Increased trehalose biosynthesis in Hartig net hyphae of ectomycorrhizas.
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.
López
Mónica Fajardo
MF
Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
Männer
Philipp
P
Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
Willmann
Anita
A
Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
Hampp
Rüdiger
R
Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
Nehls
Uwe
U
Eberhard Karls Universität, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
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
D014199:Trehalose; D005964:Glucosyltransferases; C023180:trehalose-6-phosphate synthase; C023181:alpha,alpha-trehalose phosphorylase; C023178:trehalose-phosphatase; D010744:Phosphoric Monoester Hydrolases; D009584:Nitrogen