The rate of P acquisition and translocation in extraradical hyphae of acid-tolerant arbuscular mycorrhizal fungi under low pH conditions

摘要

Arbuscular mycorrhizal (AM) fungi play a significant role in the survival and growth of pioneer plants in extreme environments. Recently, we isolated acid-tolerant AM fungi from acidic soil. The objective of present study was to evaluate the efficiency of P uptake and translocation of the fungi under acidic conditions with respect to polyphosphate (polyP) as a translocation form of P in the fungi. Lotus japonicus cv. Miyakojima was inoculated with Archaeospora leptoticha OK-15 MAEF520072 (from volcanic acid soil), Glomus sp. HR1 (from acid sulfate soil) or Glomus etunicatum MAFF520053 (from arable soil) and grown on 1:3 acid sulfate soil-river sand mixtures (pH 4.3 and 7.0) in a dual mesh bag system in which the hyphal compartment (HC) and the mycorrhizal (roots+hyphae) compartment (MC) were separated by a 10 mm P-diffusion barrier (P-deficient red soil) between 37 μm nylon mesh bags. After 7-weeks, 1 mM P solution was applied to the HC, and extraradical hyphae in both compartments were collected. PolyP content was determined by the polyP kinase-luciferase method. Only acid-tolerant fungi colonized and promoted the growth of the host. The rate of P uptake and subsequent polyP accumulation in the hyphae were very rapid in contrast to that of polyP translocation through the hyphae. Difference in the rate of P translocation among the isolates are discussed.