Transcriptome sequencing and functional analysis of Sedum lineare Thunb. upon salt stress

Soil salinization is one major constraint to plant geographical distribution, yield, and quality, and as an ideal plant for the "greening" of flat-roofed buildings, Sedum lineare Thunb. has strong tolerance against a variety of environmental adversities including salinity with the underlying mechanism still remaining unknown. In this study, we performed de novo transcriptome sequencing on leaf and root samples of NaCl-treated S. lineare Thunb. and identified 584 differentially expressed genes (DEGs), which were further annotated by gene function classification and pathway assignments using the public data repositories. In addition to the increased gene expression level verified by qRT-PCR, the elevated activities of the corresponding enzymes were also demonstrated for peroxidase (POD), glutathione peroxidases (GPX), and cysteine synthase (CSase) in the NaCl-treated roots. Furthermore, two highly inducible genes without known functions related to salt tolerance were selected to be overexpressed and tested for their effects on salt tolerance in the model plant, Arabidopsis thaliana. Upon 150 mM NaCl treatment, 35S:SlCXE but not 35S:SlCYP72A transgenic Arabidopsis seedlings exhibited improved salt resistance as shown by the increased seed germination rates and longer primary roots of transgenic seedlings when compared to wild-type plants. Taken together, this work laid a foundation for a better understanding of the salt adaptation mechanism of S. lineare Thunb. and genes identified could serve as useful resources for the development of more salt-tolerant varieties of other species through genetic engineering.