Auxin is a major plant growth regulator, but current models on auxin perception and signaling cannot explain the whole plethora of auxin effects, in particular those associated with rapid responses. A possible candidate for a component of additional auxin perception mechanisms is the AUXIN BINDING PROTEIN 1 (ABP1), whose function in planta remains unclear. Here we combined expression analysis with gain- and loss-of-function approaches to analyze the role of ABP1 in plant development. ABP1 shows a broad expression largely overlapping with, but not regulated by, transcriptional auxin response activity. Furthermore, ABP1 activity is not essential for the transcriptional auxin signaling. Genetic in planta analysis revealed that abp1 loss-of-function mutants show largely normal development with minor defects in bolting. On the other hand, ABP1 gain-of-function alleles show a broad range of growth and developmental defects, including root and hypocotyl growth and bending, lateral root and leaf development, bolting, as well as response to heat stress. At the cellular level, ABP1 gain-of-function leads to impaired auxin effect on PIN polar distribution and affects BFA-sensitive PIN intracellular aggregation. The gain-of-function analysis suggests a broad, but still mechanistically unclear involvement of ABP1 in plant development, possibly masked in abp1 loss-of-function mutants by a functional redundancy.

中文翻译：

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生长素结合蛋白1在拟南芥中的发育作用

生长素是一种主要的植物生长调节剂，但目前关于生长素感知和信号传导的模型无法解释全部过多的生长素效应，尤其是那些与快速反应相关的效应。其他生长素感知机制的一个组成部分的可能候选者是 AUXIN BINDING PROTEIN 1 (ABP1)，其在植物中的功能仍不清楚。在这里，我们将表达分析与功能获得和损失方法相结合，以分析 ABP1 在植物发育中的作用。ABP1 显示出广泛的表达，很大程度上与转录生长素反应活性重叠，但不受其调节。此外，ABP1 活性对于转录生长素信号传导不是必需的。足底遗传分析表明，abp1 功能丧失突变体显示出大部分正常发育，抽薹有轻微缺陷。另一方面，ABP1 功能获得等位基因表现出广泛的生长和发育缺陷，包括根和下胚轴的生长和弯曲、侧根和叶的发育、抽薹以及对热应激的反应。在细胞水平上，ABP1 功能获得导致生长素对 PIN 极性分布的影响受损，并影响 BFA 敏感的 PIN 细胞内聚集。功能获得分析表明 ABP1 在植物发育中的广泛但机制上仍不清楚，可能通过功能冗余掩盖了 abp1 功能丧失突变体。ABP1 功能获得导致生长素对 PIN 极性分布的影响受损，并影响 BFA 敏感的 PIN 细胞内聚集。功能获得分析表明 ABP1 在植物发育中的广泛但机制上仍不清楚，可能通过功能冗余掩盖了 abp1 功能丧失突变体。ABP1 功能获得导致生长素对 PIN 极性分布的影响受损，并影响 BFA 敏感的 PIN 细胞内聚集。功能获得分析表明 ABP1 在植物发育中的广泛但机制上仍不清楚，可能通过功能冗余掩盖了 abp1 功能丧失突变体。