School of Life Sciences, University of Warwick, Coventry CV4 7AS, United Kingdom.
Cold Spring Harb Perspect Biol. 2021 Dec 1;13(12):a039909. doi: 10.1101/cshperspect.a039909.
The auxin-binding protein 1 (ABP1) has endured a history of undulating prominence as a candidate receptor for this important phytohormone. Its capacity for binding auxin has not been in doubt, a feature adequately explained by its crystal structure, but any relevance of this to auxin signaling and plant development has been far more demanding to define. Over its research lifetime, it has been associated with many auxin-induced activities, including ion fluxes across the plasma membrane, rearrangement of the cytoskeleton and cell shape, and the abundance of PIN proteins at the plasma membrane via control of endocytosis, all of which required its presence in the apoplast. Yet, ABP1 has a KDEL sequence that targets it to the endoplasmic reticulum, where most of it remains. This mismatch has been more than adequately compensated for by the need for an auxin receptor to account for responses far too rapid to be executed through transcription and translation and the TIR1/AuxIAA coreceptor system. However, discoveries showing that null mutants are not compromised for auxin signaling or development, that TIR1 or AFB1 are necessarily involved with very rapid responses at the plasma membrane, and that these rapid responses are mediated with intracellular auxin all suggest that ABP1's auxin-binding capacity is not physiologically relevant. Nevertheless, ABP1 is ubiquitous in higher plants and throughout plant tissues. We need to complete its history by defining its function inside plant cells.
生长素结合蛋白 1（ABP1）作为这种重要植物激素的候选受体，其历史地位经历了起起落落。其结合生长素的能力毋庸置疑，其晶体结构充分解释了这一点，但任何与生长素信号转导和植物发育相关的功能都更难以定义。在其研究生涯中，它与许多生长素诱导的活动有关，包括跨质膜的离子流、细胞骨架和细胞形状的重排，以及通过内吞作用控制质膜上 PIN 蛋白的丰度，所有这些都需要它存在于质外体中。然而，ABP1 具有 KDEL 序列，使其靶向内质网，其中大部分仍然存在。这种不匹配已经被生长素受体的需求所充分补偿，生长素受体需要解释远快于转录和翻译的反应，以及 TIR1/AuxIAA 核心受体系统。然而，发现表明，缺失突变体在生长素信号转导或发育方面没有受到影响，TIR1 或 AFB1 必然与质膜上的快速反应有关，这些快速反应是通过细胞内生长素介导的，这一切都表明 ABP1 的生长素结合能力在生理上并不相关。尽管如此，ABP1 在高等植物和整个植物组织中无处不在。我们需要通过定义其在植物细胞内的功能来完成它的历史。
