title: A major facilitator superfamily transporter plays a dual role in polar auxin transport and drought stress tolerance in Arabidopsis.
abstract: Many key aspects of plant development are regulated by the polarized transport of the phytohormone auxin. Cellular auxin efflux, the rate-limiting step in this process, has been shown to rely on the coordinated action of PIN-formed (PIN) and B-type ATP binding cassette (ABCB) carriers. Here, we report that polar auxin transport in the Arabidopsis thaliana root also requires the action of a Major Facilitator Superfamily (MFS) transporter, Zinc-Induced Facilitator-Like 1 (ZIFL1). Sequencing, promoter-reporter, and fluorescent protein fusion experiments indicate that the full-length ZIFL1.1 protein and a truncated splice isoform, ZIFL1.3, localize to the tonoplast of root cells and the plasma membrane of leaf stomatal guard cells, respectively. Using reverse genetics, we show that the ZIFL1.1 transporter regulates various root auxin-related processes, while the ZIFL1.3 isoform mediates drought tolerance by regulating stomatal closure. Auxin transport and immunolocalization assays demonstrate that ZIFL1.1 indirectly modulates cellular auxin efflux during shootward auxin transport at the root tip, likely by regulating plasma membrane PIN2 abundance. Finally, heterologous expression in yeast revealed that ZIFL1.1 and ZIFL1.3 share H(+)-coupled K(+) transport activity. Thus, by determining the subcellular and tissue distribution of two isoforms, alternative splicing dictates a dual function for the ZIFL1 transporter. We propose that this MFS carrier regulates stomatal movements and polar auxin transport by modulating potassium and proton fluxes in Arabidopsis cells.
authors.affiliation: Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal.
authors.forename: Estelle
authors.initials: E
authors.lastname: Remy
authors.forename: Tânia R
authors.initials: TR
authors.lastname: Cabrito
authors.forename: Pawel
authors.initials: P
authors.lastname: Baster
authors.forename: Rita A
authors.initials: RA
authors.lastname: Batista
authors.forename: Miguel C
authors.initials: MC
authors.lastname: Teixeira
authors.forename: Jiri
authors.initials: J
authors.lastname: Friml
authors.forename: Isabel
authors.initials: I
authors.lastname: Sá-Correia
authors.forename: Paula
authors.initials: P
authors.lastname: Duque
mesh_terms: D000220:Adaptation, Biological; D017398:Alternative Splicing; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D018519:Meristem / Q000378:metabolism; D054046:Plant Stomata / Q000235:genetics / Q000378:metabolism; D018526:Plant Transpiration; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D059386:Reverse Genetics; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; C117013:AT5G57090 protein, Arabidopsis