Demonstration of a short chain polyphosphate in Pisolithus tinctorius and the implications for phosphorus transport

Abstract

SUMMARYPolyphosphate was extracted from an Australian isolate oi Pisolithus tinctorius (Pers.) Coker & Couch, known to he mycorrhizal with Eucalyptus pilularis. It was separated from RNA and characterized hy PAGE and ^^F NMR spectroscopy. A broad pink hand, which showed y-metachromasy with toiuidine blue, ran faster on acrylamide gels than a number of purple-blue bands (various RNA fractions) and did not stain with ethidium bromide, was identified as polyphosphate. The major pink band co-migraied with a synthetic polyphosphate standard of a chain length of about 1 5 phosphate (PJ subunits, and analysis by ^^P nuclear magnetic resonance (NMR) spectroscopy confirmed that polyphosphate was a major fraction in the extract. Polyphosphate was extracted from mycelium grown at both high and low levels of P,, but the amount extracted from cultures grown with 10 mM P, (added as ammonium phosphate) was significantly greater, Polyphosphate was a substantial fraction of the phosphorus present in the hyphae and it is proposed that polyphosphate is transported along the hyphae by the motile tubule and vacuole system present in this fungus.

A 31P nuclear magnetic resonance study of phosphate levels in roots of ectomycorrhizal and nonmycorrhizal plants of Castanea sativa Mill.

“…Polyphosphates occur in a wide range of fungi as well as in the fungal component of all types of mycorrhizal associations examined so far (Chilvers et al 1985;MacFall et al 1992;Ashford et al 1994). It has been suggested that it plays a role in plant nutrition by allowing rapid accumulation of phosphate in an inactive form when phosphate is abundant (Harley and Smith 1983;Ashford et al 1994).…”

“…It has been suggested that it plays a role in plant nutrition by allowing rapid accumulation of phosphate in an inactive form when phosphate is abundant (Harley and Smith 1983;Ashford et al 1994). In mycorrhiza, the uptake of P seems to be first as a Pi pool, followed by accumulation as polyphosphates (Grellier et al 1989;MacFall et al 1992).…”

“…In mycorrhiza, the uptake of P seems to be first as a Pi pool, followed by accumulation as polyphosphates (Grellier et al 1989;MacFall et al 1992). When phosphate level is low, it is slowly transferred to the partner (Harley and Smith 1983;MacFall et al 1992;Ashford et al 1994). This is a selective advantage in conditions where phosphate availability fluctuates.…”

“…Currently there is a great interest in understanding the role of the extramatrical mycelium in phosphate uptake and transfer to the symbiont interface (Ashford et al 1994). It was suggested that phosphate is translocated along hyphae as polyphosphate granules inside vacuoles (Cox et al 1980).…”

“…However, this contention has been challenged, and these granules are most likely artifacts (Ashford et al 1994, Smith andRead 1997). Ectomycorrhizal hyphae actively growing in axenic culture are thought to accumulate phosphate mainly as orthophosphate, in contrast to the fungal mantle and ectomycorrhizal fungi during stationary phase, which store it as polyphosphates (Martin et al 1985;Ashford et al 1994). Metachromatic vacuolar material can easily be observed in several strains of P. tinctorius when actively growing in liquid medium or on agar (Ashford et al 1994).…”