CEPCEB Members

Eugene A. Nothnagel Professor of Plant Physiology and Plant Physiologist (Ph.D., Cornell University, 1981) Department of Botany and Plant Sciences Room 3202 Batchlor Hall University of California Riverside, CA 92521 Phone (951) 827-3777 FAX (951) 827-4437 Areas of Expertise Arabinogalactan Proteins Cell Wall Structure Plasma Membrane Structure and Dynamics
Background Research Interests Current Laboratory Personnel and Projects Selected Publications in Plant Cell Biology (Bibliography page)

Background

My formal training is principally in the physical sciences. As an undergraduate at the University of Minnesota, Morris, I completed Bachelor degrees in physics and mathematics and also completed a training program in secondary education in 1973. By that time my interests had focused on biophysics, which I pursued as a graduate student in physics at Southern Illinois University, Carbondale. Within my first year of graduate study, my interest in biophysics further sharpened to plant biophysics. Upon completion of a M.A. degree in physics, I moved to Cornell University where, in 1981, I completed a Ph.D. in applied physics with a minor in plant physiology. My Ph.D. dissertation, completed under the direction of Watt Webb, focused on the cytoskeletal basis and biophysical mechanism of cytoplasmic streaming in the giant alga Chara australis. I then undertook postgraduate research on oligosaccharide elicitors of soybean pathogen response at the University of Colorado, Boulder, under the direction of Peter Albersheim. In 1983, I came to my present position at the University of California, Riverside. My principal research emphasis at UCR was initially the biophysical properties of the plant plasma membrane and has gradually shifted to focus on one particular class of plasma membrane components, the arabinogalactan-proteins.

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Research Interests

Our research focuses on the structure and functions of arabinogalactan-proteins (AGPs), proteoglycans that are present on the plasma membrane and in the cell wall of all plants. Depending upon the cell type, we find that the response of live cells to perturbation of AGPs can lead to reversible inhibition of cell division, inhibition of cell expansion, or induction of programmed cell death. Some aspects of these responses to perturbed AGP function are similar to responses to wounding or pathogen attack, implying roles of AGPs in these processes. We have recently shown that some AGPs are anchored to the plasma membrane through a glycosylphosphatidylinositol lipid that is cleaved by a phospholipase to release the AGP into the cell wall. This finding is important for understanding the biological functions of AGPs in plant cells as well as for understanding the basis of their industrial applications as emulsifiers, a second project in our laboratory. Gum arabic, a mixture containing primarily AGPs, is an important flavor emulsifier used in certain soft drinks and other food products. We are investigating whether gum arabic AGPs contain glycosylphosphatidylinositol lipids that confer the emulsifier property.

Hypothetical structural model of an arabinogalactan-protein (AGP) carrying a glycosylphosphatidylinositol (GPI) lipid anchor. The ellipse represents the 15 nm by 25 nm size of a carrot AGP. The wavy line along the long axis of the ellipse represents the core polypeptide. The GPI anchor is similarly drawn to approximate scale. The site of cleavage by phosphatidylinositol-specific phospholipase C (PI-PLC) is indicated. Fluorescence (A) and brightfield (B) micrographs of suspension-cultured Arabidopsis cells at 12 hours of exposure to 50 µM (ß-D-Glc)3 Yariv phenylglycoside, a synthetic ligand that binds and aggregates AGPs. This perturabation of AGPs induces formation of papillae-like deposits of matrix material between the plasma membrane and the cell wall. These papillae like structures contain both callose, as indicated by fluorescence staining in A, and AGPs, as indicated by dark staining in B. Prolonged exposure to (ß-D-Glc)3 induces programmed cell death.

specific phospholipase C (PI-PLC) is indicated.

Current Laboratory Personnel and Projects

• Hu Fu, Graduate Student (Ph.D.). Structure of AGPs from Physcomitrella.

Selected Publications in Plant Cell Biology (Bibliography page)

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