Mansouri-Bauly Hounayda, Kruse Jörg, Sýkorová Zuzana, Scheerer Ursula, Kopriva Stanislav
Albert-Ludwigs-University of Freiburg, Institute of Forest Botany and Tree Physiology, Georges-Köhler-Allee 053, 79110, Freiburg, Germany.
The School of Forest and Ecosystem Science, University of Melbourne, Melbourne, Australia.
Mycorrhiza. 2006 Sep;16(6):421-427. doi: 10.1007/s00572-006-0052-y. Epub 2006 Apr 5.
The importance of the ectomycorrhiza symbiosis for plant acquisition of phosphorus and nitrogen is well established whereas its contribution to sulfur nutrition is only marginally understood. In a first step to investigate the role of ectomycorrhiza in plant sulfur nutrition, we characterized sulfate and glutathione uptake in Laccaria bicolor. By studying the regulation of sulfate uptake in this ectomycorrhizal fungus, we found that in contrast to bacteria, yeast, and plants, sulfate uptake in L. bicolor was not feedback-inhibited by glutathione. On the other hand, sulfate uptake was increased by sulfur starvation as in other organisms. The activity of 3'-phosphoadenosine 5'-phosphosulfate reductase, the key enzyme of the assimilatory sulfate reduction pathway in fungi, was increased by sulfur starvation and decreased after treatment with glutathione revealing an uncoupling of sulfate uptake and reduction in the presence of reduced sulfur compounds. These results support the hypothesis that L. bicolor increases sulfate supply to the plant by extended sulfate uptake and the plant provides the ectomycorrhizal fungus with reduced sulfur.
外生菌根共生对于植物获取磷和氮的重要性已得到充分证实，而其对硫营养的贡献却鲜为人知。作为研究外生菌根在植物硫营养中作用的第一步，我们对双色蜡蘑中硫酸盐和谷胱甘肽的吸收进行了表征。通过研究这种外生菌根真菌中硫酸盐吸收的调控，我们发现与细菌、酵母和植物不同，双色蜡蘑中的硫酸盐吸收不受谷胱甘肽的反馈抑制。另一方面，与其他生物一样，硫饥饿会增加硫酸盐的吸收。真菌同化硫酸盐还原途径的关键酶3'-磷酸腺苷5'-磷酸硫酸还原酶的活性在硫饥饿时增加，在用谷胱甘肽处理后降低，这表明在存在还原态硫化合物的情况下，硫酸盐的吸收和还原发生了解偶联。这些结果支持了这样的假设，即双色蜡蘑通过扩大硫酸盐吸收来增加向植物的硫酸盐供应，而植物则为外生菌根真菌提供还原态硫。
