Molecular Genetic and Biochemical Analysis of the Fimbrin Gene Family From Arabidopsis

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The central importance of the actin cytoskeleton to plant development has been widely accepted for some years now; however, little detailed biochemical analysis of the individual components that regulate actin-based function has been performed. This project addresses this deficiency by characterizing at the biochemical, cellular and genetic levels, the family of fimbrin-like actin filament crosslinking proteins from Arabidopsis thaliana. A major component of this project will exploit reverse-genetic approaches by identifying knockout mutants for each of the five fimbrin sequences. Phenotypic analysis of these knockout lines will include determining whole plant defects and examining the detailed structure of the actin cytoskeleton in different cell types by using immunofluorescence and GFP technology. Specific actin-based functions such as chloroplast orientation, cytoplasmic streaming, determination of division planes, response to fungal pathogens, and cell expansion will be analyzed in the knockout lines. Collectively, this study will test the hypothesis that Arabidopsis contains members of the fimbrin family with distinct biochemical and cellular properties and which, therefore, have the potential to contribute to the diversity of actin-based function within individual plant cells. Furthermore, this potential for diverse functions will be tested directly by exploiting the power of reverse genetics. The results obtained will provide important insight into fundamental mechanisms that underpin cellular morphogenesis and responses to extracellular stimuli.