Transcriptome analyses revealed molecular responses of Cynanchum auriculatum leaves to saline stress.

Cynanchum auriculatum is a traditional herbal medicine in China and can grow in saline soils. However, little is known in relation to the underlying molecular mechanisms. In the present study, C. auriculatum seedlings were exposed to 3.75‰ and 7.5‰ salinity. Next, transcriptome profiles of leaves were compared. Transcriptome sequencing showed 35,593 and 58,046 differentially expressed genes (DEGs) in treatments with 3.75‰ and 7.5‰, compared with the control, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of these DEGs enriched various defense-related biological pathways, including ROS scavenging, ion transportation, lipid metabolism and plant hormone signaling. Further analyses suggested that C. auriculatum up-regulated Na+/H+ exchanger and V-type proton ATPase to avoid accumulation of Na+. The flavonoid and phenylpropanoids biosynthesis pathways were activated, which might increase antioxidant capacity in response to saline stress. The auxin and ethylene signaling pathways were upregulated in response to saline treatments, both of which are important plant hormones. Overall, these results raised new insights to further investigate molecular mechanisms underlying resistance of C. auriculatum to saline stress.

Selection of solvent for extraction of antioxidant components from Cynanchum auriculatum, Cynanchum bungei, and Cynanchum wilfordii roots.

In east Asia, "Baishouwu" has been used as an herbal drug and functional dietary supplement for hundreds of years. Actually, "Baishouwu" is the common name of the roots of Cynanchum auriculatum, Cynanchum bungei, and Cynanchum wilfordii. In the present study, roots of these three specie were extracted and then fractionated using petroleum ether (PE), dichloromethane (DCM), ethyl acetate (EA), and water. DPPH scavenging experiments revealed high antioxidant activity of DCM and EA fractions of C. bungei and the EA fraction of C. wilfordii. Treatments with these three fractions significantly reduced malondialdehyde content in heat-stressed Daphnia magna, validating in vivo antioxidant activity. Gas chromatography-mass spectrometer (GC-MS) analyses demonstrated that the chemical components of fractions extracted from C. bungei, C. bungei, and C. wilfordii were different. Further determination of total phenol and total flavonoids contents showed that DCM and EA fractions of C. bungei and EA fraction of C. wilfordii had much higher contents of total phenol and total flavonoids, which might be the reason to explain their strong antioxidant activity. Overall, the present study suggested that these three plants have different chemical components and biological activities. They could not be used as the same drug.