title: The cytosolic kinases STY8, STY17, and STY46 are involved in chloroplast differentiation in Arabidopsis.
abstract: In Arabidopsis (Arabidopsis thaliana), transit peptides for chloroplast-destined preproteins can be phosphorylated by the protein kinases STY8, STY17, and STY46. In this study, we have investigated the in vitro properties of these plant-specific kinases. Characterization of the mechanistic functioning of STY8 led to the identification of an essential threonine in the activation segment, which is phosphorylated by an intramolecular mechanism. STY8 is inhibited by specific tyrosine kinase inhibitors, although it lacked the ability to phosphorylate tyrosine residues in vitro. In vivo analysis of sty8, sty17, and sty46 Arabidopsis knockout/knockdown mutants revealed a distinct function of the three kinases in the greening process and in the efficient differentiation of chloroplasts. Mutant plants displayed not only a delayed accumulation of chlorophyll but also a reduction of nucleus-encoded chloroplast proteins and a retarded establishment of photosynthetic capacity during the first 6 h of deetiolation, supporting a role of cytosolic STY kinases in chloroplast differentiation.
authors.affiliation: Department of Biology I, Botany, Ludwig-Maximilians-Universität München, D-82152 Planegg-Martinsried, Germany.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Lamberti
authors.forename: Irene L
authors.initials: IL
authors.lastname: Gügel
authors.forename: Jörg
authors.initials: J
authors.lastname: Meurer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Soll
authors.forename: Serena
authors.initials: S
authors.lastname: Schwenkert
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010788:Photosynthesis; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D013912:Threonine; D017346:Protein Serine-Threonine Kinases; C000609130:STY17 protein, Arabidopsis; C000609129:STY8 protein, Arabidopsis