Analysis of APP1 Regulation of Auxin and Jasmonic Acid Signalling in Arabidopsis

在植物中，TIR1/AFB受体蛋白通过刺激生长素依赖基因转录的AUX/IAA抑制因子的蛋白水解降解来调节对植物激素生长素的应答。几乎所有的生长素反应都涉及到TIR1/ afb、AUX/IAAs和生长素应答转录激活因子的特定配对。对脯氨酸顺式反式异构酶（PPIase）抑制剂juglone的实验表明，PPIase可能以生长素不依赖的方式控制AUX/IAA的降解速率。最近，研究人员发现拟南芥APP1具有核桃素敏感的x -脯氨酸氨基肽酶和PPIase活性，通过AUX/IAA蛋白的相互作用域直接与它们相互作用。与野生型植物相比，这些app1突变体表现出生长素敏感性降低；在生长素处理后，它们的伸长生长减少，生长素反应基因和合成报告基因的表达急剧下降。APP1活性的增加导致生长素响应基因的表达和生长的增加，与低浓度生长素处理的植物相似。该项目的总体目标是阐明APP1在TIR1/ afb介导的生长素信号传导中的作用。该项目的具体目标如下：1)该项目将确定APP1的哪种酶活性调节生长素反应。研究人员假设PPIase活性介导了estir1 -AUX/IAA的相互作用，而蛋白水解活性有助于随后的AUX/IAA加工。2)本项目将确定APP1在生长素反应通路中的作用。这项工作的基础模型提出，APP1稳定AUX/IAAs的相互作用域以促进TIR1的结合。该项目有望描述植物激素信号的一个未被认识的全球组成部分。该项目具有变革性，因为它将有助于确定在AtAPP1中发现的PPIase活性是否存在于其他物种的APP同源物中，以及APP是否可能在动物和真菌信号机制中发挥先前未被考虑的作用。该项目还将包括来自PI和Wendy Peer博士运营的暑期本科生研究项目的学生，该项目从缺乏服务的人群中招募学生进入生命科学领域。

Project Abstract In plants, the TIR1/AFB receptor proteins regulate responses to the plant hormone auxin by stimulating the proteolytic degradation of AUX/IAA repressors of auxin-dependent gene transcription. Almost all auxin responses have been shown to involve specific pairings of TIR1/AFBs, AUX/IAAs, and auxin-responsive transcriptional activators. Experiments with the prolyl cis-trans isomerase (PPIase) inhibitor juglone suggest that a PPIase may control the rate of AUX/IAA degradation in an auxin-independent manner. Recently, the investigators have discovered that Arabidopsis APP1, which possesses juglone-sensitive X-prolyl aminopeptidase and PPIase activities, directly interacts with AUX/IAA proteins via their interaction domains. As compared to wild type plants, these app1 mutants exhibit reduced auxin sensitivity; they have reduced elongation growth, as well as sharply decreased expression of auxin responsive genes and synthetic reporters after auxin treatment. Increased APP1 activity results in increased auxin-responsive gene expression and growth similar to that seen in plants treated with low concentrations of auxin. The overall goal of the project is to elucidate the role of APP1 in TIR1/AFB-mediated auxin signaling. The specific objectives of the project are as follows. 1) The project will determine which enzymatic activity of APP1 regulates auxin responses. The investigators hypothesize that the PPIase activity mediatesTIR1-AUX/IAA interactions and that the proteolytic activity contributes to subsequent AUX/IAA processing. 2) The project will determine the function of APP1 in the auxin response pathway. The model underlying the work proposes that APP1 stabilizes the interaction domain of AUX/IAAs to promote TIR1 binding. This project is expected to characterize an unrecognized global component of plant hormone signaling. The project is transformative, as it will help determine whether the PPIase activity discovered in AtAPP1 is found in APP orthologs from other species and whether APPs may play a previously uncontemplated role in animal and fungal signaling mechanisms. The project will also involve students from a summer undergraduate research program run by the PI and Dr. Wendy Peer that recruits students into the life sciences from underserved populations.