Abscisic acid (ABA) induces chlorophyll degradation and leaf senescence; however, the molecular mechanism remains poorly understood, especially in woody plants. In this study, we found that MdABI5 plays an essential role in the regulation of ABA‐triggered leaf senescence in Malus domestica (apple). Through yeast screening, three transcription factors, MdBBX22, MdWRKY40 and MdbZIP44, were found to interact directly with MdABI5 in vitro and in vivo. Physiological and biochemical assays showed that MdBBX22 delayed leaf senescence in two pathways. First, MdBBX22 interacted with MdABI5 to inhibit the transcriptional activity of MdABI5 on the chlorophyll catabolic genes MdNYE1 and MdNYC1, thus negatively regulating chlorophyll degradation and leaf senescence. Second, MdBBX22 interacted with MdHY5 to interfere with the transcriptional activation of MdHY5 on MdABI5, thereby inhibiting the expression of MdABI5, which also contributed to the delay of leaf senescence. MdWRKY40 and MdbZIP44 were identified as positive regulators of leaf senescence. They accelerated MdABI5‐promoted leaf senescence through the same regulatory pathways, i.e., interacting with MdABI5 to enhance the transcriptional activity of MdABI5 on MdNYE1 and MdNYC1. Taken together, our results suggest that MdABI5 works with its positive or negative interaction partners to regulate ABA‐mediated leaf senescence in apple, in which it acts as a core regulator. The antagonistic regulation pathways ensure that plants respond to external stresses flexibly and efficiently. Our results provide a concept for further study on the regulation mechanisms of leaf senescence.

中文翻译：

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MdABI5与其相互作用伙伴合作调节苹果脱落酸介导的叶片衰老

脱落酸 (ABA) 诱导叶绿素降解和叶片衰老；然而，分子机制仍然知之甚少，尤其是在木本植物中。在这项研究中，我们发现，MdABI5起在ABA触发叶片衰老的调节具有重要作用海棠斯蒂卡（苹果）。通过酵母筛选，发现三种转录因子 MdBBX22、MdWRKY40 和 MdbZIP44在体外和体内与 MdABI5 直接相互作用。生理和生化分析表明，MdBBX22 通过两种途径延缓叶片衰老。首先，MdBBX22 与 MdABI5 相互作用以抑制 MdABI5 对叶绿素分解代谢基因MdNYE1和MdNYC1的转录活性，从而负调节叶绿素降解和叶片衰老。其次，MdBBX22与MdHY5相互作用，干扰MdHY5对MdABI5的转录激活，从而抑制MdABI5的表达，这也有助于延缓叶片衰老。MdWRKY40 和 MdbZIP44 被鉴定为叶片衰老的正调节因子。他们通过相同的调控途径加速 MdABI5 促进的叶片衰老，即与 MdABI5 相互作用以增强 MdABI5 对MdNYE1和MdNYC1的转录活性. 综上所述，我们的结果表明 MdABI5 与其正或负相互作用伙伴一起调节 ABA 介导的苹果叶片衰老，并在其中发挥核心调节作用。拮抗调节途径确保植物灵活有效地应对外部胁迫。我们的研究结果为进一步研究叶片衰老的调控机制提供了一个概念。