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Physiology and Biochemistry

Inhibition of Plasma Membrane and Tonoplast H⁺-Transporting ATPases by Glyceollin. John L. Giannini, Department of Agronomy and Plant Pathology, University of Illinois, Urbana 61801; Donald P. Briskin, Jana S. Holt, and Jack D. Paxton. Departments of Agronomy and Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 78:1000-1003. Accepted for publication 11 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1000.

The soybean phytoalexin glyceollin inhibits ATP-dependent proton transport associated with plasma membrane and tonoplast vesicles isolated from red beet (Beta vulgaris L.) storage tissue. Inhibition of proton transport by glyceollin in these vesicles was concentration dependent, and proton transport associated with tonoplast vesicles was more sensitive to the phytoalexin (50% inhibition at 50 µM) than that associated with plasma membrane vesicles (50% inhibition at 80 µM). When glyceollin was added to plasma membrane or tonoplast vesicles which developed a steady-state pH gradient, proton influx ceased; however, the gradient slowly dissipated. Glyceollin directly inhibited plasma membrane and tonoplast ATPase activity. The tonoplast ATPase was more sensitive to this compound than the plasma membrane ATPase. These results suggest that glyceollin could act to disrupt solute transport at both of these membranes through direct effects on the proton-pumping ATPases.