Transcriptional regulation of phosphate transporters from Lolium perenne and its mycorrhizal symbionts in response to phosphorus supply

Phosphate (P) uptake is critical for plant growth, but to date little is known about P uptake and transport in the pasture grass Lolium perenne L. We have identified a putative P transporter (PT) from L. perenne mycorrhizal roots (LpPT1) and assessed its transcriptional regulation by soil P availability and mycorrhizal colonisation. We also investigated transcript levels of fungal PTs from the two arbuscular mycorrhizal species Rhizophagus intraradices and Funneliformis mosseae. Our analyses indicated that LpPT1 codes for a high affinity PT most likely responsible for direct P uptake from the soil. LpPT1 is highly expressed in roots of plants grown at low P, whereas high P repressed its expression. LpPT1 was not expressed in above-ground plant tissues. Colonisation with R. intraradices did not affect expression of LpPT1 significantly. Transcript levels of the R. intraradices PT were not affected by P availability but the F. mosseae PT was repressed by high P supply, particularly in intraradical hyphae. Our study could assist in deciphering the molecular mechanisms of P uptake in the pasture grass L. perenne.