Intellectual merit. The plant hormone auxin plays a vital role in virtually every aspect of plant biology, from the organization of the plant embryo and the development of root and shoot system architecture to the control of growth in response to environmental cues. All of these processes depend on the formation of auxin gradients through local accumulation of auxin in plant cells and tissues. Increased auxin levels then activate different cellular responses in different cell types to coordinate plant growth. To understand how such local accumulation is achieved and which mechanisms determine the cellular specificity of auxin responses is the goal of this research program. It has recently been discovered that auxin elevation in root cells rapidly triggers an increase in cytosolic Ca2+ levels that can be visualized using live cell imaging approaches. Based on this discovery, this project will develop imaging assays to generate high-resolution maps of dynamic auxin signaling processes at the level of individual cells in real time. Such maps can provide quantitative empirical data delineating auxin transport routes, which can be used to strengthen and test current computational models of auxin-regulated plant development. This project further aims to develop genetic tools to control cytoplasmic Ca2+ levels and thereby to manipulate auxin signaling in a non-invasive, temporally and spatially controlled manner. This will help to define how Ca2+ contributes to the cellular specificity of auxin signaling.
Broader impacts. The project will provide training opportunities in modern molecular and cell biology techniques for one postdoctoral researcher and one graduate student. In addition, high school students participating in the Upward Bound Math and Science Summer Research Experience at Penn State will contribute to the project through an independent research project. In this project, the students will become acquainted with the basics of fluorescence microcopy and will generate transgenic Arabidopsis lines that will serve as useful tools for the plant scientific community.