Max Planck Institute of Molecular Plant Physiology, Am Muehlenberg 1, 14476, Potsdam, Germany.
New Phytol. 2013 Jan;197(2):606-616. doi: 10.1111/nph.12034. Epub 2012 Nov 28.
Arbuscular mycorrhizal (AM) symbiosis is a mutualistic interaction that occurs between the large majority of vascular plants and fungi of the phylum Glomeromycota. In addition to other nutrients, sulfur compounds are symbiotically transferred from AM fungus to host plants; however, the physiological importance of mycorrhizal-mediated sulfur for plant metabolism has not yet been determined. We applied different sulfur and phosphate fertilization treatments to Medicago truncatula and investigated whether mycorrhizal colonization influences leaf metabolite composition and the expression of sulfur starvation-related genes. The expression pattern of sulfur starvation-related genes indicated reduced sulfur starvation responses in mycorrhizal plants grown at 1 mM phosphate nutrition. Leaf metabolite concentrations clearly showed that phosphate stress has a greater impact than sulfur stress on plant metabolism, with no demand for sulfur at strong phosphate starvation. However, when phosphate nutrition is high enough, mycorrhizal colonization reduces sulfur stress responses, probably as a result of symbiotic sulfur uptake. Mycorrhizal colonization is able to reduce sulfur starvation responses in M. truncatula when the plant's phosphate status is high enough that sulfur starvation is of physiological importance. This clearly shows the impact of mycorrhizal sulfur transfer on plant metabolism.
丛枝菌根（AM）共生是一种发生在大多数维管植物和球囊霉门真菌之间的互利共生关系。除了其他养分外，硫化合物也从 AM 真菌共生体中被协同转运到宿主植物中；然而，丛枝菌根介导的硫对植物代谢的生理重要性尚未确定。我们应用不同的硫和磷酸盐施肥处理方法，研究了丛枝菌根定殖是否会影响叶片代谢物组成和与硫饥饿相关基因的表达。与硫饥饿相关基因的表达模式表明，在 1 mM 磷酸盐营养条件下生长的丛枝菌根植物的硫饥饿反应减少。叶片代谢物浓度清楚地表明，磷酸盐胁迫对植物代谢的影响大于硫胁迫，在强烈的磷酸盐饥饿下，植物不需要硫。然而，当磷酸盐营养足够高时，丛枝菌根定殖会降低硫胁迫反应，这可能是由于共生体吸收硫的结果。当植物的磷酸盐状况足够高，以至于硫饥饿对植物的生理状况变得重要时，丛枝菌根定殖能够降低 M. truncatula 中的硫饥饿反应。这清楚地表明了丛枝菌根转移硫对植物代谢的影响。
