Functional Interaction of ROS and Nitric Oxide during Induction of Heat Resistance of Wheat Seedlings by Hydrogen Sulfide Donor

Abstract

The participation of reactive oxygen species (ROS) and nitric oxide (NO), and also enzymatic systems generating them, in the development of heat resistance of wheat (Triticumaestivum L.) seedlings, induced by the hydrogen sulfide (H2S) donor sodium hydrosulfide (NaHS), has been studied. It was found that 24-h pretreatment of seedlings with 0.1–1 mM NaHS increased their survival after the subsequent 10-min damaging heating at 45°C. The content of hydrogen peroxide and nitric oxide increased together with the nitrate reductase (NR) activity in the seedling roots within the first 4 h of their treatment with the H2S donor. The rise in the NO level significantly suppressed by the inhibitor of NR sodium tungstate but not the inhibitor of NO synthase (NG-nitro-L-arginine methyl ester, L-NAME). The hydrogen peroxide scavenger dimethylthiourea (DMTU) and the NADPH oxidase inhibitor imidazole abolished the increase in NR activity and NO content in the roots. However, the nitric oxide scavenger (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, PTIO) and the inhibitors of the NO-producing enzymes only weakly influenced the increase in H2O2 content caused by the root treatment with sodium hydrosulfide. The NaHS-induced rise in the seedling heat resistance was eliminated by both ROS antagonists (DMTU and imidazole) and NO antagonists (PTIO and tungstate). It is concluded that the boost in the wheat seedling heat resistance, which is caused by exogenous hydrogen sulfide, is mediated by the increased ROS generation, followed by NR activation, and resultant rise in the level of nitric oxide produced by this enzyme.