CAREER: Analysis of Signalling in Arabidopsis Carpel Patterning

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The goal of this research is to understand the signaling networks that regulate pattern in the Arabidopsis fruit. Classical experiments indicated a key role for intercellular signaling events during the development of the fruit in plants, but the signals and receptors involved have thus far not been identified. The aims of this proposal are to understand how fruit size and pattern are regulated in Arabidopsis. Using a screen of insertion mutants in Arabidopsis, mutants have been identified in four receptor kinase genes that share a common phenotype of extra organs in the fruit. The analysis of the phenotypes of the null alleles of these genes suggests these receptor kinases are critically important for establishing the developmental axes of the fruit. Because of the observed, shared phenotypes among the receptor mutants, a search was initiated for available mutations in potential ligands which revealed that brassinosteroids may play a role in cell signaling in the fruit primordia. The preliminary data suggests a lateral inhibition model of cell signaling in the floral meristem that produces the fruit. The specific aims of this proposal are: (1) to identify more components of this signaling network using genetic screens, (2) to determine if the receptor kinases are involved in lateral signaling through analysis of their expression patterns and characterization of the mutant phenotypes at the cellular level, and (3) to test the role of brassinosteroids in fruit patterning by using biochemical intermediates, mutants that are blocked at individual steps and an inhibitor of brassinosteroid biosynthesis.In the instructional portion of this project, several molecular-biology computer-lab modules will be developed. These are designed to accompany a lecture course for undergraduates in molecular biology, and one module will later be modified for public school outreach. The goals of these modules will be to teach basic concepts in molecular biology and to increase awareness of how biological technology affects our daily lives. One module will compare the traditional plant breeding approach with transgenic approaches, including both experimental methods and analysis of the economic and biological implications of developing crops. This module will teach students about the biology underlying the food they consume and prepare them for their future in both personal and political decision-making.Intellectual merit: The results of the proposed experiments will tell us how fruit size and pattern are regulated in Arabidopsis, and can be applied to understanding the regulation of fruit size in other plants. In domesticated crop plants, changes in the homologs of some of these genes may be responsible for the diversity in fruit size and morphology. This concept of the interplay between classical plant breeding, molecular genetics and the development of transgenic plants forms the basis of the educational part of the proposal.Broader impacts of this work: The proposed research, testing a model for signaling events that regulate patterning in Arabidopsis fruit, is interdisciplinary, combining genomics, genetics, molecular biology, and development. The experiments will provide training opportunities for undergraduates, graduate students and postdoctorals. The experiments also form the basis of some of the ideas for developing computer modules to accompany a molecular-biology lecture class. One of these modules will be redesigned with the input of teachers to be included in an ongoing outreach program to teach high-school students about plant-breeding strategies and genetically modified organisms. All modules developed for courses will be made available on the Internet for students and teachers. Both the Tucson public school and University of Arizona student populations provide opportunities to reach students from underrepresented groups.