Caffeic acid product from the highly copper-tolerant plant Elsholtzia splendens post-phytoremediation:its extraction,purification,and identification

In the current study,caffeic acid was an important metabolite in the highly copper-tolerant plant Elsholtzia splendens.Preparation and purification of caffeic acid were performed on the dried biomass of the plants by means of sonication/ethanol extraction,followed by purification using a macroporous resin (D101 type) column and silica gel chromatography.The faint-yellow caffeic acid product was yielded with a purity of 98.46%,and it was chemically identified from spectra of Fourier transform infrared spectroscopy (FTIR),proton nuclear magnetic resonance (1 H NMR)/carbon nuclear magnetic resonance (13 C NMR),and electrospray ionization mass spectrometry (ESI-MS).Caffeic acid is a possible product from the post-harvest processing of Elsholtzia splendens biomass.

OTS_1-dependent deSUMOylation increases tolerance to high copper levels in Arabidopsis

The conjugation of SUMO （small ubiquitin-like modifier） to protein substrates is a reversible process （SUMOylation/deSUMOylation） that regulates plant devel- opment and stress responses. The essential metal copper （Cu） is required for normal plant growth, but excess amounts are toxic. The SUMO E3 ligase, SIZI, and SIZ1- mediated SUMOylation function in plant tolerance to excess Cu. It is unknown whether deSUMOylation also contributes to Cu tolerance in plants. Here, we report that OTSI, a protease that cleaves SUMO from its substrate proteins, participates in Cu tolerance in Arabidopsis thaliana （Arabi- dopsis）. OTS1 loss-of-function mutants （otsl-2 and otsl-3） displayed increased sensitivity to excess Cu. Redox homeostasis and the balance between SUMOylation and deSUMOylation were disrupted in the otsl-3 mutant under excess Cu conditions, The otsl-3 mutant accumulated higher levels of Cu in both shoots and roots compared to wild type. Specific Cu-related metal transporter genes were upregu- lated due to the loss-of-function of OTS% which might explain the high Cu levels in otsl-3. These results suggest that the SUMOylation/deSUMOylation machinery is acti- vated in response to excess Cu, and modulates Cu homeostasis and tolerance by regulating both Cu uptake and detoxification. Together, our findings provide insight into the biological function and regulatory role of SUMOylation/deSUMOylation in plant tolerance to Cu.