Molecular Genetic Analysis of Cell Polarity in the Maize Leaf Epidermis

University Of California-San Diego, La Jolla CA

Investigators

Abstract

0212724 Smith As in all other eukaryotes and prokaryotes, diversification of form and function during plant development depends on cell polarity. Relatively little is known in molecular terms about how cells translate polarizing cues into localized cytoskeletal assemblies that direct the polarization of other cell components or of the cell growth machinery. With the support of a prior NSF award, a genetic approach was taken to analyze mechanisms by which maize leaf epidermal cells become polarized, focusing on three Brick (Brk) genes required for the polarized growth and division of epidermal cells. Building on this work, studies are proposed here to further advance our understanding of plant cell polarity, with the following specific objectives: 1. Complementary approaches will be taken to localize BRK1 protein in polarizing subsidiary mother cells and expanding epidermal pavement cells. 2. Complementary approaches will be taken to identify candidate BRK1-interacting proteins and investigate their in vivo interactions with BRK1. 3. As shown for the Brk genes, two Pangloss (Pan) genes promote the polarization of subsidiary mother cells, but are not required for polarized cell expansion. The functions of Pan genes and how they relate to those of Brk genes will be further elucidated through phenotypic analysis of single and double mutants. 4. To help build a bigger picture of how maize leaf epidermal cells become polarized, one additional epidermal cell polarity gene (Pan1, Brk2, or Brk3) will be cloned and molecularly characterized by means of transposon tagging. The intellectual merit of the work proposed is augmented by the central importance of cell polarity in the development of all eukaryotes and prokaryotes, and the fact that BRK1 (and probably the entire pathway in which all 3 Brk genes were shown to function) is conserved among eukaryotes. Therefore, our findings will most likely have an impact outside the boundaries of plant cell biology. The broader impact of the work proposed will mainly be the education and training of young scientists participating in the research, including one postdoc, one Ph.D. student, and a series of undergraduates.