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1.
Nature ; 502(7472): 455-7, 2013 Oct 24.
Article in English | MEDLINE | ID: mdl-24132239
2.
Nanoscale Res Lett ; 8(1): 338, 2013 Jul 29.
Article in English | MEDLINE | ID: mdl-23895295

ABSTRACT

Ferroelectric BaTiO3/SrTiO3 with optimized c-axis-oriented multilayered thin films were epitaxially fabricated on (001) MgO substrates. The microstructural studies indicate that the in-plane interface relationships between the films as well as the substrate are determined to be (001)SrTiO3//(001)BaTiO3//(001)MgO and [100]SrTiO3//[100]BaTiO3//[100]MgO. The microwave (5 to 18 GHz) dielectric measurements reveal that the multilayered thin films have excellent dielectric properties with large dielectric constant, low dielectric loss, and high dielectric tunability, which suggests that the as-grown ferroelectric multilayered thin films can be developed for room-temperature tunable microwave elements and related device applications.

3.
ACS Appl Mater Interfaces ; 4(11): 5761-5, 2012 Nov.
Article in English | MEDLINE | ID: mdl-23075425

ABSTRACT

Interface engineered BaTiO3/SrTiO3 heterostructures were epitaxially grown on (001) MgO substrates by pulsed laser deposition. Microstructural characterizations by X-ray diffraction and transmission electron microscopy indicate that the as-grown heterostructures are c-axis oriented with sharp interfaces. The interface relationships between the substrate and multilayered structures were determined to be [001](SrTiO3)//[001](BaTiO3)//[001](MgO) and (100)(SrTiO3)//(100)(BaTiO3)//(100)(MgO). The high-frequency microwave (∼18 GHz) dielectric measurements reveal that the dielectric constant and dielectric loss of the nanolayered heterostructures are highly dependent upon the stacking period numbers and layer thicknesses. With the increase in the periodic number, or the decrease in each layer thickness, the dielectric constant dramatically increases and the dielectric loss tangent rapidly decreases. The strong interface effect were found when the combination period is larger than 16, or each STO layer is less than 6.0 nm. The optimized dielectric performance was achieved with the best value for the loss tangent (0.02) and the dielectric constant (1320), which suggests that the BTO/STO heterostructures be promising for the development of the room-temperature tunable microwave elements.


Subject(s)
Barium Compounds/chemistry , Oxides/chemistry , Strontium/chemistry , Titanium/chemistry , Electric Impedance , Microwaves , Surface Properties
4.
Plant Mol Biol ; 76(1-2): 171-85, 2011 May.
Article in English | MEDLINE | ID: mdl-21547450

ABSTRACT

Live imaging during floral development revealed that expression of the DORNRÖSCHEN-LIKE (DRNL) gene encoding an AP2-like transcription factor, marks all organ founder cells. Transcription precedes the perception of auxin response maxima as measured by the DR5 reporter and is unaffected in early organogenesis, by mutation of four canonical auxin response elements (AuxREs) in the DRNL promoter. DRNL expression identifies discrete modes of organ initiation in the four floral whorls, from individual or pairs of organ anlagen in the outer whorl of sepals to two morphogenetic fields pre-patterning petals and lateral stamens, or a ring-shaped field giving rise to the medial stamens before carpel primordia are specified. DRNL function only overlaps in the central stem cell zone with that of its paralogue, DORNRÖSCHEN (DRN). drnl mutants are affected in floral organ outgrowth, which functionally interplays with boundary specification as organ fusions are sensitized by loss of CUP-SHAPED COTYLEDON (CUC) gene activity, and synergistic interactions exist with mutants in local auxin biosynthesis and polar transport. DRNL apparently monitors and contributes to cellular decisions in the SAM and thus provides a novel molecular access to the interplay of founder cell specification, organ anlage and organogenesis in the SAM peripheral zone.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/metabolism , Flowers/metabolism , Indoleacetic Acids/metabolism , Transcription Factors/metabolism , Arabidopsis/genetics , Arabidopsis/growth & development , Arabidopsis Proteins/genetics , Flowers/genetics , Flowers/growth & development , Gene Expression Regulation, Developmental , Gene Expression Regulation, Plant , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Meristem/genetics , Meristem/growth & development , Meristem/metabolism , Microscopy, Confocal , Mutation , Transcription Factors/genetics
5.
Plant Mol Biol ; 75(3): 223-36, 2011 Feb.
Article in English | MEDLINE | ID: mdl-21161330

ABSTRACT

DORNRÖSCHEN (DRN) and DORNRÖSCHEN-LIKE (DRNL) encode AP2-domain transcription factors, which act redundantly in cotyledon organogenesis. A more detailed genetic study now integrates DRN and DRNL into the CUP-SHAPED COTYLEDON (CUC) regulatory network and places DRN and DRNL differentially within the auxin signalling network: DRNL function overlaps with that of PIN-FORMED1, and DRN with PINOID. DRN and DRNL act cell-autonomously and are co-expressed in the early globular embryo, whereas expression patterns diverge during later stages of embryogeny. Both genes synergize to provide essential patterning information in the apical embryo domain, to establish correct CUC, SHOOTMERISTEMLESS and WUSCHEL expression domains, which relates to the patterning of SAM anlagen to a central apical position to create two planes of bilateral symmetry in wild type Arabidopsis thaliana embryos.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/growth & development , Arabidopsis/metabolism , Body Patterning , Signal Transduction , Transcription Factors/metabolism , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Gene Expression Regulation, Plant , Indoleacetic Acids/metabolism , Mutation , Transcription Factors/genetics
6.
Development ; 136(10): 1643-51, 2009 May.
Article in English | MEDLINE | ID: mdl-19369397

ABSTRACT

DORNROSCHEN (DRN), which encodes a member of the AP2-type transcription factor family, contributes to auxin transport and perception in the Arabidopsis embryo. Live imaging performed with transcriptional or translational GFP fusions shows DRN to be activated in the apical cell after the first zygotic division, to act cell-autonomously and to be expressed in single cells extending laterally from the apical shoot stem-cell zone at the position of incipient leaf primordia. Here, we show that the Auxin response factor (ARF) MONOPTEROS (MP) directly controls DRN transcription in the tips of the embryonic cotyledons, which depends on the presence of canonical Auxin response elements (AuxREs), potential ARF-binding sites flanking the DRN transcription unit. Chromatin immunoprecipitation experiments show that MP binds in vivo to two AuxRE-spanning fragments in the DRN promoter, and that MP is required for expression of DRN in cotyledon tips. Hence, DRN represents a direct target of MP and functions downstream of MP in cotyledon development.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/metabolism , DNA-Binding Proteins/metabolism , Seeds/metabolism , Transcription Factors/metabolism , Arabidopsis/embryology , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Cotyledon/metabolism , DNA-Binding Proteins/genetics , Gene Expression Regulation, Plant , Mutation , Promoter Regions, Genetic , Protein Binding , Seeds/genetics , Transcription Factors/genetics
7.
Plant Mol Biol ; 69(1-2): 57-68, 2009 Jan.
Article in English | MEDLINE | ID: mdl-18830673

ABSTRACT

The BIM1 protein which has been implicated in brassinosteroid (BR) signal transduction was identified from a two hybrid screen using the N-terminus, including the AP2 domain, of the transcription factors DORNROESCHEN (DRN) and DORNROESCHEN-LIKE (DRNL) which control embryonic patterning. The protein-protein interaction between BIM1 and DRN or DRNL was confirmed by co-immunoprecipitation and for DRN also in vivo by bimolecular fluorescence complementation. BIM1 can also physically interact with PHAVOLUTA (PHV), another interaction partner of DRN and DRNL. Loss of BIM1 function results in embryo patterning defects at low penetrance, including cell division defects in the hypophyseal region and apical domain defects such as cotyledon fusion and polycotyledony, in addition to polyembryony. BIM1 expression overlaps with that of DRN and DRNL from early globular embryo stages onwards. Higher order mutants between bim1, drn, drnl and phv suggest that although BIM1 may act partially redundantly with DRN in early embryo development, all genes function within the same pathway determining cotyledon development, supporting the hypothesis that they participate in a multimeric transcription factor complex. A role of BIM1 in embryonic development not only implicates a function for brassinosteroids in this process, but the interaction of BIM1 with DRN, involved with auxin signalling, represents a possible point of hormonal crosstalk in embryonic patterning and the first example of an interaction of components of the auxin and BR signalling pathways.


Subject(s)
Arabidopsis Proteins/physiology , Arabidopsis/embryology , Seeds/growth & development , Signal Transduction/physiology , Transcription Factors/metabolism , Arabidopsis Proteins/metabolism , Base Sequence , Blotting, Western , DNA Primers , Immunoprecipitation , Microscopy, Confocal , Protein Binding , Seeds/metabolism , Two-Hybrid System Techniques
8.
Plant Signal Behav ; 3(1): 49-51, 2008 Jan.
Article in English | MEDLINE | ID: mdl-19704719

ABSTRACT

Appropriate embryonic patterning is amongst the most fundamental processes in plant development, necessary for the correct specification of root and shoot apical meristems which generate all post-germination organs of a plant. Many mutations have been characterized which disrupt embryonic pattern formation and many recent studies have focussed on the role of auxin in establishing apical-basal polarity. Our recent work has demonstrated the role of two redundant AP2 transcription factors, DORNROESCHEN (DRN) and DORNROESCHEN-LIKE (DRNL) in the control of embryo patterning, upstream of auxin perception and/or response and that DRN in turn, is regulated by auxin. We also suggest both genes are involved in the change from radial to bilateral symmetry in the globular embryo and are responsible for positional information of meristem-specific genes such as STM. The promiscuous interaction of DRN and DRNL proteins with the redundant family of class III HD-ZIP partners may represent a way by which embryonic cell specification can be controlled by combinations of transcription factor complexes, together with auxin.

9.
Development ; 134(9): 1653-62, 2007 May.
Article in English | MEDLINE | ID: mdl-17376809

ABSTRACT

DORNROSCHEN (DRN) (also known as ENHANCER OF SHOOT REGENERATION1; ESR1) and DRN-LIKE (DRNL; also known as ESR2) are two linked paralogues encoding AP2 domain-containing proteins. drn mutants show embryo cell patterning defects and, similarly to drnl mutants, disrupt cotyledon development at incomplete penetrance. drn drnl double mutants with weak or strong drnl alleles show more highly penetrant and extreme phenotypes, including a pin-like embryo without cotyledons, confirming a high degree of functional redundancy for the two genes in embryo patterning. Altered expression of PIN1::PIN1-GFP and DR5::GFP in drn mutant embryos places DRN upstream of auxin transport and response. A yeast two-hybrid screen with DRN followed by co-immunoprecipitation and bimolecular fluorescence complementation revealed PHAVOLUTA (PHV) to be a protein interaction partner in planta. drn phv double mutants show an increased penetrance of embryo cell division defects. DRNL can also interact with PHV and both DRN and DRNL can heterodimerise with additional members of the class III HD-ZIP family, PHABULOSA, REVOLUTA, CORONA and ATHB8. Interactions involve the PAS-like C-terminal regions of these proteins and the DRN/DRNL AP2 domain.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/embryology , Gene Expression Regulation, Plant , Homeodomain Proteins/metabolism , Transcription Factors/metabolism , Amino Acid Sequence , Arabidopsis/genetics , Arabidopsis/metabolism , Arabidopsis Proteins/chemistry , Arabidopsis Proteins/genetics , Cotyledon/embryology , Dimerization , Homeodomain Proteins/chemistry , Homeodomain Proteins/genetics , Indoleacetic Acids/metabolism , Molecular Sequence Data , Mutation , Protein Structure, Tertiary , Seeds/metabolism , Transcription Factors/chemistry , Transcription Factors/genetics , Two-Hybrid System Techniques
10.
Nucleic Acids Res ; 34(4): 1281-92, 2006.
Article in English | MEDLINE | ID: mdl-16513846

ABSTRACT

The gene SHOOT MERISTEMLESS (STM) is required for the initiation and the maintenance of the shoot apical meristem (SAM) in Arabidopsis and encodes a MEINOX/three amino acid loop extension (TALE)-HD-type transcription factor. Translational fusions with the green fluorescent protein showed that STM is not nuclear by default. In a yeast two-hybrid screen performed with a meristem-enriched cDNA library, three interacting BLH (Bel1-like homeodomain) transcription factors were identified. According to bimolecular fluorescence complementation, STM is targeted into the nuclear compartment through heterodimerization with BLH partner proteins, which are expressed in distinct SAM domains from the center to the periphery. On a functional level, overexpression experiments in transgenic Arabidopsis plants suggest that individual heterodimers provide distinct contributions. These results contribute to our understanding of the STM transcription factor function in the SAM and also shed new light on the evolution of the TALE-HD super gene family in animal and plant lineages.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/metabolism , Cell Nucleus/metabolism , Homeodomain Proteins/metabolism , Meristem/metabolism , Transcription Factors/metabolism , Active Transport, Cell Nucleus , Arabidopsis/anatomy & histology , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Dimerization , Homeodomain Proteins/genetics , Immunoprecipitation , Meristem/genetics , Plants, Genetically Modified/metabolism , Protein Structure, Tertiary , RNA, Plant/analysis , Transcription Factors/chemistry , Transcription Factors/genetics
11.
FEBS Lett ; 531(2): 309-13, 2002 Nov 06.
Article in English | MEDLINE | ID: mdl-12417332

ABSTRACT

Vascular endothelial growth factor (VEGF) is a potent angiogenic mediator in tissue repair. In non-healing human wounds plasmin cleaves and inactivates VEGF165. In the present study, we generated recombinant VEGF165 mutants resistant to plasmin proteolysis. Substitution of Arg110 with Ala110 or Gln110, and Ala111 with Pro111 yielded plasmin-resistant and biologically active VEGF165 mutants. In addition, substitution of Ala111 with Pro111 resulted in a substantial degree of stabilization when incubated in wound fluid obtained from non-healing wounds. These results suggest that the plasmin cleavage site Arg110/Ala111 and the carboxyl-terminal domain play an important role in the mitogenic activity of VEGF165.


Subject(s)
Endothelial Growth Factors/genetics , Endothelial Growth Factors/metabolism , Fibrinolysin/metabolism , Intercellular Signaling Peptides and Proteins/genetics , Intercellular Signaling Peptides and Proteins/metabolism , Lymphokines/genetics , Lymphokines/metabolism , Animals , COS Cells , Cell Division , Cells, Cultured , Dose-Response Relationship, Drug , Endothelial Growth Factors/chemistry , Endothelial Growth Factors/pharmacology , Humans , Intercellular Signaling Peptides and Proteins/chemistry , Intercellular Signaling Peptides and Proteins/pharmacology , Kinetics , Lymphokines/chemistry , Lymphokines/pharmacology , Mutagenesis, Site-Directed , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth Factors , Wound Healing
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