Soil salinity is one of the major stresses that threatening the production and even survival of crops. NPR1 (nonexpressor of pathogenesis-related genes 1), traditionally considered to be involved in plant immunity by serving as a master regulator in salicylic acid signaling pathway, has been proved to play a critical role in regulating salt stress in plants. However, regarding the function of NPR1 in salt tolerance, most of researches focus on herbaceous plants, such as Arabidopsis and tobacco, whether NPR1 is functional in regulating salt stress in perennial woody plants has not been demonstrated. We report here that MdNPR1 positively regulates salt tolerance in apple (Malus domestica), an important perennial woody crop. MdNPR1 was inducible under salt treatment, and overexpressing MdNPR1 enhanced salt tolerance in both apple calli and shoots, accompanied by a lower level in both malondialdehyde (MDA) content and relative conductivity compared with wild-type (WT). In addition, ectopic expression of MdNPR1 also promoted salt tolerance in both Arabidopsis and tomato (Solanum lycopersicum L.). Results of physiological assays showed that content of reactive oxygen species (H2O2 and O2−) in MdNPR1-overexpressing apple seedlings and tomato were significantly lower than those found in the corresponding salt-treated WT plants. Moreover, expression of genes involved in facilitating Na+ efflux were elevated in MdNPR1 overexpressing apple seedlings, which might also contribute to the enhanced salt tolerance in transgenic apple seedlings. Therefore, our work determines that MdNPR1 is a positive regulator in manipulating salt stress tolerance in perennial woody plant apple, as well as in herbaceous plants Arabidposis and tomato.

中文翻译：

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MdNPR1 在苹果耐盐胁迫中起正调节因子的作用


土壤盐分是威胁农作物生产甚至生存的主要压力之一。NPR1 （nonexpresser of pathogenesis-related genes 1） 传统上被认为通过作为水杨酸信号通路的主调节因子参与植物免疫，已被证明在调节植物盐胁迫中起关键作用。然而，关于 NPR1 在耐盐性中的功能，大多数研究集中在草本植物上，如拟南芥和烟草，NPR1 是否在多年生木本植物中具有调节盐胁迫的功能尚未得到证实。我们在这里报道，MdNPR1 正向调节苹果 （Malus domestica） 的耐盐性，苹果是一种重要的多年生木本作物。MdNPR1 在盐处理下是可诱导的，过表达 MdNPR1 增强了苹果愈伤组织和芽的耐盐性，与野生型 （WT） 相比，丙二醛 （MDA） 含量和相对电导率水平较低。此外，MdNPR1 的异位表达也促进了拟南芥和番茄 （Solanum lycopersicum L.） 的耐盐性。生理学分析结果表明，过表达 MdNPR1 的苹果幼苗和番茄中活性氧（H2O2 和 O2−）的含量显著低于相应的盐处理 WT 植株中的活性氧含量。此外，在过表达 MdNPR1 的苹果幼苗中，参与促进 Na + 外排的基因表达升高，这也可能有助于增强转基因苹果幼苗的耐盐性。因此，我们的工作确定 MdNPR1 是操纵多年生木本植物苹果以及草本植物拟南芥和番茄耐盐胁迫性的正调节因子。