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Characterization of a carbohydrate transporter from symbiotic glomeromycotan fungi


The symbiotic relationships between mycorrhizal fungi and plants have an enormous impact on terrestrial ecosystems1. Most common are the arbuscular mycorrhizas, formed by fungi belonging to the phylum Glomeromycota2. Arbuscular mycorrhizal fungi facilitate the uptake of soil nutrients by plants3 and in exchange obtain carbohydrates, thus representing a large sink4 for atmospheric plant-fixed CO2. However, how carbohydrates are transported through the symbiotic interface is still unknown. Here we report the characterization of the first known glomeromycotan monosaccharide transporter, GpMST1, by exploiting the unique symbiosis of a glomeromycotan fungus (Geosiphon pyriformis) with cyanobacteria5. The GpMST1 gene has a very low GC content and contains six introns with unusual boundaries. GpMST1 possesses twelve predicted transmembrane domains and functions as a proton co-transporter with highest affinity for glucose, then mannose, galactose and fructose. It belongs to an as yet uncharacterized phylogenetic monosaccharide transporter clade. This initial characterization of a new transporter family involved in fungal symbiosis will lead to a better understanding of carbon flows in terrestrial environments.

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Figure 1: Comparison of bidirectional phosphate and carbon exchanges.
Figure 2: The G. pyriformis MST1.
Figure 3: 14 C-glucose uptake in GpMST1-expressing yeast strain EBY.VW4000.


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We thank E. Boles (University of Frankfurt) for providing EBY.VW4000 and CEN.PK2-1C yeast strains, D. Rentsch (University of Bern) for providing pDR196, and J. Gossmann (University of Frankfurt) for proofreading. This work was supported by grants from the Deutsche Forschungsgemeinschaft to D.C., H.M. and A.S. Author Contributions A.S., H.M. and D.C. isolated the full-length GpMST1 cDNA clones and performed semiquantitative RT–PCR. A.S. and D.C. retransformed EBY.VW4000, and performed screenings and growth tests. H.M. modified the pDR196 vector, constructed the cDNA libraries, and performed initial yeast transformations and screenings. M.F. performed the uptake assays. D.C. helped with uptake assays and performed gDNA amplification, PCR and clonings. A.S. made the phylogenetic analyses; A.S. and D.W. are responsible for the experimental design, hypotheses, interpreting the results and writing the manuscript.

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Correspondence to Arthur Schüßler.

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Sequences are deposited at EMBL Data Bank with the accession numbers AM231332 (GpMST1 cDNA clone pHM13-C6.1) and AM231333 (GpMST1 gDNA clone pDC-C6). Plasmids and clones are available on request. Reprints and permissions information is available at The authors declare no competing financial interests.

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Supplementary Information

This file contains Supplementary Figures 1-3. Supplementary Figures 1 and 2 show phylogenetic analyses revealing the affiliation of GpMST1 to a clade containing sequences of yet uncharacterized putative fungal transporters. In Supplementary Figure 3, the intron-exon boundaries of GpMST1 are shown in comparison to consensus sequences from other organisms. (PDF 177 kb)

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Schüßler, A., Martin, H., Cohen, D. et al. Characterization of a carbohydrate transporter from symbiotic glomeromycotan fungi. Nature 444, 933–936 (2006).

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