title: Directed dimerization: an in vivo expression system for functional studies of type II phytochromes.
abstract: Type II phytochromes (phy) in Arabidopsis form homodimers and heterodimers, resulting in a diverse collection of light-stable red/far-red (R/FR) sensing photoreceptors. We describe an in vivo protein engineering system and its use in characterizing the activities of these molecules. Using a phyB null mutant background, singly and doubly transgenic plants were generated that express fusion proteins containing the phyB-phyE N-terminal photosensory regions (NB-NE PSRs), a nuclear localization sequence, and small yeast protein domains that mediate either homodimerization or heterodimerization. Activity of NB/NB homodimers but not monomeric NB subunits in control of seedling and adult plant responses to R light is demonstrated. Heterodimers of the NB sequence with the chromophoreless NB(C357S) sequence, which mimic phyB Pfr/Pr photo-heterodimers, mediate R sensitivity in leaves and petioles but not hypocotyls. Homodimerization of the NC, ND and NE sequences and directed heterodimerization of these photosensory regions with the NB region reveal form-specific R-induced activities for different type II phy dimers. The experimental approach developed here of directed assembly of defined protein dimer combinations in vivo may be applicable to other systems.
authors.affiliation: Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.forename: Robert A
authors.initials: RA
authors.lastname: Sharrock
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D051939:Phytochrome B / Q000235:genetics*; D030821:Plants, Genetically Modified; D055503:Protein Multimerization / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D029681:Arabidopsis Proteins; C073594:CDC24 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C052130:GAL4 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; C497952:PHYB protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D051939:Phytochrome B; C073129:BEM1 protein, S cerevisiae
keywords: Arabidopsis thaliana; heterodimer; photomorphogenesis; photoreceptor; quaternary structure; synthetic biology