title: The ABC transporter AtABCB14 is a malate importer and modulates stomatal response to CO2.
abstract: Carbon dioxide uptake and water vapour release in plants occur through stomata, which are formed by guard cells. These cells respond to light intensity, CO2 and water availability, and plant hormones. The predicted increase in the atmospheric concentration of CO2 is expected to have a profound effect on our ecosystem. However, many aspects of CO2-dependent stomatal movements are still not understood. Here we show that the ABC transporter AtABCB14 modulates stomatal closure on transition to elevated CO2. Stomatal closure induced by high CO2 levels was accelerated in plants lacking AtABCB14. Apoplastic malate has been suggested to be one of the factors mediating the stomatal response to CO2 (Refs 4,5) and indeed, exogenously applied malate induced a similar AtABCB14-dependent response as high CO2 levels. In isolated epidermal strips that contained only guard cells, malate-dependent stomatal closure was faster in plants lacking the AtABCB14 and slower in AtABCB14-overexpressing plants, than in wild-type plants, indicating that AtABCB14 catalyses the transport of malate from the apoplast into guard cells. Indeed, when AtABCB14 was heterologously expressed in Escherichia coli and HeLa cells, increases in malate transport activity were observed. We therefore suggest that AtABCB14 modulates stomatal movement by transporting malate from the apoplast into guard cells, thereby increasing their osmotic pressure.
authors.affiliation: Postech-UZH Global Research Laboratory, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Miyoung
authors.initials: M
authors.lastname: Lee
authors.forename: Yongwook
authors.initials: Y
authors.lastname: Choi
authors.forename: Bo
authors.initials: B
authors.lastname: Burla
authors.forename: Yu-Young
authors.initials: YY
authors.lastname: Kim
authors.forename: Byeongwook
authors.initials: B
authors.lastname: Jeon
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Maeshima
authors.forename: Joo-Yeon
authors.initials: JY
authors.lastname: Yoo
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.forename: Youngsook
authors.initials: Y
authors.lastname: Lee
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D035264:Flowers / Q000187:drug effects / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D008293:Malates / Q000378:metabolism* / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D054046:Plant Stomata / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D013997:Time Factors
chemical_list: C532485:ABCB14 protein, Arabidopsis; D018435:ATP Binding Cassette Transporter, Subfamily B; D029681:Arabidopsis Proteins; D008293:Malates; D002245:Carbon Dioxide; C030298:malic acid