Tatsuhiro Ezawa, Sally E Smith, F Andrew Smith
Departments of Soil and Water.
Environmental Biology, Centre for Plant Root Symbioses, The University of Adelaide, SA 5005 Australia.
New Phytol. 2001 Mar;149(3):555-563. doi: 10.1046/j.1469-8137.2001.00040.x.
• Regulation of polyphosphate metabolism is reported in arbuscular mycorrhizal symbiosis. • Marigold (Tagetes patula) plants inoculated with Glomus coronatum or Glomus etunicatum were grown in mesh bags. Exopolyphosphatase activity in extra- and intraradical hyphae was measured and characterized. The hyphae were stained with Neutral red to show acidic vacuoles in which polyphosphate synthesis might occur. • Exopolyphosphate activity was differently expressed between the extra- and intraradical hyphae, as indicated by different pH optima; high activity was observed at pH 5.0 in the intraradical hyphae of both fungal species. K values were lower at neutral pH with long-chain polyphosphate, whereas acidic activity showed lower K with short-chain polyphosphate. Both extra- and intradical hyphae had acidic vacuoles. Polyphosphate occurred in the hyphae of the high-P, but not the low-P treatment. By contrast, exopolyphosphatase activity and vacuolar acidity were relatively constant irrespective of polyphosphate status. • The fungi have at least two different exopolyphosphatase-type enzymes which are differently expressed between extra- and intraradical hyphae; polyphosphate accumulation might be a dynamic balance between synthesis and hydrolysis.
• 丛枝菌根共生中存在多聚磷酸盐代谢的调控。
• 用冠球囊霉或缩球囊霉接种的万寿菊（孔雀草）植株种植于网袋中。测定并表征了根外和根内菌丝体中的胞外磷酸酶活性。用中性红对菌丝进行染色，以显示可能发生多聚磷酸盐合成的酸性液泡。
• 根外和根内菌丝体中胞外磷酸酶活性的表达不同，这由不同的最适pH值表明；在两种真菌的根内菌丝体中，pH 5.0时观察到高活性。对于长链多聚磷酸盐，中性pH下的K值较低，而酸性活性下短链多聚磷酸盐的K值较低。根外和根内菌丝体均有酸性液泡。多聚磷酸盐存在于高磷处理的菌丝中，而低磷处理的菌丝中没有。相比之下，无论多聚磷酸盐状态如何，胞外磷酸酶活性和液泡酸度相对恒定。
• 真菌至少有两种不同类型的胞外磷酸酶，它们在根外和根内菌丝体中的表达不同；多聚磷酸盐的积累可能是合成与水解之间的动态平衡。
