Hydrogen sulfide - cysteine cycle plays a positive role in Arabidopsis responses to Copper Oxide nanoparticles stress

Copper Oxide (II) nanoparticles (CuO NPs) are the most important nanomaterials, which also have a strong toxicity for plants. Hydrogen sulfide (H2S) is a newly appreciated gasotransmitter participant in plant stress physiology. Here, we investigated the role of H2S-cysteine (Cys) cycle in plant responses to CuO NPs stress. H2S and Cys synthetic regulating related genes l-Cysteine desulfhydrase (LCD), l-Cysteine Desulfhydrase 1 (DES1) and O-acetylserine(thiol)lyase isoform A1 (OASA1) levels were successively induced by CuO NPs, and endogenous H2S and Cys contents increased, suggesting that H2S-Cys cycle responses to CuO NPs stress. The tolerance of CuO NPs weakened in lcd, des1, lcddes1 or oasa1 mutants. Subcellular distribution of Cu was disturbed, and organelle's Cu concentration increased in mutants. Chemical forms of Cu changed when H2S-Cys cycle was blocked. Heavy metal chelator proteins were up-regulated under CuO NPs stress in Col-0, but the levels were weakened in mutants. H2S-Cys cycle also regulated antioxidase activity and maintained ROS homeostasis in CuO NPs stress. The black particles appeared in root tip after CuO NPs treatment, which formed by CuO NPs. By contrast Col-0, the black particles significantly accumulated in mutants, suggesting that H2S signal affects CuO NPs uptake and intracellular transport. Conclusion, H2S-Cys cycle plays a positive role in plant responses to CuO NPs stress.