Function of Arabidopsis thaliana Proline Rich Proteins in Root Hairs and Guard Cells of Arabidopsis

植物细胞壁是一种动态结构，可以根据发育和环境信号进行修改。通过这种方式，细胞壁提供了结构信息，帮助维持植物生长过程中的细胞形态和功能。细胞壁的结构也会发生变化，以响应病原体的感染和胁迫，如干旱、高盐和低温，以帮助保护植物在自然环境中生长时免受生物和非生物胁迫。许多结构蛋白在细胞壁中的表达具有细胞型特异性，这表明这些蛋白在改变细胞壁结构以提供机械强度和帮助正确的壁组装方面发挥了新的作用。富含脯氨酸的蛋白(PRPS)是一个完整的结构细胞壁蛋白家族，其表达与许多植物系统的活跃生长有关。我们使用PRP启动子/GUS融合和表位标签相结合的方法来鉴定这些基因在拟南芥中的表达及其在特定细胞类型的壁上的定位。其中两个蛋白AtPRP1和AtPRP3在根毛生长的早期表达，但定位于根毛细胞壁的不同区域。这些结果表明，单个PRP基因成员可能在帮助建立根部毛细胞壁结构过程中发挥着不同的作用。此外，我们还发现AtPRP4在保卫细胞中表达，并定位于保卫细胞壁的内架。我们已经分离了这三种蛋白的几个T-DNA插入等位基因，并建议对这些突变体中与根毛和保卫细胞功能相关的功能缺失表型进行表征。此外，我们将检查表位标记的PRP序列在野生型和突变的PRP背景下在壁内交联化的能力。结合这些实验方法，这些实验方法应该为单个AtPRP编码的氨基酸序列的性质提供新的见解，这些氨基酸序列足以使它们在细胞壁中定向定位，并在细胞外基质中不溶解。鉴定结构细胞壁蛋白在定义细胞类型特定基质结构中的功能是鼓励以一种让植物在不利环境中生长的方式改变植物细胞壁的重要的第一步。我们已经证明，AtPRP蛋白参与决定保卫细胞和树冠细胞的细胞壁结构，这两种细胞类型对营养吸收和维持生长过程中的水分平衡至关重要。进一步分析这些蛋白质的功能可能会让我们设计出新的机制来促进植物在水分和/或营养限制条件下的生长。

The plant cell wall is a dynamic structure that can be modified in responseto developmental and environmental signals. In this manner, the cell wallprovides structural information that helps maintain cellular form andfunction during plant growth. The structure of the cell wall also changesin response to pathogen infection and stresses, such as drought, high saltand cold temperature, in a manner that helps protect plants from biotic andabiotic stresses when grown in natural environments. Expression of many ofthe structural proteins in the wall have been shown to be cell-typespecific, suggesting that these proteins play novel roles in modifying cellwall structure in order to provide mechanical strength and assist in properwall assembly.Proline-rich proteins (PRPs) represent an integral family of structuralcell wall proteins whose expression has been linked to active growth in anumber of plant systems. We have used a combination of PRP promoter/GUSfusions and epitope-tagging to characterize the expression of these genesin arabidopsis and their localization to the walls of specific cell types.Two of these proteins, AtPRP1 and AtPRP3, are expressed during the earlystages of root hair outgrowth but are localized within different regions ofthe root hair cell wall. These results suggest that individual PRP genefamily members may play distinct roles in helping to establish root haircell wall structure during wall assembly. In addition, we have shown thatAtPRP4 is expressed in guard cells and localizes to the inner shelf of theguard cell wall. We have isolated several T-DNA insertion alleles forthese three proteins and we propose to characterize the loss-of-functionphenotypes in these mutants associated with root hair and guard cellfunction. In addition, we will examine the ability of epitope-tagged PRPsequences to become cross-linked within the wall in wild type and mutantPRP backgrounds. In combination, these experimental approaches shouldprovide new insight into the nature of the amino acid sequences encodedwithin individual AtPRPs that are sufficient for their targetedlocalization within the cell wall and their insolubilization within theextracellular matrix.Identification of the function of structural cell wall proteins in definingcell-type specific matrix structures is an important first step in ourability to modify the cell walls of plants in a manner that will let themgrow in adverse environments. We have shown that the AtPRP proteinsparticipate in determining cell wall structure in guard cells and roothairs, two cell types that are crucial for nutrient uptake and maintenanceof water balance during growth. Further analysis of the function of theseproteins may allow us to devise novel mechanisms for enhancing plant growthunder conditions of water and/or nutrient limitation.