Regulation and Functions of the Arabidopsis XET Gene Family

细胞壁是植物细胞的基本结构，控制着细胞的形状、大小和完整性，并在信号转导中发挥作用。修饰壁多糖的酶可能调节壁结构，从而在植物形态发生和生理中发挥重要作用。木葡聚糖内转糖基化酶（XETs）能够修饰细胞壁的主要成分，但这些酶的生理功能尚不清楚。植物中含有编码xet和xet相关蛋白的基因家族；这些酶的复杂性和保守性表明，这些酶可能在植物细胞生物学中起着至关重要的作用。通过提出的研究，将回答以下问题：1。拟南芥XET家族有多复杂？ XET初级结构有哪些独特和共有的特征？单个和多个xet丢失的生理后果是什么？xet在何时何地表达，蛋白质的模式和运动是什么？xet在生化活性上有哪些相似和/或不同之处？哪些结构特征可能对酶的功能很重要？由于存在一个基因家族，解剖xet的功能将需要一个广泛的，综合的方法。拟南芥的XET和XET相关基因将根据初级结构进行鉴定和分类。将寻找XET基因内的突变，以及突变表型在生长、发育和整体适应度方面的特征，以及壁特性和适应不同环境的能力。本文将阐明xet的表达模式和诱导行为。报告基因融合将能够确定组织、器官、细胞和发育特异性的表达。此外，报告子将用于确定蛋白质的定位和潜在运动。酶将用异源表达系统生产，并将评估和比较不同同工酶的性质，如底物偏好和反应条件。通过这项工作，拟南芥复杂的XET基因家族的调控和功能将被阐明。这些实验的完成将有助于深入了解细胞壁是如何形成、维持和修饰的，以及这些特性如何影响植物的整体适应性、发育和生理。

The cell wall is a fundamental structure of plant cells that controls cellular shape, size and integrity and also plays a role in signal transduction. The enzymes that modify wall polysaccharides are likely to regulate wall structure and thus play critical roles in plant morphogenesis and physiology. The xyloglucan endotransglycosylases (XETs) are capable of modifying a major component of the cell wall and yet the physiological functions of these enzymes are not understood. Plants harbor gene families that encode XETs and XET-related proteins; the complexity and conservation of these enzymes indicate that these enzymes likely carry out critically important roles in plant cell biology. The following questions will be answered through the proposed studies:1. How complex is the Arabidopsis XET family, and what are the unique and shared features of XET primary structures?2. What are the physiological consequences of the loss of single and multiple XETs?3. When and where are the XETs expressed, and what are the patterns and movements of the proteins?4. How are the XETs similar and/or distinct in biochemical activities and what structural features may be important for enzymatic function? Because of the presence of a gene family, dissection of the functions of XETs will require a broad-based, integrative approach. The XET and XET-related genes of Arabidopsis will be identified and classified based on primary structure. Mutations within XET genes will be sought and mutant phenotypes characterized with respect to growth, development and overall fitness, in addition to wall properties and ability to adapt to diverse environments. Expression patterns and induction behaviors of the XETs will be elucidated. Reporter gene fusions will enable determination of tissue, organ, cell and developmental specificity of expression. In addition, reporters will be used to define the localization and potential movements of the proteins. Enzymes will be produced with a heterologous expression system, and properties, such as substrate preferences and reaction conditions, will be assessed and compared among the different isozymes. Through this work, the regulation and functions of the complex XET gene family of Arabidopsis will be elucidated. Completion of these experiments will provide insight into how cell walls are formed, maintained and modified, and how these properties impact the overall fitness, development and physiology of plants.