PLASMA-MEMBRANE H-ATPASE ACTIVITY IN SPORES, GERM TUBES, AND HAUSTORIA OF THE RUST FUNGUS UROMYCES-VICIAE-FABAE()

Using plasma membrane-enriched vesicles, the properties of the H+-ATPa se (EC 3.6.1.35) from the rust fungus Uromyces viciae-fabae were studi ed. The enzyme is strictly Mg2+-dependent and is inhibited by vanadate , The pH-optimum is at 6.7. By Western blot analysis using a monoclona l antibody against corn plasma membrane H+-ATPase a polypeptide of app roximately 104 kDa could be detected. The vanadate-sensitive H+-ATPase activity of microsomal vesicles obtained from different stages of rus t development was determined, Uredospores had only a very low enzyme a ctivity (1.9 mu mol Pi x mg(-1) protein x h(-1)), In germ tubes the AT Pase activity was about twofold higher (4.0 mu mol Pi x mg(-1) protein x h(-1)). An eightfold higher ATPase activity (16.1 mu mol Pi x mg(-1 ) protein x h(-1)) was found in microsomal vesicles from haustoria whi ch had been isolated from rust-infected Vicia faba leaves, These resul ts suggest, that the electrochemical gradient generated by the H+-ATPa se of haustoria plays an important role for their function, possibly b y promoting nutrient uptake from host cells. (C) 1996 Academic Press, Inc.