Molecular Cell Biology, Botanical Institute, Karlsruhe Institute of Technology, Fritz-Haber-Weg 4, 76133 Karlsruhe, Germany.
Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510301, China.
Int J Mol Sci. 2022 Aug 2;23(15):8593. doi: 10.3390/ijms23158593.
The complexity of auxin signaling is partially due to multiple auxin receptors that trigger differential signaling. To obtain insight into the subcellular localization of auxin-binding sites, we used fluorescent auxin analogs that can undergo transport but do not deploy auxin signaling. Using fluorescent probes for different subcellular compartments, we can show that the fluorescent analog of 1-naphthaleneacetic acid (NAA) associates with the endoplasmic reticulum (ER) and tonoplast, while the fluorescent analog of indole acetic acid (IAA) binds to the ER. The binding of the fluorescent NAA analog to the ER can be outcompeted by unlabeled NAA, which allows us to estimate the affinity of NAA for this binding site to be around 1 μM. The non-transportable auxin 2,4-dichlorophenoxyacetic acid (2,4-D) interferes with the binding site for the fluorescent NAA analog at the tonoplast but not with the binding site for the fluorescent IAA analog at the ER. We integrate these data into a working model, where the tonoplast hosts a binding site with a high affinity for 2,4-D, while the ER hosts a binding site with high affinity for NAA. Thus, the differential subcellular localization of binding sites reflects the differential signaling in response to these artificial auxins.
生长素信号的复杂性部分归因于多种生长素受体，这些受体触发不同的信号转导。为了深入了解生长素结合位点的亚细胞定位，我们使用了荧光生长素类似物，这些类似物可以进行运输，但不会引发生长素信号转导。使用不同亚细胞区室的荧光探针，我们可以表明，1-萘乙酸（NAA）的荧光类似物与内质网（ER）和液泡膜结合，而吲哚乙酸（IAA）的荧光类似物与 ER 结合。荧光 NAA 类似物与 ER 的结合可以被未标记的 NAA 竞争，这使我们能够估计 NAA 与该结合位点的亲和力约为 1 μM。非运输性生长素 2,4-二氯苯氧乙酸（2,4-D）干扰荧光 NAA 类似物在液泡膜上的结合位点，但不干扰荧光 IAA 类似物在 ER 上的结合位点。我们将这些数据整合到一个工作模型中，其中液泡膜上有一个与 2,4-D 具有高亲和力的结合位点，而 ER 上有一个与 NAA 具有高亲和力的结合位点。因此，结合位点的差异亚细胞定位反映了对这些人工生长素的差异信号转导。
