title: D6PK AGCVIII kinases are required for auxin transport and phototropic hypocotyl bending in Arabidopsis.
abstract: Phototropic hypocotyl bending in response to blue light excitation is an important adaptive process that helps plants to optimize their exposure to light. In Arabidopsis thaliana, phototropic hypocotyl bending is initiated by the blue light receptors and protein kinases phototropin1 (phot1) and phot2. Phototropic responses also require auxin transport and were shown to be partially compromised in mutants of the PIN-FORMED (PIN) auxin efflux facilitators. We previously described the D6 PROTEIN KINASE (D6PK) subfamily of AGCVIII kinases, which we proposed to directly regulate PIN-mediated auxin transport. Here, we show that phototropic hypocotyl bending is strongly dependent on the activity of D6PKs and the PIN proteins PIN3, PIN4, and PIN7. While early blue light and phot-dependent signaling events are not affected by the loss of D6PKs, we detect a gradual loss of PIN3 phosphorylation in d6pk mutants of increasing complexity that is most severe in the d6pk d6pkl1 d6pkl2 d6pkl3 quadruple mutant. This is accompanied by a reduction of basipetal auxin transport in the hypocotyls of d6pk as well as in pin mutants. Based on our data, we propose that D6PK-dependent PIN regulation promotes auxin transport and that auxin transport in the hypocotyl is a prerequisite for phot1-dependent hypocotyl bending.
authors.affiliation: Department of Plant Systems Biology, Technische Universität München, 85354 Freising-Weihenstephan, Germany.
authors.forename: Björn C
authors.initials: BC
authors.lastname: Willige
authors.forename: Siv
authors.initials: S
authors.lastname: Ahlers
authors.forename: Melina
authors.initials: M
authors.lastname: Zourelidou
authors.forename: Inês C R
authors.initials: IC
authors.lastname: Barbosa
authors.forename: Emilie
authors.initials: E
authors.lastname: Demarsy
authors.forename: Martine
authors.initials: M
authors.lastname: Trevisan
authors.forename: Philip A
authors.initials: PA
authors.lastname: Davis
authors.forename: M Rob G
authors.initials: MR
authors.lastname: Roelfsema
authors.forename: Roger
authors.initials: R
authors.lastname: Hangarter
authors.forename: Christian
authors.initials: C
authors.lastname: Fankhauser
authors.forename: Claus
authors.initials: C
authors.lastname: Schwechheimer
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics / Q000528:radiation effects; D018546:Hypocotyl / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015151:Immunoblotting; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D009154:Mutation; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000528:radiation effects; D018524:Phototropism / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C423903:PHOT2 protein, Arabidopsis; C449300:PIN3 protein, Arabidopsis; C451260:PIN4 protein, Arabidopsis; C479554:PIN7 protein, Arabidopsis; D010750:Phosphoproteins; C585918:D6PK protein, Arabidopsis; D011494:Protein Kinases; C103646:NPH1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases