Analysis of protein structural elements, cations and sugars as modulators of osmotin's antifungal activity
Abstract
Antifungal activities of plant defense proteins are profoundly altered in the presence of sugars and inorganic cations such as calcium and potassium. Little is known at the molecular level of how these effects are mediated, but they have substantial biological implications for plant-pathogen interactions. These solute and cation effects are the subject of the present investigation. Sugars accumulating in ripening grapes were found to substantially increase activity of a coordinately accumulating antifungal chitinase and a PR5 protein against the important grape pathogens Guignardia bidwellii and Botrytis cinerea. This developmentally controlled response appears to constitute a novel defense mechanism developed in fruits. Biochemical and genetic analyses of the tobacco PR5 protein osmotin in a yeast-based system demonstrated that calcium materially increases the protein's antifungal activity by facilitating an extracellular interaction involving an acidic cleft region on the osmotin surface and phosphomannans on the yeast cell surface. Potassium also affects this interaction, but in the opposite manner, suppressing osmotin activity. Models of how these solute and ion effects occur are presented.
Degree
Ph.D.
Advisors
Bressan, Purdue University.
Subject Area
Molecular biology|Plant pathology|Biochemistry
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