Abstract
BackgroundIn plants, the uptake from soil and intercellular transport of inorganic phosphate (Pi) is mediated by the PHT1 family of membrane-spanning proton : Pi symporters. The Arabidopsis thaliana AtPHT1 gene family comprises nine putative high-affinity Pi transporters. While AtPHT1;1 to AtPHT1;4 are involved in Pi acquisition from the rhizosphere, the role of the remaining transporters is less clear.ResultsPi uptake and tissue accumulation studies in AtPHT1;8 and AtPHT1;9 knock-out mutants compared to wild-type plants showed that both transporters are involved in the translocation of Pi from the root to the shoot. Upon inactivation of AtPHT1;9, changes in the transcript profiles of several genes that respond to plant phosphorus (P) status indicated a possible role in the regulation of systemic signaling of P status within the plant. Potential genetic interactions were found among PHT1 transporters, as the transcript profile of AtPHT1;5 and AtPHT1;7 was altered in the absence of AtPHT1;8, and the transcript profile of AtPHT1;7 was altered in the Atpht1;9 mutant. These results indicate that AtPHT1;8 and AtPHT1;9 translocate Pi from the root to the shoot, but not from the soil solution into the root.ConclusionAtPHT1;8 and AtPHT1;9 are likely to act sequentially in the interior of the plant during the root-to-shoot translocation of Pi, and play a more complex role in the acclimation of A. thaliana to changes in Pi supply than was previously thought.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0334-z) contains supplementary material, which is available to authorized users.
Highlights
In plants, the uptake from soil and intercellular transport of inorganic phosphate (Pi) is mediated by the PHT1 family of membrane-spanning proton : Inorganic phosphate (Pi) symporters
Transcripts from individual AtPHT1 genes responded differentially to Pi deprivation and re-supply The remodeling kinetics of the AtPHT1 transcript pool in response to both P depletion and Pi re-supply were examined in well-established Arabidopsis plants prior to inflorescence emergence. In this and the following experiments, whenever Pi was supplied, the supply was set to be sufficient for non-limited growth, without being luxuriant
Plants were transferred to nutrient solution containing either no added Pi (P-deprived) or added Pi (Pi re-supply)
Summary
The uptake from soil and intercellular transport of inorganic phosphate (Pi) is mediated by the PHT1 family of membrane-spanning proton : Pi symporters. Plants acquire P from the soil in its most oxidized inorganic form, phosphate (Pi) [1]. The uptake of Pi into the plant occurs against a steep electrochemical gradient. Pi uptake from the soil and transport within the plant against this concentration gradient is mediated by Pi transporters. The first eukaryotic Pi transporter protein to be described was the PHO84p H+ : Pi symporter in yeast [4], followed by plant homologs [5,6]. From the numerous plant sequences available, four PHOSPHATE TRANSPORTER (PHT) families are recognised: PHT1 (plasma membrane), PHT2 (plastid inner envelope), PHT3 (mitochondrial inner membrane) and PHT4 (mostly plastid envelope and one Golgi-localized transporter) [7,8]
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