Normal development is characterized by the formation of cells, tissues, and organs in appropriate places and patterns. A major challenge in the field of developmental biology is to understand how distinct cell types arise in appropriate patterns. This project will address this issue by using root epidermis development in Arabidopsis as a simple model. In prior work, a new receptor (named SCRAMBLED (SCM)) was found to play a critical role in enabling developing epidermal cells to interpret their position relative to the underlying root cells. A working model was proposed whereby the SCM receptor influences a network of transcriptional regulators in a position-dependent manner to generate the observed cell-type pattern in the root epidermis. In this research project, this model will be tested by analyzing the accumulation and the specific function of the SCM receptor using molecular and genetic methods. In addition, new genes that are likely to act in a SCM-related manner will be identified in a genetic screen and in a differential expression-based microarray screen. The research results are expected to provide exciting new insights into the molecular regulation of cell specification and pattern formation during the development of multicellular organisms. Further, this project will have a broader impact in several areas. It will provide educational opportunities for undergraduates, graduate students, and postdoctoral students in modern biological research. The project will also provide information and educational material to the Arabidopsis research community and the general public, via a website (www.mcdb.lsa.umich.edu/labs/schiefel/index.html). Furthermore, the results will be incorporated into formal educational activities, including a new undergraduate developmental biology course and an interdisciplinary training program for undergraduates in biological and mathematical sciences, which immerses students in laboratory and theoretical research.
The formation of a living thing is dependent upon proper communication between its component cells and tissues, to ensure that the development of different parts of the organism occurs in an orderly and coordinated manner. A current challenge in the field of developmental biology is to define the specific signaling molecules and receptor molecules that are used for this communication and to understand how they function. The ultimate goal is to use this information to enable rational manipulation of developmental processes to generate plants and animals that will more efficiently provide the food, fiber, and fuel needed for the world’s growing population. In this project, we studied the molecules that control the formation of root hair cells in the reference plant Arabidopsis, as a simple experimental system to understand cell communication during development. We accomplished four major goals. First, we showed that the expression of the receptor gene in this system (called SCM) is controlled by a regulatory feedback loop, providing an explanation for how this gene is expressed in certain cells and not in others (see accompanying figure). Second, we misexpressed the SCM gene in specific ways and discovered that the regulatory feedback loop is necessary for the receptor to carry out its developmental function. Third, we identified new genes that influence this developmental signaling process, including a gene encoding a ribosome biogenesis factor, which suggests an unexpected connection between cellular communication and the machinery that makes proteins. Fourth, we discovered a molecule that is likely to interact with the receptor, which may serve to determine when and how the receptor is able to act. Altogether, this study provides new insights into the way receptors are used in cell communication to define the types and arrangements of cells. This project also generated broader impacts by providing a rich interdisciplinary training experience for undergraduates, graduate students, and postdoctoral fellows, including direct mentoring and educational activities in the biological and mathematical sciences. Further, it directly contributed to a new undergraduate training program in math biology, which was designed to cross disciplinary boundaries and to focus on training students from historically underrepresented groups. A new undergraduate course in developmental biology, emphasizing critical thinking and the conceptual similarities in developmental strategies in plants and animals, was also established as a part of this project.
