title: Functional PTB phosphate transporters are present in streptophyte algae and early diverging land plants.
abstract: Two inorganic phosphate (Pi) uptake mechanisms operate in streptophytes and chlorophytes, the two lineages of green plants. PHOSPHATE TRANSPORTER B (PTB) proteins are hypothesized to be the Na+/Pi symporters catalysing Pi uptake in chlorophytes, whereas PHOSPHATE TRANSPORTER 1 (PHT1) proteins are the H+/Pi symporters that carry out Pi uptake in angiosperms. PHT1 proteins are present in all streptophyte lineages. However, Pi uptake in streptophyte algae and marine angiosperms requires Na+influx, suggesting that Na+/Pi symporters also function in some streptophytes. We tested the hypothesis that Na+/Pi symporters exist in streptophytes. We identified PTB sequences in streptophyte genomes. Core PTB proteins are present at the plasma membrane of the liverwort Marchantia polymorpha. The expression of M. polymorpha core PTB proteins in the Saccharomyces cerevisiae pho2 mutant defective in high-affinity Pi transport rescues growth in low-Pi environments. Moreover, levels of core PTB mRNAs of M. polymorpha and the streptophyte alga Coleochaete nitellarum are higher in low-Pi than in Pi-replete conditions, consistent with a role in Pi uptake from the environment. We conclude that land plants inherited two Pi uptake mechanisms - mediated by the PTB and PHT1 proteins, respectively - from their streptophyte algal ancestor. Both systems operate in parallel in extant early diverging land plants.
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Clémence
authors.initials: C
authors.lastname: Bonnot
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Hélène
authors.initials: H
authors.lastname: Proust
authors.affiliation: Centre National de la Recherche Scientifique (CNRS), UMR 5095 Institut de Biochimie et Génétique Cellulaire (IBGC), Bordeaux Cedex, F-33077, France.|Université de Bordeaux, Bordeaux, F-33000, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Pinson
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Florine P L
authors.initials: FP
authors.lastname: Colbalchini
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Alexis
authors.initials: A
authors.lastname: Lesly-Veillard
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Holger
authors.initials: H
authors.lastname: Breuninger
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Clément
authors.initials: C
authors.lastname: Champion
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Hetherington
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Steven
authors.initials: S
authors.lastname: Kelly
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
authors.forename: Liam
authors.initials: L
authors.lastname: Dolan
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000460:Chlorophyta / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D019669:Embryophyta / Q000187:drug effects / Q000378:metabolism*; D005816:Genetic Complementation Test; D057927:Hydrophobic and Hydrophilic Interactions; D047008:Marchantia / Q000187:drug effects / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D028061:Phosphate Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism
chemical_list: D028061:Phosphate Transport Proteins; D010710:Phosphates; D012333:RNA, Messenger
keywords: 
  Coleochaete nitellarum
  ; 
  Marchantia polymorpha
  ; PTB Pi transporters; Pi uptake; early diverging land plants; streptophyte algae