Department of Botany and Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia.
Department of Botany and Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia.
Nitric Oxide. 2020 Jan 1;94:95-107. doi: 10.1016/j.niox.2019.11.002. Epub 2019 Nov 7.
Despite numerous reports on the role of nitric oxide (NO) in regulating plants growth and mitigating different environmental stresses, its participation in sulfur (S) -metabolism remains largely unknown. Therefore, we studied the role of NO in S acquisition and S-assimilation in tomato seedlings under low S-stress conditions by supplying NO to the leaves of S-sufficient and S-deficient seedlings. S-starved plants exhibited a substantial decreased in plant growth attributes, photosynthetic pigment chlorophyll (Chl) and other photosynthetic parameters, and activity of enzymes involved in Chl biosynthesis (δ-aminolevulinic acid dehydratase), and photosynthetic processes (carbonic anhydrase and RuBisco). Also, S-deficiency enhanced reactive oxygen species (ROS) (superoxide and hydrogen peroxide) and lipid peroxidation (malondialdehyde) levels in tomato seedlings. Contrarily, foliar supplementation of NO to S-deficient seedlings resulted in considerably reduced ROS formation in leaves and roots, which alleviated low S-stress-induced lipid peroxidation. However, exogenous NO enhanced proline accumulation by increasing proline metabolizing enzyme (Δ-pyrroline-5-carboxylate synthetase) activity and also increased NO, hydrogen sulfide (a gasotransmitter small signaling molecule) and S uptake, and content of S-containing compounds (cysteine and reduced glutathione). Under S-limited conditions, NO improved S utilization efficiency of plants by upregulating the activity of S-assimilating enzymes (ATP sulfurylase, adenosine 5-phosphosulfate reductase, sulfide reductase and O-acetylserine (thiol) lyase). Under S-deprived conditions, improved S-assimilation of seedlings receiving NO resulted in improved redox homeostasis and ascorbate content through increased NO and S uptake. Application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy l-3-oxide (an NO scavenger) invalidated the effect of NO and again caused low S-stress-induced oxidative damage, confirming the beneficial role of NO in seedlings under S-deprived conditions. Thus, exogenous NO enhanced the tolerance of tomato seedlings to limit S-triggered oxidative stress and improved photosynthetic performance and S assimilation.
尽管已有大量关于一氧化氮（NO）在调节植物生长和减轻各种环境胁迫方面作用的报道，但它在硫（S）代谢中的参与仍知之甚少。因此，我们通过向 S 充足和 S 缺乏的幼苗叶片供应 NO，研究了 NO 在低 S 胁迫条件下番茄幼苗 S 吸收和 S 同化中的作用。S 饥饿的植物表现出植物生长特性、光合作用色素叶绿素（Chl）和其他光合作用参数以及参与 Chl 生物合成的酶（δ-氨基酮戊酸脱水酶）和光合作用过程（碳酸酐酶和 RuBisco）的活性显著下降。此外，S 缺乏会增加番茄幼苗中活性氧（ROS）（超氧阴离子和过氧化氢）和脂质过氧化（丙二醛）的水平。相反，向 S 缺乏的幼苗叶片补充 NO 会导致叶片和根系中 ROS 的形成明显减少，从而缓解低 S 胁迫诱导的脂质过氧化。然而，外源 NO 通过增加脯氨酸代谢酶（Δ-吡咯啉-5-羧酸合成酶）的活性来增加脯氨酸的积累，还增加了 NO、硫化氢（一种气体信号小分子）和 S 的吸收以及含 S 化合物（半胱氨酸和还原型谷胱甘肽）的含量。在 S 有限的条件下，NO 通过上调 S 同化酶（ATP 硫酸化酶、腺苷 5′-磷酸硫酸还原酶、硫化物还原酶和 O-乙酰丝氨酸（硫醇）裂解酶）的活性提高了植物对 S 的利用效率。在 S 剥夺条件下，接受 NO 的幼苗 S 同化的改善导致通过增加 NO 和 S 的吸收来改善氧化还原平衡和抗坏血酸含量。应用 2-（4-羧基苯基）-4,4,5,5-四甲基咪唑啉-1-氧基-3-氧化物（一种 NO 清除剂）使 NO 的作用无效，并再次导致低 S 胁迫诱导的氧化损伤，证实了 NO 在 S 剥夺条件下对幼苗的有益作用。因此，外源 NO 增强了番茄幼苗对限 S 触发的氧化应激的耐受性，并改善了光合作用性能和 S 同化。
