Intellectual Merit: The plant cell wall is dynamic and can be modified in response to developmental and environmental signals. In this manner, the cell wall provides structural information that helps maintain cellular form and function during plant growth. Expression of many of the structural proteins in the wall have been shown to be cell-type specific, suggesting that these proteins may play novel roles in modifying cell wall structure in order to provide mechanical strength and assist in proper wall assembly.
Proline-rich proteins (PRPs) represent an integral family of structural cell wall proteins whose expression has been linked to active growth in a number of plant systems. Two of these proteins, AtPRP1 and AtPRP3, are expressed during the early stages of root hair outgrowth in Arabidopsis but are localized within different regions of the root hair cell wall. These results suggest that individual PRP gene family members may play distinct roles in helping to establish root hair cell wall structure during wall assembly. In addition, two other members of this gene family, AtPRP2 and AtPRP4, are expressed in guard cells and localize to the inner shelf and the wall surrounding the air space, respectively, of the guard cell wall. These studies will characterize the loss-of-function phenotypes in mutants associated with root hair and guard cell function. In addition, the investigator will examine the function of epitope-tagged PRP sequences in wildtype and mutant PRP backgrounds. In combination, these experimental approaches should provide new insight into the function of these proteins, the nature of the amino acid sequences encoded within individual AtPRPs that are sufficient for their targeted localization within the cell wall, and their insolubilization within the extracellular matrix.
Broader Impacts: Structural cell wall proteins have been implicated in maintaining cell shape and function during plant development. However, the mechanism(s) through which these proteins participate in modeling the structure of plant extracellular matrices in unique ways within different cell types is poorly understood. Results from the proposed research will provide new understanding of the primary sequences required for proline-rich protein function within the cell wall as well as cellular mechanisms responsible for the targeted secretion of PRPs to the growing walls of guard cells and root hairs in Arabidopsis. Long-term, this information may allow investigators to tailor plant extracellular matrix structure to support cell function of plants grown under adverse environmental conditions.
Funds provided by this proposal will also be used to support undergraduate and graduate student participation. Students involved in this research will report their experimental findings at national and international meetings.
