Mechanisms of Plant Cell Morphogenesis: ARP2/3 Function and Trichome Distortion in Arabidopsis

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Intellectual Merit of the Proposed ActivitiesThe long-term goal of Dr. Szymanski's research program is to use Arabidopsis morphology mutants and all available experimental tools to understand the basic mechanisms of cell shape control. The primary objective of this proposal is to determine if an actin filament-nucleating machine, termed the ARP2/3 complex, exists in plants, and if so, its function during polarized growth. The central hypothesis of this proposal is that an Arabidopsis ARP2/3 complex modulates actin filament nucleation and vacuole biogenesis during epidermal development. His group plans to test our central hypothesis by pursuing the following three specific aims.Specific Aim #1: To determine if the distorted trichome phenotype is caused exclusively by mutation of ARP2/3 subunit genes.Specific Aim #2: To test for the existence and essential function of a seven protein Arabidopsis ARP2/3 complex.Dr. Szymanski's use of forward molecular genetics, novel live cell imaging assays, and biochemical tools is an innovative approach to study ARP2/3 function in a multicellular organism. Upon completion of the proposed work his group expects to determine if a plant ARP2/3 complex is essential. He expects to establish functional relationships between ARP2/3 subunit localization, the organization of the actin cytoskeleton, and specific organelle trafficking steps in the cell. These data will provide new knowledge about how complex organisms utilize ARP2/3 subunits to control cell shape and tissue function. Dr. Szymanski is extremely well qualified to undertake the proposed research. He has the most extensive set of ARP2/3 subunit mutants, and has generated an extensive collection of DNA and protein-based reagents that will permit functional analyses. Broader impacts of the proposed research The integration of research and learning activities in the Szymanski laboratory ensures that his program has a broad impact on society. Dr. Szymanski published two book chapters and two teaching-oriented reviews on plant morphogenesis. This grant requests continued funding for undergraduate, graduate, and post-doctoral fellow research opportunities. Part of the research experience for graduate and post-graduate students will include lab and classroom teaching opportunities. Some of the undergraduate student support will be used to teach engineering and computer science students image processing and mutant phenotype quantitation. Dr. Szymanski actively participates in the MARC-AIM and a departmental graduate student recruiting program, both of which focus on increasing minority student participation in science. Dr. Szymanski will make the materials developed in this proposal available to the scientific community, and some of them will be used in college and high school genetics laboratory exercises. Last, Dr. Szymanski, as a Co.P.I. on instrumentation grants, has improved the infrastructure and use of fluorescence microscopy for many biologists at Purdue University. Collectively, the efforts described in this proposal are aimed at translating basic research activities into broad-based educational experiences that promote the excitement and relevance of the scientific process.