Department of Biology, Faculty of Science, University of Tabuk, Tabuk 71491, P.O. Box 741, Saudi Arabia.
Department of Biology, Faculty of Science, University of Tabuk, Tabuk 71491, P.O. Box 741, Saudi Arabia.
Nitric Oxide. 2017 Aug 1;68:91-102. doi: 10.1016/j.niox.2017.01.001. Epub 2017 Jan 3.
Nitric oxide (NO) and hydrogen sulfide (HS) have been shown to act as signaling molecules in various physiological processes, play significant roles in plant cellular processes, and also mediate responses to both biotic and abiotic stresses in plants. The present investigation was carried out to test the effect of exogenous NO on endogenous synthesis of HS in osmotic-stressed wheat (Triticum aestivum L.) seedlings. The results show that application of NO to wheat seedlings, suffered from PEG8000-induced osmotic stress, considerably enhanced the activities of HS-synthesizing enzymes l-cysteine desulfhydrase (LCD) and d-cysteine desulfhydrase (DCD) leading to enhanced level of endogenous HS content. At the same time exogenous NO also enhanced the activity of cysteine (Cys)-synthesizing enzyme O-acetylserine(thiol)lyase (OAS-TL) and maintained Cys homeostasis under osmotic stress. NO and HS together markedly improved the activities of antioxidant enzymes viz. ascorbate peroxidase (APX), glutathione reductase (GR), peroxidase (POX), superoxide dismutase (SOD) and catalase (CAT). Furthermore, NO and HS caused additional accumulation of osmolytes proline (Pro) and glycine betaine (GB), all these collectively resulted in the protection of plants against osmotic stress-induced oxidative stress. On the other hand, NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] and HS scavenger HT (hypotaurine) invalidated the effect of NO on endogenous HS levels and Cys homeostasis which resulted in weak protection against osmotic stress. Application of N-ethylmaleimide (NEM) suppressed GR activity and caused an increase in oxidative stress. We concluded that NO in association with endogenous HS activates the defense system to the level required to counter osmotic stress and maintains normal functioning of cellular machinery.
一氧化氮 (NO) 和硫化氢 (HS) 已被证明在各种生理过程中作为信号分子发挥作用，在植物细胞过程中发挥重要作用，并且介导植物对生物和非生物胁迫的反应。本研究旨在测试外源 NO 对渗透胁迫小麦 (Triticum aestivum L.) 幼苗内源 HS 合成的影响。结果表明，NO 处理PEG8000 诱导渗透胁迫的小麦幼苗，可显著增强 HS 合成酶 l-半胱氨酸脱硫酶 (LCD) 和 d-半胱氨酸脱硫酶 (DCD) 的活性，导致内源 HS 含量增加。同时，外源 NO 还增强了半胱氨酸 (Cys) 合成酶 O-乙酰丝氨酸(巯基)裂解酶 (OAS-TL) 的活性，并在渗透胁迫下维持 Cys 平衡。NO 和 HS 共同显著提高了抗氧化酶活性，如抗坏血酸过氧化物酶 (APX)、谷胱甘肽还原酶 (GR)、过氧化物酶 (POX)、超氧化物歧化酶 (SOD) 和过氧化氢酶 (CAT)。此外，NO 和 HS 导致渗透胁迫诱导的氧化应激中渗透物质脯氨酸 (Pro) 和甘氨酸甜菜碱 (GB) 的额外积累，所有这些共同导致植物对渗透胁迫的保护。另一方面，NO 清除剂 cPTIO [2-(4-羧基苯基)-4,4,5,5-四甲基咪唑啉-1-氧-3-氧化物] 和 HS 清除剂 HT (次牛磺酸) 使 NO 对内源 HS 水平和 Cys 平衡的影响无效，导致对渗透胁迫的保护作用减弱。N-乙基马来酰亚胺 (NEM) 的应用抑制了 GR 活性并导致氧化应激增加。我们得出结论，NO 与内源性 HS 一起激活防御系统，使其达到对抗渗透胁迫的要求水平，并维持细胞机制的正常功能。
