Plant Biology

Mary L. Tierney

Associate Professor of Plant Biology

Ph.D. 1983, Michigan State University

Email: Mary.Tierney@uvm.edu

Phone: 802-656-0434

Office: 313 Jeffords Hall

Research Area: cell wall structure, signaling pathways, control of gene expression

Courses Taught: Ethics in Graduate Research (PBIO 295); Introduction to Botany (PBIO 004); Genetics (BCOR 101); Cell & Molecular Biology (CMB 302); Graduate Seminar (MMG 310)

AtPRP3 expression in root hairs

Summary of Research Program

The dynamic character of the cell wall provides a mechanism(s) by which plants selectively modify their extracellular matrix as a consequence of growth and differentiation. My research group is interested in understanding the mechanisms through which structural proteins within the plant cell wall determining aspects of cell form and function during plant development.

ATPRP3 localization in root hairs

We are currently studying a family of proline-rich cell wall proteins in Arabidopsis (AtPRPs) whose function is involved in tailoring the structure of the plant cell wall in root hairs and stomata. We have used promoter/reporter gene fusions in transgenic plants to show that the expression of individual AtPRPs is limited to these cell types and is linked to factors that control cell growth.

Wild type root hairs	atprp3-1 mutant root hairs

Studies in my lab have shown that each of the four ATPRPs is targeted to a specific region of the extracellular matrix, using immunohistochemistry. We have also identified knock-out mutants for each of these proteins. Null mutants for the two proteins expressed in root hairs (ATPRP1 and ATPRP3) present distinct root hair and whole plant phenotypes, suggesting that these proteins may serve different functions in organizing the structure of the primary cell wall. Future studies will focus on identifying changes in gene expression between wild type and mutant plants that would explain the developmental phenotypes observed in these mutants.

Stomata	ATPRP4 localization in stomata	ATPRP2 localization in stomata

We have also identified regions within each of the AtPRPs that are sufficient for their targeted secretion to unique regions within root hair and guard cell walls. In the future, we are interested in identifying components of the secretory pathway that are responsible for these targeting mechanisms and which provide a mechanism for selectively tailoring domains of the extracellular matrix to support cell function.

Selected Publications

• Hu, J., and M. L. Tierney. AtPRP3 protein localizes to the cell wall of the growing tip of root hairs in Arabidopsis. In preparation.
• Bernhardt, C. and M. L. Tierney.(2006) Proline-rich cell wall proteins: building blocks for an expanding cell wall? In T. Hayashi (Ed.), The science and lore of the plant cell wall: Biosynthesis, structure and function. Brown Walker Press, Boca Raton, Fl., pp. 164-170.
• Carpita, N., M. L. Tierney, and M. Campbell. (2001) Molecular biology of the plant cell wall: searching for the genes that define structure, architecture and dynamics. Plant Mol Biol. 47:1-5.
• Bernhardt, C. and M. L. Tierney. (2000) Expression of AtPRP3, a proline-rich structural cell wall protein from Arabidopsis, is regulated by cell-type-specific developmental pathways involved in root hair formation. Plant Physiol. 122(3):705-714.
• Fowler, T.J., C. Bernhardt, and M. L. Tierney. (1999) Characterization and expression of four proline-rich cell wall protein genes in Arabidopsis encoding two distinct subsets of multiple domain proteins. Plant Physiol. 121(4):1081-1092.