title: Expression and substrate specificity of betaine/proline transporters suggest a novel choline transport mechanism in sugar beet.
abstract: Proline transporters (ProTs) originally described as highly selective transporters for proline, have been shown to also transport glycinebetaine (betaine). Here we examined and compared the transport properties of Bet/ProTs from betaine accumulating (sugar beet, Amaranthus, and Atriplex,) and non-accumulating (Arabidopsis) plants. Using a yeast mutant deficient for uptake of proline and betaine, it was shown that all these transporters exhibited higher affinity for betaine than proline. The uptake of betaine and proline was pH-dependent and inhibited by the proton uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP). We also investigated choline transport by using a choline transport-deficient yeast mutant. Results revealed that these transporters exhibited a higher affinity for choline uptake rather than betaine. Uptake of choline by sugar beet BvBet/ProT1 was independent of the proton gradient and the inhibition by CCCP was reduced compared with that for uptake of betaine, suggesting different proton binding properties between the transport of choline and betaine. Additionally, in situ hybridization experiments revealed the localization of sugar beet BvBet/ProT1 in phloem and xylem parenchyma cells.
authors.affiliation: Graduate School of Environmental and Human Sciences, Meijo University, Nagoya 468-8502, Japan.
authors.forename: Nana
authors.initials: N
authors.lastname: Yamada
authors.forename: Shota
authors.initials: S
authors.lastname: Sakakibara
authors.forename: Koichi
authors.initials: K
authors.lastname: Tsutsumi
authors.forename: Rungaroon
authors.initials: R
authors.lastname: Waditee
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Teruhiro
authors.initials: T
authors.lastname: Takabe
mesh_terms: D027721:Amaranthus / Q000235:genetics / Q000378:metabolism; D026921:Amino Acid Transport Systems, Neutral / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D027466:Atriplex / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D027461:Beta vulgaris / Q000235:genetics / Q000378:metabolism*; D001622:Betaine / Q000378:metabolism*; D001692:Biological Transport; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002794:Choline / Q000378:metabolism*; D050485:GABA Plasma Membrane Transport Proteins; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009154:Mutation; D052585:Phloem / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011392:Proline / Q000378:metabolism*; D061209:Proton Ionophores / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D052584:Xylem / Q000378:metabolism
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; D010940:Plant Proteins; D061209:Proton Ionophores; C072207:betaine plasma membrane transport proteins; D001622:Betaine; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; C033082:proline transporter; D011392:Proline; D002794:Choline