Nitrate is a major nitrogen resource for plant growth and development and acts as both a crucial nutrient and a signaling molecule for plants; hence, understanding nitrate signaling is important for crop production. Abscisic acid (ABA) has been demonstrated to be involved in nitrate signaling, but the underlying mechanism is largely unknown in apple. In this study, we found that exogenous ABA inhibited the transport of nitrate from roots to shoots in apple, and the transcription of the nitrate transporter MdNRT1.5/MdNPF7.3 was noticeably reduced at the transcriptional level by ABA, which inhibited the transport of nitrate from roots to shoots. Then, it was found that the ABA-responsive transcription factor MdABI5 bound directly to the ABRE recognition site of the MdNRT1.5 promoter and suppressed its expression. Overexpression of MdABI5 inhibited ABA-mediated transport of nitrate from roots to shoots. Overall, these results demonstrate that MdABI5 regulates the transport of nitrate from roots to shoots partially by mediating the expression of MdNRT1.5, illuminating the molecular mechanism by which ABA regulates nitrate transport in apple.

中文翻译：

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MdABI5 转录因子与 MdNRT1.5/MdNPF7.3 启动子相互作用以微调硝酸盐从苹果根部到枝条的转运

硝酸盐是植物生长发育的主要氮源，既是植物的重要营养素，又是信号分子；因此，了解硝酸盐信号对作物生产很重要。脱落酸 (ABA) 已被证明与硝酸盐信号传导有关，但苹果的潜在机制在很大程度上是未知的。在这项研究中，我们发现外源 ABA 抑制了硝酸盐从根部向苹果枝条的转运，以及硝酸盐转运蛋白的转录。MdNRT1.5/MdNPF7.3ABA在转录水平上显着降低，从而抑制硝酸盐从根部到芽的​​运输。然后，发现 ABA 反应转录因子 MdABI5 直接结合到MdNRT1.5启动子并抑制其表达。过度表达MdABI5抑制 ABA 介导的硝酸盐从根部到芽的​​转运。总体而言，这些结果表明 MdABI5 部分通过介导MdNRT1.5，阐明了 ABA 调节苹果硝酸盐转运的分子机制。