title: Plasma membrane-bound AGC3 kinases phosphorylate PIN auxin carriers at TPRXS(N/S) motifs to direct apical PIN recycling.
abstract: Polar membrane cargo delivery is crucial for establishing cell polarity and for directional transport processes. In plants, polar trafficking mediates the dynamic asymmetric distribution of PIN FORMED (PIN) carriers, which drive polar cell-to-cell transport of the hormone auxin, thereby generating auxin maxima and minima that control development. The Arabidopsis PINOID (PID) protein kinase instructs apical PIN localization by phosphorylating PINs. Here, we identified the PID homologs WAG1 and WAG2 as new PIN polarity regulators. We show that the AGC3 kinases PID, WAG1 and WAG2, and not other plant AGC kinases, instruct recruitment of PINs into the apical recycling pathway by phosphorylating the middle serine in three conserved TPRXS(N/S) motifs within the PIN central hydrophilic loop. Our results put forward a model by which apolarly localized PID, WAG1 and WAG2 phosphorylate PINs at the plasma membrane after default non-polar PIN secretion, and trigger endocytosis-dependent apical PIN recycling. This phosphorylation-triggered apical PIN recycling competes with ARF-GEF GNOM-dependent basal recycling to promote apical PIN localization. In planta, expression domains of PID, WAG1 and WAG2 correlate with apical localization of PINs in those cell types, indicating the importance of these kinases for apical PIN localization. Our data show that by directing polar PIN localization and PIN-mediated polar auxin transport, the three AGC3 kinases redundantly regulate cotyledon development, root meristem size and gravitropic response, indicating their involvement in both programmed and adaptive plant development.
authors.affiliation: Section of Molecular Genetics, Department of Biology, Utrecht University, Padualaan 8, Utrecht, The Netherlands. p.b.dhonukshe@uu.nl
authors.forename: Pankaj
authors.initials: P
authors.lastname: Dhonukshe
authors.forename: Fang
authors.initials: F
authors.lastname: Huang
authors.forename: Carlos S
authors.initials: CS
authors.lastname: Galvan-Ampudia
authors.forename: Ari Pekka
authors.initials: AP
authors.lastname: Mähönen
authors.forename: Jurgen
authors.initials: J
authors.lastname: Kleine-Vehn
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.forename: Ab
authors.initials: A
authors.lastname: Quint
authors.forename: Kalika
authors.initials: K
authors.lastname: Prasad
authors.forename: Jirí
authors.initials: J
authors.lastname: Friml
authors.forename: Ben
authors.initials: B
authors.lastname: Scheres
authors.forename: Remko
authors.initials: R
authors.lastname: Offringa
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004705:Endocytosis; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D010766:Phosphorylation; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; D017346:Protein Serine-Threonine Kinases; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C405165:PINOID protein, Arabidopsis; C552692:WAG1 protein, Arabidopsis; C542125:WAG2 protein, Arabidopsis