The use of optical displacement microviscometry (ODM) and reconstituted model systems to measure aluminum-induced changes in the organization and viscosity of actin

Absorption of aluminum from acidic soils and surface waters can have significant adverse consequences for plant growth and development. Such deleterious effects range from stunted root growth to death. Despite the agricultural importance of the problem and years of intense study, investigations have yielded neither definitive targets nor unambiguous molecular mechanism(s) for aluminum toxicity in plant cells.;In pure actin solutions, the effects of aluminum were not apparent until after the addition of nonphysiologically high concentrations. However, inclusion of an actin binding protein that cross-links actin filaments, e.g., myosin or filamin, altered the organization of the actin solution in a way that decreased the concentration of aluminum (20 ;Recent findings in our laboratory suggest that aluminum may function as a cytoskeletal toxicant. Evidence has been presented that the actin filament network is a potential target for the adverse effects of aluminum in plant cells. Aluminum interaction with actin networks can modify the dynamic properties of these actin filaments sufficiently to result in the abnormal growth phenotypes observed for aluminum toxicity. This dissertation describes the development of a new assay, Optical Displacement Microviscometry (ODM), to measure the viscosity of actin solutions in a reconstituted model system. The experiments performed with this technique in a reconstituted system were designed to characterize the components of the actin network and their interactions that are potentially affected by the addition of aluminum. An attractive feature of the ODM technique is that it utilizes a laser optical trap to perform viscosity measurements in microvolumes of solution (...