Cell Wall Associated, Receptor Protein Kinases

细胞壁相关受体蛋白激酶

• 批准号: 0090527
• 负责人: Bruce Kohorn
• 金额: $ 10万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-05-01 至 2002-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0090527&HistoricalAwards=false
• 关键词: Cell; Wall; Associated; Receptor; Protein

Cell walls are carbohydrate and protein structures that surround and separate plant cells.As plant cells expand in a regulated fashion they must necessarily modify and enlargetheir cell walls to permit the subsequent increase in volume. The cell wall itself mightinfluence this expansion process. Thus the cell has the potential to influence almost everyaspect of plant function simply because of its position and physical properties. For thisreason many have speculated on its role in a plant's development and response to theoutside world. Cell growth can occur in many dimensions, such as the polarizedexpansion of a pollen tube tip, the creation of elongated cells characteristic of manyvegetative tissues, the establishment of a meristem, or even the jigsaw-like arrangementof cells at the leaf surface. Currently the understanding of how cell wall architecture iscoordinated with programmed and hormone regulated cell expansion events duringdevelopment is not well understood in angiosperms.Recent studies have identified a number of proteins at the cell surface that coulddirectly regulate cell wall functions, and the Cell Wall Associated Kinases, or WAKs, areamong these. There are five cell wall associated kinases in Arabidopsis andrepresentatives in other angiosperm families. WAKs each have a cytoplasmicserine/threonine protein kinase domain, span the plasma membrane and extend a domaininto the cell wall. WAKs physically link the plasma membrane to the carbohydrate matrixand are unique in that they have the potential to directly signal cellular events throughtheir kinase domain.The WAK extracellular domain is variable between the five isoforms, and collectivelythe family is expressed in all organs. WAK1 and WAK2 are the most ubiquitously andabundantly expressed of the five tandemly arrayed genes, and their messages are presentin vegetative meristems, junctions of organ types, and areas of cell expansion. They arealso induced by pathogen infection and wounding. The WAK1 but not WAK2 cell walldomain binds to a glycine rich protein (GRP) of the cell wall in in vitro assays. WAK1and GRP can be co-immunoprecipitated from leaf or seedling extracts, and this WAK isphosphorylated. Recent experiments demonstrate that antisense WAK expression leadsto the loss of cell expansion, and preliminary results indicate that antisense GRPproduction causes an enhancement of cell expansion (and eventual cell death). Thus GRPmay be a negative regulator of WAK activity. A large amount of WAK is also covalentlylinked to pectin, and most of WAK that is bound to pectin is also phosphorylated. Thedata support a model where WAK1 is bound to GRP as a phosphorylated kinase, and alsobinds to pectin. How WAKs are involved in signaling from the pectin extracellular matrixin coordination with GRPs will be key to the understanding of the cell wall's role in cellgrowth.WAKs are poised to provide a direct signal from the cell wall to the cytoplasm of manycell types during the development of Arabidopsis. In order to characterize theassociations and roles of GRPs and WAKs in plants it will be necessary to generateadditional (partial) loss of function alleles of the two predominant WAKs and of GRP.These alleles can then be used to determine the relationship of WAK mediated cellexpansion to other known signaling pathways. WAK kinase substrates will be alsoidentified and used to assay the activation of WAK by wall components anddevelopmental cues, and eventually mutant alleles of these substrates will help in theanalysis of WAKs and cell elongation. The goal is to understand how WAKs inassociation with GRP and pectins regulate cytoplasmic components so that the cell wallis coordinated with processes of cell growth.

细胞壁是包围和分离植物细胞的碳水化合物和蛋白质结构。当植物细胞以一种受调节的方式扩张时，它们必须修改和扩大细胞壁，以允许随后的体积增加。细胞壁本身可能影响这种扩张过程。因此，仅仅因为细胞的位置和物理性质，它就有可能影响植物功能的几乎所有方面。由于这个原因，许多人猜测它在植物的发育和对外界的反应中所起的作用。细胞生长可以发生在许多方面，例如花粉管尖端的极化扩张，许多营养组织特有的细长细胞的产生，分生组织的建立，甚至是叶表面细胞的锯齿状排列。目前对被子植物细胞壁结构如何与程序化和激素调节的细胞扩增事件协调的理解尚不清楚。最近的研究已经在细胞表面发现了许多可以直接调节细胞壁功能的蛋白质，细胞壁相关激酶（WAKs）就是其中之一。在拟南芥和其他被子植物家族中有5种细胞壁相关激酶。每个WAKs都有一个细胞质丝氨酸/苏氨酸蛋白激酶结构域，跨越质膜并将结构域延伸到细胞壁。WAKs在物理上将质膜与碳水化合物基质连接起来，并且它们具有通过其激酶结构域直接传递细胞事件信号的潜力，这是独一无二的。WAK胞外结构域在五种亚型之间是可变的，并且该家族在所有器官中都有表达。WAK1和WAK2是五个串联排列基因中最普遍和最丰富表达的，它们的信息存在于营养分生组织、器官类型的连接和细胞扩张区域。它们也可由病原体感染和损伤引起。体外实验表明，WAK1细胞壁结构域与细胞壁富甘氨酸蛋白（GRP）结合，而WAK2细胞壁结构域与之不结合。wak1和GRP可以从叶片或幼苗提取物中共免疫沉淀，并且该wak1被磷酸化。最近的实验表明，反义WAK表达导致细胞扩增丧失，初步结果表明，反义grp的产生导致细胞扩增增强（最终导致细胞死亡）。因此grp可能是WAK活性的负调节因子。大量的WAK也与果胶共价连接，并且大多数与果胶结合的WAK也被磷酸化。数据支持WAK1作为磷酸化激酶与GRP结合的模型，也与果胶结合。WAKs如何参与果胶胞外基质蛋白与grp协调的信号传递将是理解细胞壁在细胞生长中的作用的关键。在拟南芥的发育过程中，WAKs可以提供细胞壁到细胞质的直接信号。为了表征GRP和wak在植物中的关联和作用，有必要产生两个主要wak和GRP的功能等位基因的额外（部分）损失。这些等位基因可以用来确定WAK介导的细胞扩增与其他已知信号通路的关系。WAK激酶底物也将被鉴定并用于分析壁面成分和发育线索对WAK的激活，最终这些底物的突变等位基因将有助于分析WAK和细胞伸长。目的是了解与GRP和果胶相关的WAKs如何调节细胞质成分，从而使细胞壁与细胞生长过程协调一致。