title: Carbon allocation in ectomycorrhizas: identification and expression analysis of an Amanita muscaria monosaccharide transporter.
abstract: Ectomycorrhizas are formed between certain soil fungi and fine roots of predominantly woody plants. An important feature of this symbiosis is the supply of plant-derived carbohydrates to the fungus. As a first step toward a better understanding of the molecular basis of this process, we cloned a monosaccharide transporter from the ectomycorrhizal fungus Amanita muscaria. Degenerate oligonucleotide primers were designed to match conserved regions from known fungal sugar transporters. A cDNA fragment of the transporter was obtained from mycorrhizal mRNA by reverse transcription-polymerase chain reaction. This fragment was used to identify a clone (AmMst1) encoding the entire monosaccharide transporter in a Picea abies/A. muscaria mycorrhizal cDNA library. The cDNA codes for an open reading frame of 520 amino acids, showing best homology to a Neurospora crassa monosaccharide transporter. The function of AmMST1 as monosaccharide transporter was confirmed by heterologous expression of the cDNA in a Schizosaccharomyces pombe mutant lacking a monosaccharide uptake system. AmMst1 was constitutively expressed in fungal hyphae under all growth conditions. Nevertheless, in mycorrhizas as well as in hyphae grown at monosaccharide concentrations above 5 mM, the amount of AmMst1 transcript increased fourfold. We therefore suggest that AmMst1 is upregulated in ectomycorrhizas by a monosaccharide-controlled mechanism.
authors.affiliation: Universität Tübingen, Germany. uwe.nehls@uni-tuebingen.de
authors.forename: U
authors.initials: U
authors.lastname: Nehls
authors.forename: J
authors.initials: J
authors.lastname: Wiese
authors.forename: M
authors.initials: M
authors.lastname: Guttenberger
authors.forename: R
authors.initials: R
authors.lastname: Hampp
mesh_terms: D000545:Amanita / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D016384:Consensus Sequence; D017124:Conserved Sequence; D017931:DNA Primers; D005656:Fungal Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D015723:Gene Library; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D009492:Neurospora crassa / Q000235:genetics; D016366:Open Reading Frames; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis; D014197:Trees / Q000382:microbiology
chemical_list: D017931:DNA Primers; D005656:Fungal Proteins; C111094:MST-1 protein, Amanita muscaria; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins