title: Increased trehalose biosynthesis in Hartig net hyphae of ectomycorrhizas.
abstract: To obtain photoassimilates in ectomycorrhizal symbiosis, the fungus has to create a strong sink, for example, by conversion of plant-derived hexoses into fungus-specific compounds. Trehalose is present in large quantities in Amanita muscaria and may thus constitute an important carbon sink. In Amanita muscaria-poplar (Populus tremula x tremuloides) ectomycorrhizas, the transcript abundances of genes encoding key enzymes of fungal trehalose biosynthesis, namely trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP) and trehalose phosphorylase (TP), were increased. When mycorrhizas were separated into mantle and Hartig net, TPS, TPP and TP expression was specifically enhanced in Hartig net hyphae. Compared with the extraradical mycelium, TPS and TPP expression was only slightly increased in the fungal sheath, while the increase in the expression of TP was more pronounced. TPS enzyme activity was also elevated in Hartig net hyphae, displaying a direct correlation between transcript abundance and turnover rate. In accordance with enhanced gene expression and TPS activity, trehalose content was 2.7 times higher in the Hartig net. The enhanced trehalose biosynthesis at the plant-fungus interface indicates that trehalose is a relevant carbohydrate sink in symbiosis. As sugar and nitrogen supply affected gene expression only slightly, the strongly increased expression of the investigated genes in mycorrhizas is presumably developmentally regulated.
authors: Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
authors: Mónica Fajardo
authors: MF
authors: López
authors: Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
authors: Philipp
authors: P
authors: Männer
authors: Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
authors: Anita
authors: A
authors: Willmann
authors: Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
authors: Rüdiger
authors: R
authors: Hampp
authors: Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
authors: Uwe
authors: U
authors: Nehls
mesh_terms: D000545:Amanita / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D050260:Carbohydrate Metabolism; D015870:Gene Expression; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D025301:Hyphae / Q000201:enzymology / Q000378:metabolism*; D038821:Mycorrhizae / Q000201:enzymology / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000382:microbiology* / Q000502:physiology; D017422:Sequence Analysis, DNA; D013559:Symbiosis / Q000502:physiology; D014199:Trehalose / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D014199:Trehalose; D005964:Glucosyltransferases; C023180:trehalose-6-phosphate synthase; C023181:alpha,alpha-trehalose phosphorylase; C023178:trehalose-phosphatase; D010744:Phosphoric Monoester Hydrolases; D009584:Nitrogen