The high-affinity poplar ammonium importer PttAMT1.2 and its role in ectomycorrhizal symbiosis
Article first published online: 31 AUG 2005
Volume 168, Issue 3, pages 697–706, December 2005
How to Cite
Selle, A., Willmann, M., Grunze, N., Geßler, A., Weiß, M. and Nehls, U. (2005), The high-affinity poplar ammonium importer PttAMT1.2 and its role in ectomycorrhizal symbiosis. New Phytologist, 168: 697–706. doi: 10.1111/j.1469-8137.2005.01535.x
- Issue published online: 31 AUG 2005
- Article first published online: 31 AUG 2005
- Received: 29 April 2005 Accepted: 29 June 2005
- plant nitrogen (N) nutrition;
- • One way to elucidate whether ammonium could act as a nitrogen (N) source delivered by the fungus in ectomycorrhizal symbiosis is to investigate plant ammonium importers.
- • Expression analysis of a high-affinity ammonium importer from Populus tremula× tremuloides (PttAMT1.2) and of known members of the AMT1 gene family from Populus trichocarpa was performed. In addition, PttAMT1.2 function was studied in detail by heterologous expression in yeast.
- • PttAMT1.2 expression proved to be root-specific, affected by N nutrition, and strongly increased in a N-independent manner upon ectomycorrhiza formation. The corresponding protein had a KM value for ammonium of c. 52 µm. From the seven members of the AMT1 gene family, one gene was exclusively expressed in roots while four genes were detectable in all poplar organs but with varying degrees of expression. Ectomycorrhiza formation resulted in a strong upregulation of three of these genes.
- • Our results indicate an increased ammonium uptake capacity of mycorrhized poplar roots and suggest, together with the expression of putative ammonium exporter genes in the ectomycorrhizal fungus Amanita muscaria, that ammonium could be a major N source delivered from the fungus towards the plant in symbiosis.