RPG: Molecular Tools for Studying Cotton Fiber Elongation

这是一项针对女性的研究计划拨款。细胞伸长取决于细胞壁的不可逆延伸以及细胞的水力传导和膨胀。吸收和生产渗透活性溶质维持膨胀是必要的，以维持细胞延长的时间周期。在细胞伸长过程中，协调细胞渗透调节和细胞壁延伸的细胞机制尚不清楚。棉纤维为研究调节纤维伸长的分子机制提供了良好的实验体系。棉花胚珠上的纤维是同步生长的，因此纤维的伸长也跟着发育。每根纤维都是一个细胞，这就消除了细胞分裂的复杂性。在棉纤维中，苹果酸盐是一种具有渗透活性的溶质，负责维持棉纤维的膨润。作为最终确定负责协调渗透调节和细胞壁松动的信号转导机制的第一步，PEP羧化酶的调节正在研究中，PEP羧化酶是纤维伸长过程中参与苹果酸盐合成的酶。纤维PEP羧化酶的五种异构体已经被鉴定出来，并通过它们在SDS聚丙烯酰胺凝胶上的电泳迁移率来区分。其中两种同工异构体在纤维伸长成熟过程中优先表达。这个项目的直接目的是确定这些不同的PEP羧化酶异构体是如何产生的。将采取两种互补的方法：(1)PEP羧化酶基因的分离和表征；(2)不同形式PEP羧化酶蛋白的纯化和表征。这些研究提供了必要的背景来定义这些不同的异构体在纤维伸长过程中的生理功能，更具体地说，这些异构体在纤维细胞的渗透调节中的作用。棉纤维在世界上很大一部分纺织品的生产中具有商业价值。纺纱系统的改进和生产速度的提高使纺织工业对棉纤维的要求越来越高。努力提高现有棉花种质的纤维质量，包括纤维的均匀性、强度和延伸性，对美国在世界市场上保持竞争力至关重要。利用现代分子工具确定控制纤维伸长的潜在调节机制，对未来育种和基因工程策略的发展具有重要意义，可以提高纤维的自旋值。

This is a research planning grant for women. Cell elongation depends on the irreversible extension of the cell wall and on hydraulic conductivity and turgor of the cell. The uptake and production of osmotically active solutes for maintenance of turgor is essential to maintain cell elongation for extended time periods. The cellular mechanisms that coordinate the osmoregulation of the cell and extension of the cell wall during cell elongation are poorly understood. Cotton fibers provide an excellent experimental system for studying molecular mechanisms regulating cellelongation. The fibers on the cotton ovule grow synchronously allowing fiber elongation to be followed developmentally. Each fiber is a single cell which eliminates the complications of cell division. In cotton fibers, malate is one of the osmotically active solutes responsible for the maintenance of turgor. As an initial step in ultimately identifying the signal transduction mechanism(s) responsible for coordinating osmoregulation and cell wall loosening, the regulation of PEP carboxylase, the enzyme involved in malate synthesis during fiber elongation, is being studied. Five isoforms of the fiber PEP carboxylase have been identified and are distinguishable by their electrophoretic mobility on SDS polyacrylamide gels. Two of these isoforms are preferentially expressed during maturation of fiber elongation. The immediate aim of this project is to determine how these different PEP carboxylase isoforms are produced. Two complimentary approaches will be taken: (1) isolation and characterization of the PEP carboxylase gene(s) and (2) purification and characterization of the different forms of the PEP carboxylase protein. These studies provide the necessary background to define thephysiological function of these different isoforms during fiber elongation and more specifically, the role of these isoforms in the osmoregulation of the fiber cell. The cotton fiber is commercially valuable in the manufacture of a large percentage of the world's textiles. Improved spinning systems and increased production speeds place increasing demands on the cotton fiber by the textile industry. Efforts to improve the fiber quality of existing cotton germplasm in terms of uniformity, strength and extensibility of the fiber are essential for the US to remain competitive in world markets. Defining the underlying regulatory mechanism(s) controlling fiber elongation utilizing modern molecular tools will be of immense importance in future development of breeding and genetic engineering strategies for improving the fiber's spin value.