Although melatonin has been reported to function as a stress signaling molecule, not much information is available on the biochemical and molecular events associated with probable melatonin-hydrogen sulfide crosstalk in plants. Present work provides evidence on the role of melatonin in the modulation of H2S homoeostasis during NaCl stress in dark-grown tomato (Solanum lycopersicum L. var. cherry) seedlings. NaCl stress (120 mM) inhibits hypocotyl elongation, promotes primary root growth and enhances electrolytic leakage from tomato seedlings. Treatment with H2S donor (100 µM; NaHS) tends to reverse these effects, all the more so (additive effect) in the presence of melatonin. NaCl stress and exogenous melatonin (30 µM) treatments modulate endogenous H2S accumulation and positively upregulate the activity of L-cysteine desulfhydrase (L-DES; EC 4.4.1.15; cytosolic). Melatonin has been observed to temporally modulate the activity of specific isoforms of H2S biosynthesizing enzyme, L-DES in seedling cotyledons. Zymographic analysis of L-DES isoforms in tomato seedling cotyledons has provided novel findings in plant system. Melatonin treatment decreases H2S accumulation in NaCl-stressed seedling cotyledons which is accompanied by a contrasting increase in L-DES activity. Melatonin, therefore, regulates endogenous H2S concentration in seedling cotyledons (NaCl treated), thus indicating the role of H2S catabolism pathways in H2S homoeostasis. Present findings thus reveal that exogenous melatonin modulates early H2S signaling in cotyledons of tomato seedlings subjected to NaCl stress. Furthermore, exogenous melatonin and H2S in combination (additive effect) ameliorate NaCl stress-induced growth changes in tomato seedlings.

中文翻译：

---

外源褪黑激素调节盐胁迫番茄（Solanum lycopersicum L. var.cherry）幼苗子叶中的内源性 H2S 稳态和 L-半胱氨酸脱硫酶活性

尽管据报道褪黑激素可用作应激信号分子，但关于与植物中可能的褪黑激素-硫化氢串扰相关的生化和分子事件的信息并不多。目前的工作提供了关于褪黑激素在暗生长番茄（Solanum lycopersicum L. var.cherry）幼苗中 NaCl 胁迫期间调节 H2S 稳态的作用的证据。NaCl 胁迫 (120 mM) 抑制下胚轴伸长，促进主根生长并增强番茄幼苗的电解泄漏。用 H2S 供体 (100 µM; NaHS) 处理往往会逆转这些影响，在褪黑激素存在的情况下更是如此（附加效应）。NaCl 胁迫和外源性褪黑激素 (30 µM) 处理可调节内源性 H2S 积累并正上调 L-半胱氨酸脱硫酶 (L-DES; EC 4.4. 1.15; 胞质）。已观察到褪黑激素可暂时调节幼苗子叶中 H2S 生物合成酶 L-DES 的特定同工型的活性。番茄幼苗子叶中 L-DES 同种型的酶谱分析为植物系统提供了新的发现。褪黑激素处理减少了 NaCl 胁迫的幼苗子叶中 H2S 的积累，同时伴随着 L-DES 活性的相反增加。因此，褪黑激素调节幼苗子叶（NaCl 处理）中的内源 H2S 浓度，从而表明 H2S 分解代谢途径在 H2S 稳态中的作用。因此，目前的研究结果表明，外源性褪黑激素调节受到 NaCl 胁迫的番茄幼苗子叶中的早期 H2S 信号传导。此外，