title: Nuclear localization and interaction with COP1 are required for STO/BBX24 function during photomorphogenesis.
abstract: Arabidopsis (Arabidopsis thaliana) SALT TOLERANCE/B-BOX ZINC FINGER PROTEIN24 (STO/BBX24) is a negative regulator of the light signal transduction that localizes to the nucleus of plant cells and interacts with CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) in the yeast (Saccharomyces cerevisiae) two-hybrid system. The protein contains two B-box zinc-finger motives at the N terminus and a conserved motif at the C-terminal part required for the interaction with COP1. BBX24 accumulates during deetiolation of young seedlings in the first hours of exposure to light. However, this accumulation is transient and decreases after prolonged light irradiation. Here, we identified the amino acidic residues necessary for the nuclear import of the protein. In addition, we created mutated forms of the protein, and analyzed them by overexpression in the bbx24-1 mutant background. Our results indicate that the degradation of BBX24 occurs, or at least is initiated in the nucleus, and this nuclear localization is a prerequisite to fulfill its function in light signaling. Moreover, mutations in the region responsible for the interaction with COP1 revealed that a physical interaction of the proteins is also required for degradation of BBX24 in the light and for normal photomorphogenesis.
authors.affiliation: Faculty of Biology, Cell Biology, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Huili
authors.initials: H
authors.lastname: Yan
authors.forename: Katrin
authors.initials: K
authors.lastname: Marquardt
authors.forename: Martin
authors.initials: M
authors.lastname: Indorf
authors.forename: Dominic
authors.initials: D
authors.lastname: Jutt
authors.forename: Stefan
authors.initials: S
authors.lastname: Kircher
authors.forename: Gunther
authors.initials: G
authors.lastname: Neuhaus
authors.forename: Marta
authors.initials: M
authors.lastname: Rodríguez-Franco
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism* / Q000528:radiation effects; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008027:Light; D009024:Morphogenesis / Q000528:radiation effects*; D050505:Mutant Proteins / Q000378:metabolism; D019913:Nuclear Localization Signals / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding / Q000528:radiation effects; D021381:Protein Transport / Q000528:radiation effects; D059748:Proteolysis / Q000528:radiation effects; D012097:Repressor Proteins / Q000378:metabolism*; D017384:Sequence Deletion; D013347:Subcellular Fractions / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C585246:BBX24 protein, Arabidopsis; D050505:Mutant Proteins; D019913:Nuclear Localization Signals; D012097:Repressor Proteins; C100336:STO protein, Arabidopsis; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases