title: The polarly localized D6 PROTEIN KINASE is required for efficient auxin transport in Arabidopsis thaliana.
abstract: The phytohormone auxin is a major determinant of plant growth and differentiation. Directional auxin transport and auxin responses are required for proper embryogenesis, organ formation, vascular development, and tropisms. Members of several protein families, including the PIN auxin efflux facilitators, have been implicated in auxin transport; however, the regulation of auxin transport by signaling proteins remains largely unexplored. We have studied a family of four highly homologous AGC protein kinases, which we designated the D6 protein kinases (D6PKs). We found that d6pk mutants have defects in lateral root initiation, root gravitropism, and shoot differentiation in axillary shoots, and that these phenotypes correlate with a reduction in auxin transport. Interestingly, D6PK localizes to the basal (lower) membrane of Arabidopsis root cells, where it colocalizes with PIN1, PIN2 and PIN4. D6PK and PIN1 interact genetically, and D6PK phosphorylates PIN proteins in vitro and in vivo. Taken together, our data show that D6PK is required for efficient auxin transport and suggest that PIN proteins are D6PK phosphorylation targets.
authors.affiliation: Tübingen University, Department of Developmental Genetics, Auf der Morgenstelle 5, 72076 Tübingen, Germany.
authors.forename: Melina
authors.initials: M
authors.lastname: Zourelidou
authors.forename: Isabel
authors.initials: I
authors.lastname: Müller
authors.forename: Björn C
authors.initials: BC
authors.lastname: Willige
authors.forename: Carola
authors.initials: C
authors.lastname: Nill
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Jikumaru
authors.forename: Hanbing
authors.initials: H
authors.lastname: Li
authors.forename: Claus
authors.initials: C
authors.lastname: Schwechheimer
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001692:Biological Transport; D016764:Cell Polarity; D018522:Gravitropism; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D050505:Mutant Proteins / Q000302:isolation & purification / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010766:Phosphorylation; D018517:Plant Roots / Q000166:cytology / Q000201:enzymology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D050505:Mutant Proteins; C116363:PIN1 protein, Arabidopsis; D011993:Recombinant Fusion Proteins