Molecular mechanisms of auxin response

项目总结 蛋白质的可逆丝氨酸/苏氨酸磷酸化在许多 细胞过程。2C型蛋白磷酸酶(PP2Cs)是一类主要的丝氨酸/苏氨酸磷酸酶 (PPase)，几个人类PP2C的缺陷与癌症、糖尿病、心血管疾病有关 疾病、神经紊乱和压力信号。然而，在理解PP2C如何 酶的活性受到调节，以及PP2C控制下的特定蛋白质和过程是什么。在植物中， PP2C.D PPase通过抑制细胞扩张来抑制器官生长。这在一定程度上是通过以下方式实现的 质膜H+-ATPase的关键调节亚磷酸盐的去磷酸化。增长 激素生长素通过诱导小生长素上调RNA(SAUR)基因的表达来刺激细胞扩张，该基因 编码与PP2C.D PPase结合的新蛋白，以抑制酶活性。这样做的长期目标是 项目是彻底了解生长素介导的植物控制的分子机制 成长和发展。更具体地说，本提案中描述的工作将确定监管机构和 SAUR-PP2C.D信号枢纽下游效应分子参与生长素介导的细胞扩张 将体积变化与不同的细胞过程相结合，以产生协调的生长反应。 磷蛋白质组学研究发现&gt；140蛋白表现出改变的磷酸化反应 生长素。该数据集与受SAUR过度表达影响的磷蛋白有很大重叠，暗示 在细胞扩张过程中，SAUR-PP2C.D模块作为生长素磷酸化的主要调节因子。使用 功能强大的模式植物拟南芥的遗传系统，建议进行的研究将探讨其功能 部分候选磷蛋白在生长素诱导的生长中的作用及其与SAUR的调控相互作用 PP2C.D模块。还将详细分析生长素对质膜H+-ATPase活性的调节。 生长素通过抑制PP2C.D活性抑制H+-ATPase去磷酸化 TMk1和包括WNK同源基因在内的附加激酶促进ATPase磷酸化的激活 以及与哺乳动物细胞大小控制有关的SPAK/OSR激酶。所有这些激酶都与一个 另一种是PP2C.D PPase，研究将解决激酶和磷酸酶活性是如何 相互协调、相互规范。这项工作将阐明PP2C的功能和调控机制。 识别调节细胞扩张的PP2C.D效应器，并阐明生长素如何协调不同的细胞 控制单元格大小的过程。鉴于PP2C功能在各个王国和宇宙中的守恒 细胞大小控制过程，项目发现将产生广泛影响，包括对人类的影响 发展和疾病。此外，由于人类依赖植物提供食物、纤维和 制药方面，拟议的研究将阐明SAUR-PP2C.D调控对植物生长的控制 模块，并促进操纵植物生长的新战略，以造福人类健康。

PROJECT SUMMARY Reversible serine/threonine phosphorylation of proteins plays an essential regulatory function in numerous cellular processes. Type 2C protein phosphatases (PP2Cs) comprise a major class of Ser/Thr phosphatases (PPases), and defects in several human PP2Cs have been implicated in cancer, diabetes, cardiovascular disease, neural disorders, and stress signaling. However, major gaps exist in understanding how PP2C enzyme activity is regulated and what specific proteins and processes are under PP2C control. In plants, PP2C.D PPases inhibit organ growth by repressing cell expansion. In part, this is accomplished by dephosphorylation of a key regulatory phosphosite of plasma membrane (PM) H+-ATPases. The growth hormone auxin stimulates cell expansion by inducing expression of Small Auxin Up RNA (SAUR) genes, which encode novel proteins that bind to PP2C.D PPases to inhibit enzymatic activity. The long-term goal of this project is to thoroughly understand the molecular mechanisms underlying auxin-mediated control of plant growth and development. More specifically, the work described in this proposal will identify regulators and downstream effectors of SAUR-PP2C.D signaling hubs involved in auxin-mediated cell expansion and the integration of volumetric changes with diverse cellular processes to yield a coordinated growth response. Phosphoproteomic studies have identified >140 proteins exhibiting altered phosphorylation in response to auxin. This dataset overlaps substantially with phosphoproteins affected by SAUR overexpression, implicating SAUR-PP2C.D modules as major regulators of the auxin phosphorylome during cell expansion. Using the powerful genetic system of the model plant Arabidopsis, the proposed studies will investigate the functional roles of select phosphoprotein candidates in auxin-induced growth and their regulatory interactions with SAUR- PP2C.D modules. Detailed analysis of auxin’s regulation of PM H+-ATPase activity will also be conducted. Auxin both inhibits H+-ATPase dephosphorylation via SAUR repression of PP2C.D activity and stimulates activation by promoting ATPase phosphorylation by TMK1 and additional kinases, including orthologs of WNK and SPAK/OSR kinases implicated in mammalian cell size control. All of these kinases interact with one another and PP2C.D PPases, and research will address how kinase and phosphatase activities are coordinated and mutually regulated. This work will elucidate PP2C functions and regulatory mechanisms, identify PP2C.D effectors that modulate cell expansion, and illuminate how auxin coordinates diverse cellular processes to control cell size. Given the conservation of PP2C function across kingdoms and the universal process of cell size control, project findings will have broad impact, including implications into human development and disease. Further, as humans depend on plants for sources of food, fiber, and pharmaceuticals, the proposed studies will elucidate plant growth control by SAUR-PP2C.D regulatory modules and facilitate novel strategies for manipulating plant growth to benefit human health.