| 1. |
- Abele, H., et al.
(författare)
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Particle physics at the European Spallation Source
- 2023
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Ingår i: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 1023, s. 1-84
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Forskningsöversikt (refereegranskat)abstract
- Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world’s brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).
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| 2. |
- Backman, Filip, 1991-, et al.
(författare)
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The development of the NNBAR experiment
- 2022
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Ingår i: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 17:10
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Tidskriftsartikel (refereegranskat)abstract
- The NNBAR experiment for the European Spallation Source will search for free neutrons converting to antineutrons with a sensitivity improvement of three orders of magnitude compared to the last such search. This paper describes progress towards a conceptual design report for NNBAR. The design of a moderator, neutron reflector, beamline, shielding and annihilation detector is reported. The simulations used form part of a model which will be used for optimisation of the experiment design and quantification of its sensitivity.
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| 3. |
- Radhakrishnan, Guru V., et al.
(författare)
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An ancestral signalling pathway is conserved in intracellular symbioses-forming plant lineages
- 2020
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Ingår i: NATURE PLANTS. - : NATURE PUBLISHING GROUP. - 2055-026X .- 2055-0278. ; 6:3, s. 280-289
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Tidskriftsartikel (refereegranskat)abstract
- Plants are the foundation of terrestrial ecosystems, and their colonization of land was probably facilitated by mutualistic associations with arbuscular mycorrhizal fungi. Following this founding event, plant diversification has led to the emergence of a tremendous diversity of mutualistic symbioses with microorganisms, ranging from extracellular associations to the most intimate intracellular associations, where fungal or bacterial symbionts are hosted inside plant cells. Here, through analysis of 271 transcriptomes and 116 plant genomes spanning the entire land-plant diversity, we demonstrate that a common symbiosis signalling pathway co-evolved with intracellular endosymbioses, from the ancestral arbuscular mycorrhiza to the more recent ericoid and orchid mycorrhizae in angiosperms and ericoid-like associations of bryophytes. By contrast, species forming exclusively extracellular symbioses, such as ectomycorrhizae, and those forming associations with cyanobacteria, have lost this signalling pathway. This work unifies intracellular symbioses, revealing conservation in their evolution across 450 million yr of plant diversification. An extensive phylogenomics study based on hundreds of genomes and transcriptomes provides a new interpretation of the evolution of different types of symbiotic associations in land plants, and reveals a conserved ancestral symbiosis pathway.
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| 4. |
- Billhardt, Anja
(författare)
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Functional analyses of growth and development in the liverwort Marchantia polymorpha
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Land plants developed from a freshwater charophycean algae about 500 million years ago. Today, they consist of two main clades, the vascular plants and the non-vascular bryophytes including hornworts, liverworts and mosses. To adapt to challenges within a terrestrial habitat, the first land plants evolved a diversity of hormonal and genetic pathways regulating growth and development. Analyses regarding these networks are mainly based on the angiosperm Arabidopsis thaliana. Genes of other land plant lineages that are inexistent in Arabidopsis are often not considered in functional studies, resulting in an incomplete picture of land plant evolution. The remarkable phylogenetic position of bryophytes makes them interesting for studies of gene function as they might carry different characteristics compared to e.g. angiosperms. In difference to vascular plants, the liverwort Marchantia polymorpha harbors a small, low genetic redundant genome containing most gene families present in Arabidopsis. Thus making it an advantageous model organism to determining specific gene function. This thesis focuses on describing how dormancy and the circadian clock regulate growth in Marchantia. To avoid growth during unfavorable environmental, plants apply dormancy programs. Marchantia applies dormancy in gemmae, small asexual propagules produced by the shoot in a cup. Gemmae are dormant in the cup until they are dispersed by rain and subsequently germinating. I show that high levels of absisic acid (ABA), inhibits gemmae germination within the cup. Gemmae with a manipulated MpCYP707A, a gene involved in catabolism of ABA and seed dormancy regulation in Arabidopsis, showed altering dormancy suggesting that ABA homeostasis is fundamental for regulation of gemmae dormancy. Because dormant gemmae are not physically attached to the cup it has been speculated that the signal maintaining dormancy of gemmae is a gas. I found that gemmae mutated in positive and negative regulators of the ethylene signaling pathway showed decreased and increased dormancy respectively, suggesting that ethylene regulates dormancy through ABA.I also found that the circadian clock in Marchantia regulates growth of the thallus, possibly by affecting auxin levels. The circadian clock in land plants appears in structural differences between species. I showed that the gene MpDET1 has a conserved structure but harbors a different function compared to Arabidopsis. In Arabidopsis, growth is regulated by the clock through PIF genes, but in Marchantia, this pathway appears independent of PIF. Although the clock mechanism appear well conserved in land plants, its structure and function has evolved, creating diversity between land plant groups.
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| 5. |
- Lagercrantz, Ulf, et al.
(författare)
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DE‐ETIOLATED1 has a role in the circadian clock of the liverwort Marchantia polymorpha
- 2021
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 232:2, s. 595-609
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies of plant circadian clock evolution have often relied on clock models and genes defined in Arabidopsis. These studies identified homologues with seemingly conserved function, as well as frequent gene loss. In the present study, we aimed to identify candidate clock genes in the liverwort Marchantia polymorpha using a more unbiased approach.To identify genes with circadian rhythm we sequenced the transcriptomes of gemmalings in a time series in constant light conditions. Subsequently, we performed functional studies using loss-of-function mutants and gene expression reporters.Among the genes displaying circadian rhythm, a homologue to the transcriptional co-repressor Arabidopsis DE-ETIOLATED1 showed high amplitude and morning phase. Because AtDET1 is arrhythmic and associated with the morning gene function of AtCCA1/LHY, that lack a homologue in liverworts, we functionally studied DET1 in M. polymorpha.We found that the circadian rhythm of MpDET1 expression is disrupted in loss-of-function mutants of core clock genes and putative evening-complex genes. MpDET1 knock-down in turn results in altered circadian rhythm of nyctinastic thallus movement and clock gene expression. We could not detect any effect of MpDET1 knock-down on circadian response to light, suggesting that MpDET1 has a yet unknown function in the M. polymorpha circadian clock.
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| 6. |
- Lagercrantz, Ulf, et al.
(författare)
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Nyctinastic thallus movement in the liverwort Marchantia polymorpha is regulated by a circadian clock
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The circadian clock coordinates an organism’s growth, development and physiology with environmental factors. One illuminating example is the rhythmic growth of hypocotyls and cotyledons in Arabidopsis thaliana. Such daily oscillations in leaf position are often referred to as sleep movements or nyctinasty. Here, we report that plantlets of the liverwort Marchantia polymorpha show analogous rhythmic movements of thallus lobes, and that the circadian clock controls this rhythm, with auxin a likely output pathway affecting these movements. The mechanisms of this circadian clock are partly conserved as compared to angiosperms, with homologs to the core clock genes PRR, RVE and TOC1 forming a core transcriptional feedback loop also in M. polymorpha.
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| 7. |
- Lagercrantz, Ulf, et al.
(författare)
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PIF-independent regulation of growth by an evening complex in the liverwort Marchantia polymorpha
- 2022
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 17:6
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies in the liverwort Marchantia polymorpha have shown that the putative evening complex (EC) genes LUX ARRHYTHMO (LUX) and ELF4-LIKE (EFL) have a function in the liverwort circadian clock. Here, we studied the growth phenotypes of MpLUX and MpEFL loss-of-function mutants, to establish if PHYTOCHROME-INTERACTING FACTOR (PIF) and auxin act downstream of the M. polymorpha EC in a growth-related pathway similar to the one described for the flowering plant Arabidopsis. We examined growth rates and cell properties of loss-of-function mutants, analyzed protein-protein interactions and performed gene expression studies using reporter genes. Obtained data indicate that an EC can form in M. polymorpha and that this EC regulates growth of the thallus. Altered auxin levels in Mplux mutants could explain some of the phenotypes related to an increased thallus surface area. However, because MpPIF is not regulated by the EC, and because Mppif mutants do not show reduced growth, the growth phenotype of EC-mutants is likely not mediated via MpPIF. In Arabidopsis, the circadian clock regulates elongation growth via PIF and auxin, but this is likely not an evolutionarily conserved growth mechanism in land plants. Previous inventories of orthologs to Arabidopsis clock genes in various plant lineages showed that there is high levels of structural differences between clocks of different plant lineages. Here, we conclude that there is also variation in the output pathways used by the different plant clocks to control growth and development.
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| 8. |
- Linde, Anna-Malin, et al.
(författare)
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Rates and patterns of molecular evolution in bryophyte genomes, with focus on complex thalloid liverworts, Marchantiopsida
- 2021
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier. - 1055-7903 .- 1095-9513. ; 165
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Tidskriftsartikel (refereegranskat)abstract
- Plants commonly referred to as "bryophytes" belong to three major lineages of non-vascular plants: the liverworts, the hornworts and the mosses. They are unique among land plants in having a dominant haploid generation and a short-lived diploid sporophytic generation. The dynamics of selection acting on a haploid genome differs from those acting on a diploid genome: new mutations are directly exposed to selection. The general aim of this paper is to investigate the diversification rate of bryophytes - measured as silent site substitution rate representing neutral evolution (mutation rate) and the nonsynonymous to synonymous substitution rate ratio (dN/dS) representing selective evolution - and compare it with earlier studies on vascular plants. Results show that the silent site substitution rate is lower for liverworts as compared to angiosperms, but not as low as for gymnosperms. The selection pressure, measured as dN/dS, is not remarkably lower for bryophytes as compared to other diploid dominant plants as would be expected by the masking hypothesis, indicating that other factors are more important than ploidy.
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| 9. |
- Liu, Shujing, et al.
(författare)
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H2A ubiquitination is essential for Polycomb Repressive Complex 1-mediated gene regulation in Marchantia polymorpha
- 2021
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Ingår i: Genome Biology. - : BioMed Central (BMC). - 1465-6906 .- 1474-760X. ; 22:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Polycomb repressive complex 1 (PRC1) and PRC2 are chromatin regulators maintaining transcriptional repression. The deposition of H3 lysine 27 tri-methylation (H3K27me3) by PRC2 is known to be required for transcriptional repression, whereas the contribution of H2A ubiquitination (H2Aub) in the Polycomb repressive system remains unclear in plants. Results We directly test the requirement of H2Aub for gene regulation in Marchantia polymorpha by generating point mutations in H2A that prevent ubiquitination by PRC1. These mutants show reduced H3K27me3 levels on the same target sites as mutants defective in PRC1 subunits MpBMI1 and the homolog MpBMI1L, revealing that PRC1-catalyzed H2Aub is essential for Polycomb system function. Furthermore, by comparing transcriptome data between mutants in MpH2A and MpBMI1/1L, we demonstrate that H2Aub contributes to the PRC1-mediated transcriptional level of genes and transposable elements. Conclusion Together, our data demonstrates that H2Aub plays a direct role in H3K27me3 deposition and is required for PRC1-mediated transcriptional changes in both genes and transposable elements in Marchantia.
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| 10. |
- Ntefidou, Maria, et al.
(författare)
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Physcomitrium patens PpRIC, an ancestral CRIB-domain ROP effector, inhibits auxin-induced differentiation of apical initial cells
- 2023
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Ingår i: Cell Reports. - : Elsevier. - 2211-1247. ; 42:2
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Tidskriftsartikel (refereegranskat)abstract
- RHO guanosine triphosphatases are important eukaryotic regulators of cell differentiation and behavior. Plant ROP (RHO of plant) family members activate specific, incompletely characterized downstream signaling. The structurally simple land plant Physcomitrium patens is missing homologs of key animal and flowering plant RHO effectors but contains a single CRIB (CDC42/RAC interactive binding)-domain -contain-ing RIC (ROP-interacting CRIB-containing) protein (PpRIC). Protonemal P. patens filaments elongate based on regular division and PpROP-dependent tip growth of apical initial cells, which upon stimulation by the hor-mone auxin differentiate caulonemal characteristics. PpRIC interacts with active PpROP1, co-localizes with this protein at the plasma membrane at the tip of apical initial cells, and accumulates in the nucleus. Remark-ably, PpRIC is not required for tip growth but is targeted to the nucleus to block caulonema differentiation downstream of auxin-controlled gene expression. These observations establish functions of PpRIC in medi-ating crosstalk between ROP and auxin signaling, which contributes to the maintenance of apical initial cell identity.
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