title: Characterization of AgMaT2, a plasma membrane mannitol transporter from celery, expressed in phloem cells, including phloem parenchyma cells.
abstract: A second mannitol transporter, AgMaT2, was identified in celery (Apium graveolens L. var. dulce), a species that synthesizes and transports mannitol. This transporter was successfully expressed in two different heterologous expression systems: baker's yeast (Saccharomyces cerevisiae) cells and tobacco (Nicotiana tabacum) plants (a non-mannitol-producing species). Data indicated that AgMaT2 works as an H(+)/mannitol cotransporter with a weak selectivity toward other polyol molecules. When expressed in tobacco, AgMaT2 decreased the sensitivity to the mannitol-secreting pathogenic fungi Alternaria longipes, suggesting a role for polyol transporters in defense mechanisms. In celery, in situ hybridization showed that AgMaT2 was expressed in the phloem of leaflets, petioles from young and mature leaves, floral stems, and roots. In the phloem of petioles and leaflets, AgMaT2, as localized with specific antibodies, was present in the plasma membrane of three ontologically related cell types: sieve elements, companion cells, and phloem parenchyma cells. These new data are discussed in relation to the physiological role of AgMaT2 in regulating mannitol fluxes in celery petioles.
authors.affiliation: Unité Mixte de Recherche, Centre National de la Recherche Scientifique, 6161 Transport des Assimilats, Université de Poitiers, Bâtiment Botanique, 86022 Poitiers cedex, France.
authors.forename: Marjorie
authors.initials: M
authors.lastname: Juchaux-Cachau
authors.forename: Lucie
authors.initials: L
authors.lastname: Landouar-Arsivaud
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pichaut
authors.forename: Claire
authors.initials: C
authors.lastname: Campion
authors.forename: Benoit
authors.initials: B
authors.lastname: Porcheron
authors.forename: Julien
authors.initials: J
authors.lastname: Jeauffre
authors.forename: Nathalie
authors.initials: N
authors.lastname: Noiraud-Romy
authors.forename: Philippe
authors.initials: P
authors.lastname: Simoneau
authors.forename: Laurence
authors.initials: L
authors.lastname: Maurousset
authors.forename: Rémi
authors.initials: R
authors.lastname: Lemoine
mesh_terms: D000528:Alternaria / Q000502:physiology; D000077102:Apium / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D015870:Gene Expression; D008353:Mannitol / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D052585:Phloem / Q000166:cytology / Q000378:metabolism*; D010935:Plant Diseases; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000378:metabolism / Q000382:microbiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000382:microbiology
chemical_list: D026901:Membrane Transport Proteins; D010940:Plant Proteins; D008353:Mannitol