| 11. |
- 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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| 12. |
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| 13. |
- Christoffer, Johnsson, et al.
(författare)
-
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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| 14. |
- Dubreuil, Carole, et al.
(författare)
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A local auxin gradient regulates root cap self-renewal and size homeostasis
- 2018
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Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 28:16, s. 2581-
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Tidskriftsartikel (refereegranskat)abstract
- Organ size homeostasis, compensatory growth to replace lost tissue, requires constant measurement of size and adjustment of growth rates. Morphogen gradients control organ and tissue sizes by regulating stem cell activity, cell differentiation, and removal in animals [1-3]. In plants, control of tissue size is of specific importance in root caps to protect the growing root tip from mechanical damage [4]. New root cap tissue is formed by the columella and lateral root-cap-epidermal stem cells, whose activity is regulated through non-dividing niche-like cells, the quiescent center (QC) [4, 5]. Columella daughter cells in contact with the QC retain the potency to divide, while derivatives oriented toward the mature cap undergo differentiation. The outermost columella layers are sequentially separated from the root body, involving remodeling of cell walls [6]. Factors regulating the balance between cell division, elongation, and separation to keep root cap size constant are currently unknown [4]. Here, we report that stem cell proliferation induced cell separation at the periphery of the root cap, resulting in tissue size homeostasis. An auxin response gradient with a maximum in the QC and a minimum in the detaching layer was established prior to the onset of cell separation. In agreement with a mathematical model, tissue size was positively regulated by the amount of auxin released from the source. Auxin transporters localized non-polarly to plasma membranes of the inner cap, partly isolating separating layers from the auxin source. Together, these results are in support of an auxin gradient measuring and regulating tissue size.
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| 15. |
- Dubreuil, Carole, et al.
(författare)
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The PIP Peptide of INFLORESCENCE DEFICIENT IN ABSCISSION Enhances Populus Leaf and Elaeis guineensis Fruit Abscission
- 2019
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Ingår i: Plants. - : MDPI AG. - 2223-7747. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The programmed loss of a plant organ is called abscission, which is an important cell separation process that occurs with different organs throughout the life of a plant. The use of floral organ abscission in Arabidopsis thaliana as a model has allowed greater understanding of the complexities of organ abscission, but whether the regulatory pathways are conserved throughout the plant kingdom and for all organ abscission types is unknown. One important pathway that has attracted much attention involves a peptide ligand-receptor signalling system that consists of the secreted peptide IDA (INFLORESCENCE DEFICIENT IN ABSCISSION) and at least two leucine-rich repeat (LRR) receptor-like kinases (RLK), HAESA (HAE) and HAESA-LIKE2 (HSL2). In the current study we examine the bioactive potential of IDA peptides in two different abscission processes, leaf abscission in Populus and ripe fruit abscission in oil palm, and find in both cases treatment with IDA peptides enhances cell separation and abscission of both organ types. Our results provide evidence to suggest that the IDA-HAE-HSL2 pathway is conserved and functions in these phylogenetically divergent dicot and monocot species during both leaf and fruit abscission, respectively.
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| 16. |
- Fischer, Urs, et al.
(författare)
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Lipid function in plant cell polarity.
- 2004
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Ingår i: Current opinion in plant biology. - : Elsevier BV. - 1369-5266 .- 1879-0356. ; 7:6, s. 670-6
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Tidskriftsartikel (refereegranskat)abstract
- The establishment and maintenance of cell polarity play pivotal roles during plant development. During the past five years, proteins that are required for different aspects of plant cell polarity have been identified. However, the functions of lipids and their interactions with proteins that mediate polarity remained largely unaddressed. Recent genetic studies have discovered cell and tissue polarity mutants that have defects in sterol composition, glycosylphosphatidylinositol-anchored proteins, glycosylphosphatidylinositol biosynthesis and phospholipid signalling. Analyses of the affected gene products have provided a first glance at the roles of lipids in cell polarity signalling, as well as in the trafficking and anchoring of polar proteins.
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| 17. |
- Fischer, Urs, et al.
(författare)
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Planar polarity of root hair positioning in Arabidopsis
- 2007
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Ingår i: Biochemical Society Transactions. - 0300-5127 .- 1470-8752. ; 35:Pt 1, s. 149-151
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Tidskriftsartikel (refereegranskat)abstract
- The co-ordinated polarity of cells within the plane of a single tissue layer (planar polarity) is intensively studied in animal epithelia but has only recently been systematically analysed in plants. The polar positioning of hairs in the root epidermis of Arabidopsis thaliana provides an easily accessible system for the functional dissection of a plant-specific planar polarity. Recently, mutants originally isolated in genetic screens for defects in root hair morphogenesis and changes in the sensitivity to or the production of the plant hormones auxin and ethylene have identified players that contribute to polar root hair placement. Here, we summarize and discuss recent progress in research on polar root hair positioning from studies in Arabidopsis.
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| 18. |
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| 19. |
- Fischer, Urs, et al.
(författare)
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The Dynamics of Cambial Stem Cell Activity
- 2019
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Ingår i: Annual Review of Plant Biology. - : Annual Reviews. - 1543-5008 .- 1545-2123. ; 70, s. 293-319
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Forskningsöversikt (refereegranskat)abstract
- Stem cell populations in meristematic tissues at distinct locations in the plant body provide the potency of continuous plant growth. Primary meristems, at the apices of the plant body, contribute mainly to the elongation of the main plant axes, whereas secondary meristems in lateral positions are responsible for the thickening of these axes. The stem cells of the vascular cambium-a secondary lateral meristem-produce the secondary phloem (bast) and secondary xylem (wood). The sites of primary and secondary growth are spatially separated, and mobile signals are expected to coordinate growth rates between apical and lateral stem cell populations. Although the underlying mechanisms have not yet been uncovered, it seems likely that hormones, peptides, and mechanical cues orchestrate primary and secondary growth. In this review, we highlight the current knowledge and recent discoveries of how cambial stem cell activity is regulated, with a focus on mobile signals and the response of cambial activity to environmental and stress factors.
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| 20. |
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