title: The vacuolar channel VvALMT9 mediates malate and tartrate accumulation in berries of Vitis vinifera.
abstract: Vitis vinifera L. represents an economically important fruit species. Grape and wine flavour is made from a complex set of compounds. The acidity of berries is a major parameter in determining grape berry quality for wine making and fruit consumption. Despite the importance of malic and tartaric acid (TA) storage and transport for grape berry acidity, no vacuolar transporter for malate or tartrate has been identified so far. Some members of the aluminium-activated malate transporter (ALMT) anion channel family from Arabidopsis thaliana have been shown to be involved in mediating malate fluxes across the tonoplast. Therefore, we hypothesised that a homologue of these channels could have a similar role in V. vinifera grape berries. We identified homologues of the Arabidopsis vacuolar anion channel AtALMT9 through a TBLASTX search on the V. vinifera genome database. We cloned the closest homologue of AtALMT9 from grape berry cDNA and designated it VvALMT9. The expression profile revealed that VvALMT9 is constitutively expressed in berry mesocarp tissue and that its transcription level increases during fruit maturation. Moreover, we found that VvALMT9 is targeted to the vacuolar membrane. Using patch-clamp analysis, we could show that, besides malate, VvALMT9 mediates tartrate currents which are higher than in its Arabidopsis homologue. In summary, in the present study we provide evidence that VvALMT9 is a vacuolar malate channel expressed in grape berries. Interestingly, in V. vinifera, a tartrate-producing plant, the permeability of the channel is apparently adjusted to TA.
authors: Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, Zurich, Switzerland. alexis.deangeli@botinst.uzh.ch
authors: Alexis
authors: A
authors: De Angeli
authors: Ulrike
authors: U
authors: Baetz
authors: Rita
authors: R
authors: Francisco
authors: Jingbo
authors: J
authors: Zhang
authors: Maria Manuela
authors: MM
authors: Chaves
authors: Ana
authors: A
authors: Regalado
mesh_terms: D001692:Biological Transport; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005638:Fruit / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D008293:Malates / Q000378:metabolism*; D027361:Organic Anion Transporters / Q000235:genetics* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011523:Protoplasts; D011993:Recombinant Fusion Proteins; D013644:Tartrates / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism; D027843:Vitis / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D008293:Malates; D027361:Organic Anion Transporters; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D013644:Tartrates; C030298:malic acid; C029768:tartaric acid
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