Ayling S M, Smith S E, Smith F A
1 Department of Soil and Water, University of Adelaide, South Australia 5005, Australia.
New Phytol. 2000 Sep;147(3):631-639. doi: 10.1046/j.1469-8137.2000.00723.x.
Measurements of the electric potential difference across the hyphal wall and the cell membrane were made on external hyphae of three species of arbuscular mycorrhizal fungus Gigaspora margarita, Scutellospora calospora and Glomus coronatum and on germ tubes of Gi. margarita. The values of transmembrane electric potential difference recorded (∼-40 mV) are less negative than those previously reported from hyphae of arbuscular mycorrhizal fungi closely associated with roots and from filamentous fungi. The external hyphae of arbuscular mycorrhizal fungi grown in soil had similar values of electric potential difference to those grown in soil-less culture, and to germ tubes. Thermodynamic calculations showed that despite these low values of electric potential difference, efficient high-affinity uptake of phosphate is possible. The transmembrane electric potential difference of germ tubes of Gi. margarita became more negative when plant root extract was added to the medium, showing for the first time that the early stages of interaction between plant and fungus occur via direct effects on the plasma membrane rather than via effects on gene expression. Addition of K reversibly depolarized the transmembrane electric potential difference of germ tubes of Gi. margarita, indicating that despite the low electric potential difference the fungus has control over the permeability of the plasmamembrane to K .
对三种丛枝菌根真菌（珠状巨孢囊霉、美孢盾巨孢囊霉和冠球囊霉）的外部菌丝以及珠状巨孢囊霉的芽管进行了跨菌丝壁和细胞膜的电势差测量。所记录的跨膜电势差的值（约-40 mV）比先前报道的与根紧密相关的丛枝菌根真菌菌丝和丝状真菌的电势差负值要小。生长在土壤中的丛枝菌根真菌的外部菌丝与无土培养条件下生长的菌丝以及芽管具有相似的电势差值。热力学计算表明，尽管电势差值较低，但仍有可能实现高效的高亲和力磷酸盐吸收。当向培养基中添加植物根提取物时，珠状巨孢囊霉芽管的跨膜电势差变得更负，首次表明植物与真菌相互作用的早期阶段是通过对质膜的直接影响而非对基因表达的影响发生的。添加钾会使珠状巨孢囊霉芽管的跨膜电势差可逆地去极化，这表明尽管电势差较低，但真菌对质膜对钾的通透性具有控制作用。
