Melatonin, widely found in various plants as a new antioxidant, could protect plants from various biotic and/or abiotic stresses, including salt stress. MzASMT 1 (KJ123721), a gene from Malus zumi Mats, is a key enzyme required for melatonin synthesis. However, whether the overexpression of MzASMT 1 could regulate the synthesis of melatonin and improve the salt tolerance in tobacco remains unknown. In this study, the overexpression of MzASMT 1 in tobacco increased the melatonin content, and the transgenic lines owned higher salt tolerance capacity. The transgenic lines overexpressing MzASMT 1 exhibited lower degree of leaf wilting; much more fresh weight; higher plant height; longer root; higher relative water content (RWC) of leaves, stem, and root; and higher chlorophyll content and Fv/Fm, which makes transgenic lines better adapt to salt stress. The transgenic lines also had higher accumulation of proline, lower accumulation of malondialdehyde (MDA), and improved antioxidant systems, which protected plants from cell damage and oxidative stress due to excess reactive oxygen species (ROS) accumulation under salt treatment. The transcription of salt response genes was much more highly activated in transgenic lines than in wild type under salt stress. The above results contributed to the understanding of functions for MzASMT 1 in tobacco under salt stress and provided a new choice for the application of MzASMT 1 in improving plant salt tolerance.

褪黑激素作为一种新的抗氧化剂广泛存在于各种植物中，可以保护植物免受各种生物和/或非生物胁迫，包括盐胁迫。MzASMT 1(KJ123721)，一个基因海棠Mats 是褪黑激素合成所需的关键酶。然而，是否过度表达MzASMT 1能否调节褪黑激素的合成并提高烟草的耐盐性仍不清楚。在本研究中，过度表达MzASMT 1烟草中褪黑激素含量增加，转基因品系具有较高的耐盐能力。转基因株系过表达MzASMT 1表现出较低程度的叶子枯萎；更多的鲜重；较高的株高；根较长；叶、茎和根的相对含水量（RWC）较高；更高的叶绿素含量和Fv/Fm，使转基因株系更好地适应盐胁迫。转基因品系还具有较高的脯氨酸积累、较低的丙二醛（MDA）积累和改进的抗氧化系统，从而保护植物免受盐处理下过量活性氧（ROS）积累导致的细胞损伤和氧化应激。在盐胁迫下，转基因品系中盐响应基因的转录比野生型中的激活程度高得多。上述结果有助于理解函数MzASMT 1为盐胁迫下烟草的应用提供了新的选择MzASMT 1提高植物的耐盐性。