| 1. |
- Elfving, Nils, et al.
(author)
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The Arabidopsis thaliana Med25 mediator subunit integrates environmental cues to control plant development
- 2011
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 108:20, s. 8245-8250
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Journal article (peer-reviewed)abstract
- Development in plants is controlled by abiotic environmental cues such as day length, light quality, temperature, drought, and salinity. These signals are sensed by a variety of systems and transmitted by different signal transduction pathways. Ultimately, these pathways are integrated to control expression of specific target genes, which encode proteins that regulate development and differentiation. The molecular mechanisms for such integration have remained elusive. We here show that a linear 130-amino-acids-long sequence in the Med25 subunit of the Arabidopsis thaliana Mediator is a common target for the drought response element binding protein 2A, zinc finger homeodomain 1, and Myb-like transcription factors which are involved in different stress response pathways. In addition, our results show that Med25 together with drought response element binding protein 2A also function in repression of PhyB-mediated light signaling and thus integrate signals from different regulatory pathways.
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| 2. |
- Hörnblad, Emma, et al.
(author)
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Partial functional conservation of IRX10 homologs in physcomitrella patens and Arabidopsis thaliana indicates an evolutionary step contributing to vascular formation in land plants
- 2013
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In: BMC Plant Biology. - : Springer Science and Business Media LLC. - 1471-2229. ; 13
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Journal article (peer-reviewed)abstract
- Conclusions: The fact that the Physcomitrella IRX10 (PpGT47A) protein can partially complement an Arabidopsis irx10 irx10-L double mutant suggests that it shares some function with the Arabidopsis proteins, but the lack of a phenotype in knockout lines shows that the function is not required for growth or development under normal conditions in Physcomitrella. In contrast, the Arabidopsis irx10 and irx10 irx10-L mutants have strong phenotypes indicating an important function in growth and development. We conclude that the evolution of vascular plants has been associated with a significant change or adaptation in the function of the IRX10 gene family.
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| 3. |
- Murén, Eva, et al.
(author)
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Rescue and characterization of episomally replicating DNA from the moss Physcomitrella
- 2009
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:46, s. 19444-19449
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Journal article (peer-reviewed)abstract
- The moss Physcomitrella is unique among plants in that it permits efficient gene targeting by homologous recombination. Furthermore, transformed DNA can replicate episomally in Physcomitrella. Here we show that episomally replicating DNA can berescued back into E. coli, and use such rescue to study the fate of the transformed DNA. Significantly, plasmids rescued from moss transformed with circular DNA are identical to the original plasmid, whereas plasmids rescued from moss transformed with linearized DNA frequently have deletions created by direct repeat recombination.These events are highly predictable in that they target the longest direct repeat on the plasmid, if this repeat is at least 12 bp. Episomal transformants obtained with linearized DNA show a more than 1000-fold amplification of the DNA whereas transformants obtained with circular DNA have much lower copy numbers. Most episomal transformants quickly lose the plasmid in the absence of selection, but a semi-stable type of transformant that loses the plasmid at a much lower frequency was also observed. The consistent rescue of the original plasmid, or of predictable derivatives thereof, suggests that molecular genetics methods which rely on shuttle plasmids are feasible in Physcomitrella
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| 4. |
- Mälarstig, Anders, et al.
(author)
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Evaluation of circulating plasma proteins in breast cancer using Mendelian randomisation
- 2023
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In: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Journal article (peer-reviewed)abstract
- Biomarkers for early detection of breast cancer may complement population screening approaches to enable earlier and more precise treatment. The blood proteome is an important source for biomarker discovery but so far, few proteins have been identified with breast cancer risk. Here, we measure 2929 unique proteins in plasma from 598 women selected from the Karolinska Mammography Project to explore the association between protein levels, clinical characteristics, and gene variants, and to identify proteins with a causal role in breast cancer. We present 812 cis-acting protein quantitative trait loci for 737 proteins which are used as instruments in Mendelian randomisation analyses of breast cancer risk. Of those, we present five proteins (CD160, DNPH1, LAYN, LRRC37A2 and TLR1) that show a potential causal role in breast cancer risk with confirmatory results in independent cohorts. Our study suggests that these proteins should be further explored as biomarkers and potential drug targets in breast cancer.
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| 5. |
- Nilsson, Anders, et al.
(author)
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Two novel types of hexokinases in the moss Physcomitrella patens
- 2011
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In: BMC Plant Biology. - : Springer Science and Business Media LLC. - 1471-2229. ; 11
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Journal article (peer-reviewed)abstract
- Conclusions: We conclude that the hexokinase gene family is more diverse in Physcomitrella, encoding two additional types of hexokinases that are absent in vascular plants. In particular, the presence of a cytosolic and nuclear hexokinase (type C) sets Physcomitrella apart from vascular plants, and instead resembles yeast, where all hexokinases localize to the cytosol. The fact that all moss hexokinases are more similar to each other than to hexokinases from vascular plants, even though both type A and type B hexokinases are present in all plants, further suggests that the hexokinase gene family in Physcomitrella has undergone concerted evolution.
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| 6. |
- Nilsson, Anders, et al.
(author)
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Two novel types of plant hexokinases in the moss Physcomitrella patens
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Other publication (other academic/artistic)abstract
- Hexokinase catalyzes the phosphorylation of glucose and fructose, but it is also involved in sugar sensing in both fungi and plants. We have previously described two types of hexokinases in the moss Physcomitrella (Olsson et al., 2003, J. Biol. Chem. 278, 44439-44447). Type A, exemplified by the major Physcomitrella hexokinase PpHxk1, is a soluble protein that localizes to the chloroplast stroma. Type B, exemplified by PpHxk2, has an N-terminal membrane anchor. Both types are conserved also in seed plants, and localize to the chloroplast stroma and mitochondrial membranes, respectively. We have now characterized all eleven hexokinases encoded by the Physcomitrella genome. Based on their N-terminal sequences and intracellular localizations, three are type A hexokinases and four type B hexokinases. However, we also found two new types of hexokinases. Type C, encoded by a single gene, has neither transit peptide nor membrane anchor, and is found in the cytosol. Type D hexokinases, encoded by three genes, have membrane anchors and localize to mitochondrial membranes, but their sequences differ significantly from the type B hexokinases. Interestingly, all moss hexokinases are more similar to each other than to hexokinases from other plants. This suggests that the moss genes have undergone concerted evolution.
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| 7. |
- Ulfstedt, Mikael
(author)
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Functional studies of plant hexokinases and development of genetic methods in the moss Physcomitrella patens
- 2014
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Doctoral thesis (other academic/artistic)abstract
- In the field of biology, model systems are frequently used for practical reasons. Model organisms possess several features that make them easy to work with in a laboratory setting. In addition they usually have a host of established genetic tools that have been developed by the research community. This thesis explores the potential of adapting methods and tools used in the yeast Saccharomyces cerevisiae to the plant model system Physcomitrella patens. We have studied the fate and integrity of plasmids transformed into Physcomitrella with the purpose of developing a working shuttle plasmids system in moss. Other methods from yeast genetics such as the use of auxotrophic strains would also be useful if adapted to the Physcomitrella model system. Experiments using Physcomitrella patens showed that a histidine auxotrophic moss strain can be complemented with the wild type gene on a plasmid and that the plasmid can be rescued back into E. coli. This indicates that shuttle plasmids, auxotrophic marker genes such as PpHIS3, cloning by complementation and perhaps even dosage suppressor screens could be used in Physcomitrella patens. Furthermore this thesis investigates the hexose phosphorylating enzyme hexokinase in Physcomitrella patens as well as in the charophyte alga Klebsormidium nitens. The characterization and localization studies performed on the eleven Physcomitrella hexokinases led to the discovery of two new types of plant hexokinases, the type C and type D hexokinases. In addition to these two new types, Physcomitrella contained several of the previously described type A and type B hexokinases. In addition to its enzymatic function, hexokinases in both plants and fungi have been implicated in glucose sensing and signaling. This thesis examines if hexokinase 1 of the microalga Klebsormidium nitens may play a similar role in glucose sensing as observed in higher plants. With this purpose in mind transgenic lines of the Arabidopsis thaliana glucose insensitive mutant gin2-1 expressing the Klebsormidium nitens hexokinase 1 were created. It was found that the K. nitens hexokinase can complement the glucose signaling defect in the gin2-1 mutant.
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| 8. |
- Ulfstedt, Mikael, et al.
(author)
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Testing of Auxotrophic Selection Markers for Use in the Moss Physcomitrella Provides New Insights into the Mechanisms of Targeted Recombination
- 2017
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In: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 8
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Journal article (peer-reviewed)abstract
- The moss Physcomitrella patens is unique among plants in that homologous recombination can be used to knock out genes, just like in yeast. Furthermore, transformed plasmids can be rescued from Physcomitrella back into Escherichia coli, similar to yeast. In the present study, we have tested if a third important tool from yeast molecular genetics, auxotrophic selection markers, can be used in Physcomitrella. Two auxotrophic moss strains were made by knocking out the PpHIS3 gene encoding imidazoleglycerol-phosphate dehydratase, and the PpTRP1 gene encoding phosphoribosylanthranilate isomerase, disrupting the biosynthesis of histidine and tryptophan, respectively. The resulting PpHIS3 Delta and PpTRP1 Delta knockout strains were unable to grow on medium lacking histidine or tryptophan. The PpHIS3 Delta strain was used to test selection of transformants by complementation of an auxotrophic marker. We found that the PpHIS3 Delta strain could be complemented by transformation with a plasmid expressing the PpHIS3 gene from the CaMV 35S promoter, allowing the strain to grow on medium lacking histidine. Both linearized plasmids and circular supercoiled plasmids could complement the auxotrophic marker, and plasmids from both types of transformants could be rescued back into E. coli. Plasmids rescued from circular transformants were identical to the original plasmid, whereas plasmids rescued from linearized transformants had deletions generated by recombination between micro-homologies in the plasmids. Our results show that cloning by complementation of an auxotrophic marker works in Physcomitrella, which opens the door for using auxotrophic selection markers in moss molecular genetics. This will facilitate the adaptation of shuttle plasmid dependent methods from yeast molecular genetics for use in Physcomitrella.
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| 9. |
- Ulfstedt, Mikael, et al.
(author)
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The Ability of a Charophyte Alga Hexokinase to Restore Glucose Signaling and Glucose Repression of Gene Expression in a Glucose-Insensitive Arabidopsis Hexokinase Mutant Depends on Its Catalytic Activity
- 2018
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In: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 9
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Journal article (peer-reviewed)abstract
- Hexokinases is a family of proteins that is found in all eukaryotes. Hexokinases play key roles in the primary carbon metabolism, where they catalyze the phosphorylation of glucose and fructose, but they have also been shown to be involved in glucose signaling in both yeast and plants. We have characterized the Klebsormidium nitens KnHXK1 gene, the only hexokinase-encoding gene in this charophyte alga. The encoded protein, KnHXK1, is a type B plant hexokinase with an N-terminal membrane anchor localizing the protein to the mitochondrial membranes. We found that KnHXK1 expressed in Arabidopsis thaliana can restore the glucose sensing and glucose repression defects of the glucose-insensitive hexokinase mutant gin2-1. Interestingly, both functions require a catalytically active enzyme, since an inactive double mutant was unable to complement gin2-1. These findings differ from previous results on Arabidopsis AtHXK1 and its orthologs in rice, where catalytic and glucose sensing functions could be separated, but are consistent with recent results on the rice cytoplasmic hexokinase OsHXK7. A model with both catalytic and non-catalytic roles for hexokinases in glucose sensing and glucose repression is discussed.
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