Two differentially regulated phosphate transporters from the symbiotic fungus Hebeloma cylindrosporum and phosphorus acquisition by ectomycorrhizal Pinus pinaster.
Ectomycorrhizal symbiosis markedly improves plant phosphate uptake, but the molecular mechanisms underlying this benefit are still poorly understood. We identified two ESTs in a cDNA library prepared from the ectomycorrhizal basidiomycete Hebeloma cylindrosporum with significant similarities to phosphate transporters from the endomycorrhizal fungus Glomus versiforme and from non-mycorrhizal fungi. The full-length cDNAs corresponding to these two ESTs complemented a yeast phosphate transport mutant (Deltapho84). Measurements of (33)P-phosphate influx into yeast expressing either cDNA demonstrated that the encoded proteins, named HcPT1 and HcPT2, were able to mediate Pi:H(+) symport with different affinities for Pi (K(m) values of 55 and 4 mum, respectively). Real-time RT-PCR showed that Pi starvation increased the levels of HcPT1 transcripts in H. cylindrosporum hyphae grown in pure culture. Transcript levels of HcPT2 were less dependent on Pi availability. The two transporters were expressed in H. cylindrosporum associated with its natural host plant, Pinus pinaster, grown under low or high P conditions. The presence of ectomycorrhizae increased net Pi uptake rates into intact Pinus pinaster roots at low or high soil P levels. The expression patterns of HcPT1 and HcPT2 indicate that the two fungal phosphate transporters may be involved in uptake of phosphate from the soil solution under the two soil P availability conditions used.
Tatry
Marie-Violaine
MV
UMR 1222 INRA/SupAgro, Biogéochimie du Sol et de la Rhizosphère, INRA, Centre de Montpellier, 2 place Viala, Montpellier Cedex 1, France.
El Kassis
Elie
E
Lambilliotte
Raphaël
R
Corratgé
Claire
C
van Aarle
Ingrid
I
Amenc
Laurie K
LK
Alary
Rémi
R
Zimmermann
Sabine
S
Sentenac
Hervé
H
Plassard
Claude
C
D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D020224:Expressed Sequence Tags; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D015723:Gene Library; D055364:Hebeloma / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000235:genetics / Q000378:metabolism; D028061:Phosphate Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D028223:Pinus / Q000378:metabolism* / Q000382:microbiology; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013559:Symbiosis
D018076:DNA, Complementary; D004271:DNA, Fungal; D005656:Fungal Proteins; D028061:Phosphate Transport Proteins; D010758:Phosphorus