| 1. |
- Horváth, Beatrix M, et al.
(författare)
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EBP1 regulates organ size through cell growth and proliferation in plants.
- 2006
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Ingår i: EMBO Journal. - : Wiley. - 0261-4189 .- 1460-2075. ; 25:20, s. 4909-20
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Tidskriftsartikel (refereegranskat)abstract
- Plant organ size shows remarkable uniformity within species indicating strong endogenous control. We have identified a plant growth regulatory gene, functionally and structurally homologous to human EBP1. Plant EBP1 levels are tightly regulated; gene expression is highest in developing organs and correlates with genes involved in ribosome biogenesis and function. EBP1 protein is stabilised by auxin. Elevating or decreasing EBP1 levels in transgenic plants results in a dose-dependent increase or reduction in organ growth, respectively. During early stages of organ development, EBP1 promotes cell proliferation, influences cell-size threshold for division and shortens the period of meristematic activity. In postmitotic cells, it enhances cell expansion. EBP1 is required for expression of cell cycle genes; CyclinD3;1, ribonucleotide reductase 2 and the cyclin-dependent kinase B1;1. The regulation of these genes by EBP1 is dose and auxin dependent and might rely on the effect of EBP1 to reduce RBR1 protein level. We argue that EBP1 is a conserved, dose-dependent regulator of cell growth that is connected to meristematic competence and cell proliferation via regulation of RBR1 level.
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| 2. |
- Magyar, Zoltan, et al.
(författare)
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Arabidopsis E2FA stimulates proliferation and endocycle separately through RBR-bound and RBR-free complexes
- 2012
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Ingår i: EMBO Journal. - New York, NY, USA : Nature Publishing Group. - 0261-4189 .- 1460-2075. ; 31:6, s. 1480-1493
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Tidskriftsartikel (refereegranskat)abstract
- Post-embryonic growth in plants depends on the continuous supply of undifferentiated cells within meristems. Proliferating cells maintain their competence for division by active repression of differentiation and the associated endocycle entry. We show by upregulation and downregulation of E2FA that it is required for maintaining proliferation, as well as for endocycle entry. While E2FB-RBR1 (retinoblastoma-related protein 1) complexes are reduced after sucrose addition or at elevated CYCD3;1 levels, E2FA maintains a stable complex with RBR1 in proliferating cells. Chromatin immunoprecipitation shows that RBR1 binds in the proximity of E2F promoter elements in CCS52A1 and CSS52A2 genes, central regulators for the switch from proliferation to endocycles. Overexpression of a truncated E2FA mutant (E2FA(Delta RB)) lacking the RBR1-binding domain interferes with RBR1 recruitment to promoters through E2FA, leading to decreased meristem size in roots, premature cell expansion and hyperactivated endocycle in leaves. E2F target genes, including CCS52A1 and CCS52A2, are upregulated in E2FADRB and e2fa knockout lines. These data suggest that E2FA in complex with RBR1 forms a repressor complex in proliferating cells to inhibit premature differentiation and endocycle entry. Thus, E2FA regulates organ growth via two distinct, sequentially operating pathways. The EMBO Journal (2012) 31, 1480-1493. doi:10.1038/emboj.2012.13; Published online 3 February 2012
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| 3. |
- Abraham, Edit, et al.
(författare)
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Immunodetection of retinoblastoma-related protein and its phosphorylated form in interphase and mitotic alfalfa cells
- 2011
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Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 62:6, s. 2155-2168
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Tidskriftsartikel (refereegranskat)abstract
- Plant retinoblastoma-related (RBR) proteins are primarily considered as key regulators of G(1)/S phase transition, with functional roles in a variety of cellular events during plant growth and organ development. Polyclonal antibody against the C-terminal region of the Arabidopsis RBR1 protein also specifically recognizes the alfalfa 115 kDa MsRBR protein, as shown by the antigen competition assay. The MsRBR protein was detected in all cell cycle phases, with a moderate increase in samples representing G(2)/M cells. Antibody against the human phospho-pRb peptide (Ser807/811) cross-reacted with the same 115 kDa MsRBR protein and with the in vitro phosphorylated MsRBR protein C-terminal fragment. Phospho-MsRBR protein was low in G(1) cells. Its amount increased upon entry into the S phase and remained high during the G(2)/M phases. Roscovitine treatment abolished the activity of alfalfa MsCDKA1;1 and MsCDKB2;1, and the phospho-MsRBR protein level was significantly decreased in the treated cells. Colchicine block increased the detected levels of both forms of MsRBR protein. Reduced levels of the MsRBR protein in cells at stationary phase or grown in hormone-free medium can be a sign of the division-dependent presence of plant RBR proteins. Immunolocalization of the phospho-MsRBR protein indicated spots of variable number and size in the labelled interphase nuclei and high signal intensity of nuclear granules in prophase. Structures similar to phospho-MsRBR proteins cannot be recognized in later mitotic phases. Based on the presented western blot and immunolocalization data, the possible involvement of RBR proteins in G(2)/M phase regulation in plant cells is discussed.
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| 4. |
- Baba, Kyoko, et al.
(författare)
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Activity-dormancy transition in the cambial meristem involves stage-specific modulation of auxin response in hybrid aspen.
- 2011
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 108:8, s. 3418-23
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Tidskriftsartikel (refereegranskat)abstract
- The molecular basis of short-day-induced growth cessation and dormancy in the meristems of perennial plants (e.g., forest trees growing in temperate and high-latitude regions) is poorly understood. Using global transcript profiling, we show distinct stage-specific alterations in auxin responsiveness of the transcriptome in the stem tissues during short-day-induced growth cessation and both the transition to and establishment of dormancy in the cambial meristem of hybrid aspen trees. This stage-specific modulation of auxin signaling appears to be controlled via distinct mechanisms. Whereas the induction of growth cessation in the cambium could involve induction of repressor auxin response factors (ARFs) and down-regulation of activator ARFs, dormancy is associated with perturbation of the activity of the SKP-Cullin-F-box(TIR) (SCF(TIR)) complex, leading to potential stabilization of repressor auxin (AUX)/indole-3-acetic acid (IAA) proteins. Although the role of hormones, such as abscisic acid (ABA) and gibberellic acid (GA), in growth cessation and dormancy is well established, our data now implicate auxin in this process. Importantly, in contrast to most developmental processes in which regulation by auxin involves changes in cellular auxin contents, day-length-regulated induction of cambial growth cessation and dormancy involves changes in auxin responses rather than auxin content.
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| 5. |
- Bako, Imre, et al.
(författare)
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Effects of H-bond asymmetry on the electronic properties of liquid water : An AIMD analysis
- 2019
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Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322 .- 1873-3166. ; 293
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Tidskriftsartikel (refereegranskat)abstract
- The effects of an asymmetric environment on the electronic properties of a water molecule in liquid water are in focus in this paper and were analysed from ab initio molecular dynamics simulations of liquid water at 300 and 350 K with the BLYP-D3 functional. We make the following observations. (1) The electronic DOS and the net molecular charge are more affected by the asymmetry of the water molecule's H-bond surroundings than by the number of H-bonded neighbours. The reverse is true for the dipole moment. (2) For all three properties, a 3-coordinated water molecule is more perturbed by accepting two H-bonds and donating one than by donating two and accepting one. (3) This order is not maintained in the calculated XES spectrum, which is less straightforward to interpret in terms of structure-property relationships than the DOS spectrum.
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| 6. |
- Burén, Stefan, et al.
(författare)
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Importance of post-translational modifications for functionality of a chloroplast-localized carbonic anhydrase (CAH1) in Arabidopsis thaliana
- 2011
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 6:6, s. e21021-
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundThe Arabidopsis CAH1 alpha-type carbonic anhydrase is one of the few plant proteins known to be targeted to the chloroplast through the secretory pathway. CAH1 is post-translationally modified at several residues by the attachment of N-glycans, resulting in a mature protein harbouring complex-type glycans. The reason of why trafficking through this non-canonical pathway is beneficial for certain chloroplast resident proteins is not yet known. Therefore, to elucidate the significance of glycosylation in trafficking and the effect of glycosylation on the stability and function of the protein, epitope-labelled wild type and mutated versions of CAH1 were expressed in plant cells.Methodology/Principal FindingsTransient expression of mutant CAH1 with disrupted glycosylation sites showed that the protein harbours four, or in certain cases five, N-glycans. While the wild type protein trafficked through the secretory pathway to the chloroplast, the non-glycosylated protein formed aggregates and associated with the ER chaperone BiP, indicating that glycosylation of CAH1 facilitates folding and ER-export. Using cysteine mutants we also assessed the role of disulphide bridge formation in the folding and stability of CAH1. We found that a disulphide bridge between cysteines at positions 27 and 191 in the mature protein was required for correct folding of the protein. Using a mass spectrometric approach we were able to measure the enzymatic activity of CAH1 protein. Under circumstances where protein N-glycosylation is blocked in vivo, the activity of CAH1 is completely inhibited.Conclusions/SignificanceWe show for the first time the importance of post-translational modifications such as N-glycosylation and intramolecular disulphide bridge formation in folding and trafficking of a protein from the secretory pathway to the chloroplast in higher plants. Requirements for these post-translational modifications for a fully functional native protein explain the need for an alternative route to the chloroplast.
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| 7. |
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| 8. |
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| 9. |
- Buren, Stefan, et al.
(författare)
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Use of the foot-and-mouth disease virus 2A peptide co-expression system to study intracellular protein trafficking in arabidopsis
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:12, s. e51973-
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Tidskriftsartikel (refereegranskat)abstract
- Background: A tool for stoichiometric co-expression of effector and target proteins to study intracellular protein trafficking processes has been provided by the so called 2A peptide technology. In this system, the 16-20 amino acid 2A peptide from RNA viruses allows synthesis of multiple gene products from single transcripts. However, so far the use of the 2A technology in plant systems has been limited.Methodology/Principal Findings: The aim of this work was to assess the suitability of the 2A peptide technology to study the effects exerted by dominant mutant forms of three small GTPase proteins, RABD2a, SAR1, and ARF1 on intracellular protein trafficking in plant cells. Special emphasis was given to CAH1 protein from Arabidopsis, which is trafficking to the chloroplast via a poorly characterized endoplasmic reticulum-to-Golgi pathway. Dominant negative mutants for these GTPases were co-expressed with fluorescent marker proteins as polyproteins separated by a 20 residue self-cleaving 2A peptide. Cleavage efficiency analysis of the generated polyproteins showed that functionality of the 2A peptide was influenced by several factors. This enabled us to design constructs with greatly increased cleavage efficiency compared to previous studies. The dominant negative GTPase variants resulting from cleavage of these 2A peptide constructs were found to be stable and active, and were successfully used to study the inhibitory effect on trafficking of the N-glycosylated CAH1 protein through the endomembrane system.Conclusions/Significance: We demonstrate that the 2A peptide is a suitable tool when studying plant intracellular protein trafficking and that transient protoplast and in planta expression of mutant forms of SAR1 and RABD2a disrupts CAH1 trafficking. Similarly, expression of dominant ARF1 mutants also caused inhibition of CAH1 trafficking to a different extent. These results indicate that early trafficking of the plastid glycoprotein CAH1 depends on canonical vesicular transport mechanisms operating between the endoplasmic reticulum and Golgi apparatus.
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| 10. |
- Caballero-Pérez, Juan, et al.
(författare)
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Transcriptional landscapes of Axolotl (Ambystoma mexicanum)
- 2018
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Ingår i: Developmental Biology. - : Elsevier. - 0012-1606 .- 1095-564X. ; 433:2, s. 227-239
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Tidskriftsartikel (refereegranskat)abstract
- The axolotl (Ambystoma mexicanum) is the vertebrate model system with the highest regeneration capacity. Experimental tools established over the past 100 years have been fundamental to start unraveling the cellular and molecular basis of tissue and limb regeneration. In the absence of a reference genome for the Axolotl, transcriptomic analysis become fundamental to understand the genetic basis of regeneration.Here we present one of the most diverse transcriptomic data sets for Axolotl by profiling coding and non coding RNAs from diverse tissues. We reconstructed a population of 115,906 putative protein coding mRNAs as full ORFs (including isoforms). We also identified 352 conserved miRNAs and 297 novel putative mature miRNAs.Systematic enrichment analysis of gene expression allowed us to identify tissue-specific protein-coding transcripts. We also found putative novel and conserved microRNAs which potentially target mRNAs which are reported as important disease candidates in heart and liver.
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