title: The E3 ubiquitin ligase SCFTIR1/AFB and membrane sterols play key roles in auxin regulation of endocytosis, recycling, and plasma membrane accumulation of the auxin efflux transporter PIN2 in Arabidopsis thaliana.
abstract: The PIN family of auxin efflux transporters exhibit polar plasma membrane (PM) localization and play a key role in auxin gradient-mediated developmental processes. Auxin inhibits PIN2 endocytosis and promotes its PM localization. However, the underlying mechanisms remain elusive. Here, we show that the inhibitory effect of auxin on PIN2 endocytosis was impaired in SCF(TIR1/AFB) auxin signaling mutants. Similarly, reducing membrane sterols impaired auxin inhibition of PIN2 endocytosis. Gas chromatography-mass spectrometry analyses indicate that membrane sterols were significantly reduced in SCF(TIR1/AFB) mutants, supporting a link between membrane sterols and auxin signaling in regulating PIN2 endocytosis. We show that auxin promoted PIN2 recycling from endosomes to the PM and increased PIN2 steady state levels in the PM fraction. Furthermore, we show that the positive effect of auxin on PIN2 levels in the PM was impaired by inhibiting membrane sterols or auxin signaling. Consistent with this, the sterol biosynthetic mutant fk-J79 exhibited pronounced defects in primary root elongation and gravitropic response. Our data collectively indicate that, although there are distinct processes involved in endocytic regulation of specific PM-resident proteins, the SCF(TIR1/AFB)-dependent processes are required for auxin regulation of endocytosis, recycling, and PM accumulation of the auxin efflux transporter PIN2 in Arabidopsis thaliana.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401, USA.
authors.forename: Jianwei
authors.initials: J
authors.lastname: Pan
authors.forename: Shozo
authors.initials: S
authors.lastname: Fujioka
authors.forename: Jianling
authors.initials: J
authors.lastname: Peng
authors.forename: Jianghua
authors.initials: J
authors.lastname: Chen
authors.forename: Guangming
authors.initials: G
authors.lastname: Li
authors.forename: Rujin
authors.initials: R
authors.lastname: Chen
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004705:Endocytosis / Q000235:genetics / Q000502:physiology*; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008401:Gas Chromatography-Mass Spectrometry; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018522:Gravitropism / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000032:analysis; D007210:Indoleacetic Acids / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018517:Plant Roots / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000032:analysis; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics; D013261:Sterols / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D044783:F-Box Proteins; D006023:Glycoproteins; D049452:Green Fluorescent Proteins; D007210:Indoleacetic Acids; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D044843:SKP Cullin F-Box Protein Ligases; D013261:Sterols; C117013:AT5G57090 protein, Arabidopsis; C501405:TIR1 protein, Arabidopsis