| 1. |
- Christoffer, Johnsson, et al.
(författare)
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Cambial stem cells and their niche
- 2016
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Ingår i: Plant Science. - : Elsevier BV. - 0168-9452. ; 252, s. 239-245
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Forskningsöversikt (refereegranskat)abstract
- Unlike animals, plants often have an indefinite genetic potency to form new organs throughout their entire lifespan. Growth and organogenesis are driven by cell divisions in meristems at distinct sites within the plant. Since the meristems contributing to axial thickening in dicots (cambia) are separated from places where axes elongate (apical meristems); there is a need of communication to coordinate growth. In their behavior, some meristematic cells resemble animal stem cells whose daughter cells either maintain the capacity to divide over a long period of time or undergo differentiation. The behavior of stem cells is regulated by their microenvironment, the so called niche. The stem- and niche-cell concept is now also widely accepted for apical meristems. An integral part of the cambial niche has recently been localized to the phloem. It steers cell division activity in the cambium via the release of a peptide signal and may be a hub to integrate signals from other stem cell populations to coordinate growth. Although these signals have yet to be determined, the discovery of the cambial niche cells will pave the way for a better understanding of inter-meristematic communication and cambial stem cell behavior. (C) 2016 Elsevier Ireland Ltd. All rights reserved.
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| 2. |
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| 3. |
- Christoffer, Johnsson, et al.
(författare)
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The plant hormone auxin directs timing of xylem development by inhibition of secondary cell wall deposition through repression of secondary wall NAC-domain transcription factors
- 2019
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 165, s. 673-689
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Tidskriftsartikel (refereegranskat)abstract
- Wood formation in higher plants is a complex and costly developmental process regulated by a complex network of transcription factors, short peptide signals and hormones. Correct spatiotemporal initiation of differentiation and downstream developmental stages is vital for proper wood formation. Members of the NAC (NAM, ATAF1/2 and CUC) family of transcription factors are described as top level regulators of xylem cell fate and secondary cell wall (SCW) deposition, but the signals initiating their transcription have yet to be elucidated. We found that treatment of Populus stems with auxin repressed transcription of NAC transcription factors associated with fiber and SCW formation and induced vessel-specific NACs, whereas gibberellic acid (GA) induced the expression of both classes of NAC domain transcription factors involved in wood formation. These transcriptional changes were reflected in alterations of stem anatomy, i.e. auxin treatment reduced cell wall thickness, whereas GA had a promotive effect on SCW deposition and on the rate of wood formation. Similar changes were observed on treatment of Arabidopsis thaliana stems with GA or the synthetic auxin NAA. We also observed corresponding changes in PIN5 overexpressing lines, where interference with auxin transport leads to premature SCW deposition and formation of additional fiber bundles. Together, this suggests wood formation is regulated by an integrated readout of both auxin and GA, which, in turn, controls expression of fiber and vessel specific NACs.
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| 4. |
- La Manno, Gioele, et al.
(författare)
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Molecular architecture of the developing mouse brain
- 2021
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 596:7870, s. 92-96
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Tidskriftsartikel (refereegranskat)abstract
- The mammalian brain develops through a complex interplay of spatial cues generated by diffusible morphogens, cell-cell interactions and intrinsic genetic programs that result in probably more than a thousand distinct cell types. A complete understanding of this process requires a systematic characterization of cell states over the entire spatiotemporal range of brain development. The ability of single-cell RNA sequencing and spatial transcriptomics to reveal the molecular heterogeneity of complex tissues has therefore been particularly powerful in the nervous system. Previous studies have explored development in specific brain regions(1-8), the whole adult brain(9) and even entire embryos(10). Here we report a comprehensive single-cell transcriptomic atlas of the embryonic mouse brain between gastrulation and birth. We identified almost eight hundred cellular states that describe a developmental program for the functional elements of the brain and its enclosing membranes, including the early neuroepithelium, region-specific secondary organizers, and both neurogenic and gliogenic progenitors. We also used in situ mRNA sequencing to map the spatial expression patterns of key developmental genes. Integrating the in situ data with our single-cell clusters revealed the precise spatial organization of neural progenitors during the patterning of the nervous system. A comprehensive single-cell transcriptomic atlas of the mouse brain between gastrulation and birth identifies hundreds of cellular states and reveals the spatiotemporal organization of brain development.
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| 5. |
- Sundell, David, et al.
(författare)
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AspWood : High-Spatial-Resolution Transcriptome Profiles Reveal Uncharacterized Modularity of Wood Formation in Populus tremula
- 2017
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Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 29:7, s. 1585-1604
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Tidskriftsartikel (refereegranskat)abstract
- Trees represent the largest terrestrial carbon sink and a renewable source of ligno-cellulose. There is significant scope for yield and quality improvement in these largely undomesticated species, and efforts to engineer elite varieties will benefit from improved understanding of the transcriptional network underlying cambial growth and wood formation. We generated high-spatial-resolution RNA sequencing data spanning the secondary phloem, vascular cambium, and wood-forming tissues of Populus tremula. The transcriptome comprised 28,294 expressed, annotated genes, 78 novel protein-coding genes, and 567 putative long intergenic noncoding RNAs. Most paralogs originating from the Salicaceae whole-genome duplication had diverged expression, with the exception of those highly expressed during secondary cell wall deposition. Coexpression network analyses revealed that regulation of the transcriptome underlying cambial growth and wood formation comprises numerous modules forming a continuum of active processes across the tissues. A comparative analysis revealed that a majority of these modules are conserved in Picea abies. The high spatial resolution of our data enabled identification of novel roles for characterized genes involved in xylan and cellulose biosynthesis, regulators of xylem vessel and fiber differentiation and lignification. An associated web resource (AspWood, http://aspwood.popgenie.org) provides interactive tools for exploring the expression profiles and coexpression network.
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| 6. |
- Sundell, David, et al.
(författare)
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High-spatial-resolution transcriptome profiling reveals uncharacterized regulatory complexity underlying cambial growth and wood formation in Populus tremula
- 2016
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Trees represent the largest terrestrial carbon sink and a renewable source of ligno-cellulose. There is significant scope for yield and quality improvement in these largely undomesticated species, however, efforts to engineer new, elite varieties are constrained by the lack of a comprehensive understanding of the transcriptional network underlying cambial growth and wood formation. We generated RNA Sequencing transcriptome data for four mature, wild-growing aspens (Populus tremula) from high-spatial-resolution tangential cryosection series spanning the secondary phloem, vascular cambium, expanding and secondary cell wall forming xylem cells, cell death zone and the previous years annual ring. The transcriptome comprised 28,294 expressed, previously annotated protein-coding genes, 78 novel protein-coding genes and 567 long intergenic non-coding RNAs. Most paralogs originating from the Salicaceae whole genome duplication had diverged expression, with the notable exception of those with high expression during secondary cell wall deposition. We performed co-expression network analysis to identify central transcriptional modules and associated several of these with known biological processes. This revealed previously uncharacterized complexity underlying the regulation of cambial growth and wood formation, with modules forming a continuum of activated processes across the tissues. The high spatial resolution suggested novel roles for known genes involved in xylan and cellulose biosynthesis, regulators of xylem vessel and fiber differentiation and components of lignification. The associated web resource (AspWood, http://aspwood.popgenie.org) integrates the data within a set of interactive tools for exploring the co-expression network of cambial growth and wood formation.
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| 7. |
- Wedin, Kevin, et al.
(författare)
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Automating nut tightening using Machine Learning
- 2020
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 53
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Konferensbidrag (refereegranskat)abstract
- At the Volvo Truck assembly plant the repetitive task of nut tightening is not ideal regarding quality and ergonomic. The solution to both these issues would be to significantly increase the level of automation. However, automating this specific station requires solutions to two specific problems. The first problem is to find and identify what nuts that need to be tightened, since they are not always on the same position for this highly customized product. The second problem is that the automated solution needs to accommodate the working space which is a moving assembly line with human operators. This paper investigates how these two problems ban be solved using machine learning and collaborative robots. A realistic mockup of the assembly station has been created at Stena Industry Innovation Laboratory (SII-Lab) where all the testing has been done. The problem to identify the nuts to tighten is further complicated by the fact that some nuts are placed backwards for future further assembly which must be avoided. Therefore, the selected solution is to use supervised machine learning for object recognition. This way, the system can be trained to recognize both nuts that need to be tightened and those mounted backwards, and possible other objects needed. Tests have been conducted with different types of CNN (Convolutional Neural Network) algorithms. Results have been very successful, and the test setup has successfully managed to connect the whole task of identifying the correct nuts and move the collaborative robot to that specific position.
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| 8. |
- Yanggratoke, Rerngvit, 1983-, et al.
(författare)
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A service-agnostic method for predicting service metrics in real-time
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We predict performance metrics of cloud services using statistical learning, whereby the behavior of a system is learned from observations. Specifically, we collect device and network statistics from a cloud testbed and apply regression methods to predict, in real-time, client-side service metrics for video streaming and key-value store services. Our method is service agnostic in the sense that it takes as input operating-systems and network statistics instead of service-specific metrics. We show that feature set reduction significantly improves the prediction accuracy in our case, while simultaneously reducing model computation time. We find that the prediction accuracy decreases when, instead of a single service, both services run on the same testbed simultaneously or when the network quality on the path between the server cluster and the client deteriorates. Finally, we discuss the design and implementation of a real-time analytics engine, which processes streams of device statistics and service metrics from testbed sensors and produces model predictions through online learning.
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