title: A petunia ABC protein controls strigolactone-dependent symbiotic signalling and branching.
abstract: Strigolactones were originally identified as stimulators of the germination of root-parasitic weeds that pose a serious threat to resource-limited agriculture. They are mostly exuded from roots and function as signalling compounds in the initiation of arbuscular mycorrhizae, which are plant-fungus symbionts with a global effect on carbon and phosphate cycling. Recently, strigolactones were established to be phytohormones that regulate plant shoot architecture by inhibiting the outgrowth of axillary buds. Despite their importance, it is not known how strigolactones are transported. ATP-binding cassette (ABC) transporters, however, are known to have functions in phytohormone translocation. Here we show that the Petunia hybrida ABC transporter PDR1 has a key role in regulating the development of arbuscular mycorrhizae and axillary branches, by functioning as a cellular strigolactone exporter. P. hybrida pdr1 mutants are defective in strigolactone exudation from their roots, resulting in reduced symbiotic interactions. Above ground, pdr1 mutants have an enhanced branching phenotype, which is indicative of impaired strigolactone allocation. Overexpression of Petunia axillaris PDR1 in Arabidopsis thaliana results in increased tolerance to high concentrations of a synthetic strigolactone, consistent with increased export of strigolactones from the roots. PDR1 is the first known component in strigolactone transport, providing new opportunities for investigating and manipulating strigolactone-dependent processes.
authors.affiliation: Institute of Plant Biology, University of Zurich, 8008 Zurich, Switzerland. t.kretzschmar@irri.org
authors.forename: Tobias
authors.initials: T
authors.lastname: Kretzschmar
authors.forename: Wouter
authors.initials: W
authors.lastname: Kohlen
authors.forename: Joelle
authors.initials: J
authors.lastname: Sasse
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Borghi
authors.forename: Markus
authors.initials: M
authors.lastname: Schlegel
authors.forename: Julien B
authors.initials: JB
authors.lastname: Bachelier
authors.forename: Didier
authors.initials: D
authors.lastname: Reinhardt
authors.forename: Ralph
authors.initials: R
authors.lastname: Bours
authors.forename: Harro J
authors.initials: HJ
authors.lastname: Bouwmeester
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000040:Abscisic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects* / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination; D007783:Lactones / Q000494:pharmacology*; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000187:drug effects; D009280:Naphthaleneacetic Acids / Q000494:pharmacology; D032306:Petunia / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010937:Plant Growth Regulators / Q000494:pharmacology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D015398:Signal Transduction / Q000187:drug effects*; D013559:Symbiosis / Q000187:drug effects*
chemical_list: D018528:ATP-Binding Cassette Transporters; C507382:GR24 compound; D007783:Lactones; D009280:Naphthaleneacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins; C472678:orobanchol; C034182:1-naphthaleneacetic acid; D000040:Abscisic Acid