Effects of aluminium on polyphosphate mobilization of the ectomycorrhizal fungus Suillus bovinus

Abstract

Aluminium toxicity may be an important factor in the decline in vitality of many forest trees and the associated ectomycorrhizal fungal flora. In this study, comparative in vivo 31P NMR investigations on Al-adapted and non-Aladapted fungus of Suillus bovinus in pure culture have produced interesting new data. With respect to intracellular compartments, 31P NMR spectroscopy showed the spectra to differ in a peak-6 ppm appearing in the spectra of the A1-adapted fungus indicating terminal phosphate groups of mobile polyphosphate. Thus, in the Al-adapted fungus the average chain length of mobile polyphosphate is considerably shorter than in the non-Al-adapted fungus. A special method of cyclic phosphate supply followed by block averaging of the NMR spectra was used to determine the kinetic behaviour of phosphate uptake, storage and incorporation into polyphosphate at a constant external pH 3.5. While the Al-adapted fungus showed resistance to Al, an irreversible break-down in phosphate metabolism of the non-Al-adapted fungus by exposure to Al was caused. In comparison with the non-Al-adapted fungus supplied by nutrient solutions omitting Al, the Al-adapted fungus showed higher levels in both phosphate uptake and mobile polyphosphate concentration. As a consequence of these results a de-toxification of freely mobile Al-ions into a stable and insoluble complex in the Al-adapted fungus is considered to be due to a capture of intracellular Al by mobile polyphosphate of shorter chain length.