UVM Theses and Dissertations
Format:
Print
Author:
Carter, Jamie Paul
Dept./Program:
Microbiology and Molecular Genetics
Year:
2011
Degree:
PhD
Abstract:
Plant cells are surrounded by a complex interwoven matrix of carbohydrate and protein components. Classically, the plant cell wall has been described as providing strength and support to the cell. However, it has also been shown to play a role in maintaining cell function. Guard cells are ubiquitous structures found on the epidermis of the leaf surface, that function to regulate gas exchange, minimize water loss and block pathogen entry into internal spaces within the leaf. In arabidopsis, two members of the hydroxyproline-rich glycoprotein superfamily, ATPRP2 and ATPRP4 have been identified. The genes encoding these two proteins have been shown to be expressed in trichromes, lateral root primordia, and guard cells.
While the expression patterns are known, the localization and functional roles of these proteins remains unclear. DNA sequence analysis reveals that ATPRP2 and ATPRP4 are multi-domain proteins that are characterized by a Domain of Unknown function 1210 on the amino terminus of the protein and a proline-rich domain on the carboxyl tenninal end. Here I describe a function for the DUF1210 domain, providing evidence for its role in the targeted secretion of these proteins to the cuticle ledge and ventral wall of stomata. We identified evolutionarily distant homologs of the arabidopsis DUF1210 sequence and provide evidence that this domain is conserved in its function.
Using a reverse genetics approach, we provide evidence that ATPRP2 and ATPRP4 differentially influence the stomatal closure response to darkness and abscisic acid. Aberrant stomatal phenotypes in the atprp2 and atprp4 mutants indicate that ATPRP2 and ATPRP4 are necessary components of the plant cell wall and that they contribute to a cell wall structure that is critical for overall guard cell function and signaling. This work provides the first evidence for a role of structural cell wall proteins in determining stomatal function and increases our understanding of the importance of the plant extracellular matrix in cell signaling.
While the expression patterns are known, the localization and functional roles of these proteins remains unclear. DNA sequence analysis reveals that ATPRP2 and ATPRP4 are multi-domain proteins that are characterized by a Domain of Unknown function 1210 on the amino terminus of the protein and a proline-rich domain on the carboxyl tenninal end. Here I describe a function for the DUF1210 domain, providing evidence for its role in the targeted secretion of these proteins to the cuticle ledge and ventral wall of stomata. We identified evolutionarily distant homologs of the arabidopsis DUF1210 sequence and provide evidence that this domain is conserved in its function.
Using a reverse genetics approach, we provide evidence that ATPRP2 and ATPRP4 differentially influence the stomatal closure response to darkness and abscisic acid. Aberrant stomatal phenotypes in the atprp2 and atprp4 mutants indicate that ATPRP2 and ATPRP4 are necessary components of the plant cell wall and that they contribute to a cell wall structure that is critical for overall guard cell function and signaling. This work provides the first evidence for a role of structural cell wall proteins in determining stomatal function and increases our understanding of the importance of the plant extracellular matrix in cell signaling.