Hoffmann E, Wallenda T, Schaeffer C, Hampp R
Universität Töbingen, Physiologische Okologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Töbingen, Germany.
New Phytol. 1997 Oct;137(2):351-356. doi: 10.1046/j.1469-8137.1997.00798.x.
The amounts of cyclic AMP (cAMP), fructose-2,6-bisphosphate (F26BP), trehalose and glycogen were determined in cell suspension cultures of the ectomycorrhiza-forming fungus Amanita muscaria (L. ex Fr.) Hooker. For the assay of cAMF a protocol was developed that enabled the detection of as little as 50 fmol of this secondary messenger by an enzyme-linked immuno assay (EIA). Values varied from < 1 and up to 5 pmol cAMP mg d. wt according to the age of the fungal culture. Typically, a transient increase in cAMP occurred after c. 4 d of culture of the fungus on glucose-containing medium. This increase (up to 100%) was followed by the start of the logarithmic growth phase, and by a more persistent increase in F26BP. In parallel, glucose in the medium started to decrease, whilst the amounts of fungal carbohydrates, especially the disaccharide trehalose, increased, From these data we assume that a high initial rate of glucose uptake caused an increase in the fungal pools of storage carbohydrates and, via activation of an adenylate cyclase, of cAMP. According to data reported for yeast cells this should enhance the formation of F26BP by phosphorylation of relevant enzymes. In animal and yeast cells an increase in the concentration of F26BP stimulates glycolysis by activation of the ATP-dependent phosphofructokinase (PFK). A. muscaria also possesses an F26BP activated PFK and, under conditions of symbiosis, host-derived carbohydrates are supplied mainly in the form of glucose. The implications of these findings to the regulation of carbohydrate metabolism of symbiotic plant root/fungus structures (ectomycorrhiza) are discussed.
测定了外生菌根形成真菌毒蝇鹅膏（Amanita muscaria (L. ex Fr.) Hooker）细胞悬浮培养物中环磷酸腺苷（cAMP）、果糖-2,6-二磷酸（F26BP）、海藻糖和糖原的含量。对于cAMP的测定，开发了一种方案，通过酶联免疫分析（EIA）能够检测低至50飞摩尔的这种第二信使。根据真菌培养物的年龄，cAMP的值在<1至5皮摩尔cAMP毫克干重之间变化。通常，在真菌在含葡萄糖培养基上培养约4天后，cAMP会出现短暂增加。这种增加（高达100%）之后是对数生长期的开始，以及F26BP更持续的增加。同时，培养基中的葡萄糖开始减少，而真菌碳水化合物的量，尤其是二糖海藻糖增加。从这些数据我们推测，高初始葡萄糖摄取率导致真菌储存碳水化合物池增加，并通过激活腺苷酸环化酶导致cAMP增加。根据酵母细胞的报道数据，这应该会通过相关酶的磷酸化增强F26BP的形成。在动物和酵母细胞中，F26BP浓度的增加通过激活ATP依赖性磷酸果糖激酶（PFK）刺激糖酵解。毒蝇鹅膏也拥有一种F26BP激活的PFK，并且在共生条件下，宿主衍生的碳水化合物主要以葡萄糖的形式供应。讨论了这些发现对共生植物根/真菌结构（外生菌根）碳水化合物代谢调节的影响。
