enriched by overlapping genes were analyzed, and the co-expression network of them was built. A total of 454 overlapping upregulated and 278 overlapping downregulated genes were found in the two comparisons. Upregulated genes were mainly enriched in GO-BP terms of alkaloid biosynthetic process, and the pathways such as Ras signaling pathway, while downregulated genes were primarily enriched in photosynthesis and phenylpropanoid biosynthesis. The processes of phenylpropanoid biosynthesis and photosynthesis, as well as metallothionein-like protein and photosystem I P700–related proteins, appear to be involved in salt stress tolerance in Fraxinus velutina Torr.