title: Interactions among PIN-FORMED and P-glycoprotein auxin transporters in Arabidopsis.
abstract: Directional transport of the phytohormone auxin is established primarily at the point of cellular efflux and is required for the establishment and maintenance of plant polarity. Studies in whole plants and heterologous systems indicate that PIN-FORMED (PIN) and P-glycoprotein (PGP) transport proteins mediate the cellular efflux of natural and synthetic auxins. However, aromatic anion transport resulting from PGP and PIN expression in nonplant systems was also found to lack the high level of substrate specificity seen in planta. Furthermore, previous reports that PGP19 stabilizes PIN1 on the plasma membrane suggested that PIN-PGP interactions might regulate polar auxin efflux. Here, we show that PGP1 and PGP19 colocalized with PIN1 in the shoot apex in Arabidopsis thaliana and with PIN1 and PIN2 in root tissues. Specific PGP-PIN interactions were seen in yeast two-hybrid and coimmunoprecipitation assays. PIN-PGP interactions appeared to enhance transport activity and, to a greater extent, substrate/inhibitor specificities when coexpressed in heterologous systems. By contrast, no interactions between PGPs and the AUXIN1 influx carrier were observed. Phenotypes of pin and pgp mutants suggest discrete functional roles in auxin transport, but pin pgp mutants exhibited phenotypes that are both additive and synergistic. These results suggest that PINs and PGPs characterize coordinated, independent auxin transport mechanisms but also function interactively in a tissue-specific manner.
authors.affiliation: Department of Horticulture, Purdue University, West Lafayette, Indiana 47907-2010, USA.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Blakeslee
authors.forename: Anindita
authors.initials: A
authors.lastname: Bandyopadhyay
authors.forename: Ok Ran
authors.initials: OR
authors.lastname: Lee
authors.forename: Jozef
authors.initials: J
authors.lastname: Mravec
authors.forename: Boosaree
authors.initials: B
authors.lastname: Titapiwatanakun
authors.forename: Michael
authors.initials: M
authors.lastname: Sauer
authors.forename: Srinivas N
authors.initials: SN
authors.lastname: Makam
authors.forename: Yan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Bouchard
authors.forename: Jirí
authors.initials: J
authors.lastname: Adamec
authors.forename: Markus
authors.initials: M
authors.lastname: Geisler
authors.forename: Akitomo
authors.initials: A
authors.lastname: Nagashima
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sakai
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.forename: Jirí
authors.initials: J
authors.lastname: Friml
authors.forename: Wendy Ann
authors.initials: WA
authors.lastname: Peer
authors.forename: Angus S
authors.initials: AS
authors.lastname: Murphy
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001692:Biological Transport / Q000502:physiology; D018546:Hypocotyl / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; C114215:ATPGP1 protein, Arabidopsis; C519873:PGP19 protein, Arabidopsis; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C510494:Pgp4 protein, Arabidopsis