title: SCF(TIR1/AFB)-auxin signalling regulates PIN vacuolar trafficking and auxin fluxes during root gravitropism.
abstract: The distribution of the phytohormone auxin regulates many aspects of plant development including growth response to gravity. Gravitropic root curvature involves coordinated and asymmetric cell elongation between the lower and upper side of the root, mediated by differential cellular auxin levels. The asymmetry in the auxin distribution is established and maintained by a spatio-temporal regulation of the PIN-FORMED (PIN) auxin transporter activity. We provide novel insights into the complex regulation of PIN abundance and activity during root gravitropism. We show that PIN2 turnover is differentially regulated on the upper and lower side of gravistimulated roots by distinct but partially overlapping auxin feedback mechanisms. In addition to regulating transcription and clathrin-mediated internalization, auxin also controls PIN abundance at the plasma membrane by promoting their vacuolar targeting and degradation. This effect of elevated auxin levels requires the activity of SKP-Cullin-F-box(TIR1/AFB) (SCF(TIR1/AFB))-dependent pathway. Importantly, also suboptimal auxin levels mediate PIN degradation utilizing the same signalling pathway. These feedback mechanisms are functionally important during gravitropic response and ensure fine-tuning of auxin fluxes for maintaining as well as terminating asymmetric growth.
authors.affiliation: Department of Plant Systems Biology, VIB and Department of Plant Biotechnology and Genetics, Ghent University, Gent, Belgium.
authors.forename: Paweł
authors.initials: P
authors.lastname: Baster
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Robert
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kleine-Vehn
authors.forename: Steffen
authors.initials: S
authors.lastname: Vanneste
authors.forename: Urszula
authors.initials: U
authors.lastname: Kania
authors.forename: Wim
authors.initials: W
authors.lastname: Grunewald
authors.forename: Bert
authors.initials: B
authors.lastname: De Rybel
authors.forename: Tom
authors.initials: T
authors.lastname: Beeckman
authors.forename: Jiří
authors.initials: J
authors.lastname: Friml
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D018522:Gravitropism / Q000235:genetics*; D007210:Indoleacetic Acids / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D044783:F-Box Proteins; D007210:Indoleacetic Acids; D011956:Receptors, Cell Surface; D044843:SKP Cullin F-Box Protein Ligases; C559638:AFB4 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C501405:TIR1 protein, Arabidopsis