Arabidopsis thaliana provides a model system in which both molecular genetic and cell biology approaches can be used to evaluate and define the function of structural proteins in the plant cell wall. Proline rich proteins (PRPs) represent afamily of structural cell wall proteins which have been implicated as contributing to maintenance of cell function and in generalized defense mechanisms in response to plant stress. Transgenic plants expressing a tagged version of a PRP will be used to 1) explore the pattern of cell wall deposition for this protein during plant development; and 2) to examine the ability of this protein to become crosslinked within walls of different cell types. Mutants altered in the development of cell types associated with the expression of this protein will also be characterized to determine if changes in cell shape and function observed in these mutants can disrupt or alter normal PRP/wall interactions. Using a similar approach, several other members of the Arabidopsis PRP(AtPRP) gene family will be analyzed to determine if individual gene family members make unique contributions to extracellular matrix structure in specific cell types. A PCR-based screen to identify potential T-DNA insertion mutants for several members of the AtPRP gene family will be initiated. Mutants identified from these screens will be characterized at a molecular level and, if time permits, will be analyzed for phenotypes associated with the loss of AtPRP expression.