| 1. |
- Bhalerao, Rishikesh P., et al.
(författare)
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Auxin gradients across wood – instructive or incidental?
- 2014
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 151, s. 43-51
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Forskningsöversikt (refereegranskat)abstract
- Various aspects of wood formation have been linked to the action of auxin, e.g. cambial activity, dormancy, secondary cell wall deposition and tension wood formation. The presence of a radial auxin concentration gradient across wood-forming tissue has been suggested to regulate cambial activity and differentiation of cambial derivatives by providing positional information to cells within the tissue. Similar patterning mechanisms that depend on the interpretation of auxin thresholds have subsequently been proposed for shoot and root apical meristems. However, direct evidence for the existence of auxin gradients has only been obtained for the cambium of various tree species. While the auxin gradient theory is based on a plethora of descriptive and pharmacological experiments, in recent years, auxin function on wood formation has been underpinned by molecular and functional data. Here, we review the latest progress in understanding the role of auxin in wood formation and discuss how auxin concentration gradients could be established and interpreted in wood-forming tissues.
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| 2. |
- Bhalerao, Rishikesh P., et al.
(författare)
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Environmental and hormonal control of cambial stem cell dynamics
- 2017
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Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 68, s. 79-87
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Forskningsöversikt (refereegranskat)abstract
- Perennial trees have the amazing ability to adjust their growth rate to both adverse and favorable seasonally reoccurring environmental conditions over hundreds of years. In trunks and stems, the basis for the tuning of seasonal growth rate is the regulation of cambial stem cell activity. Cambial stem cell quiescence and dormancy protect the tree from potential physiological and genomic damage caused by adverse growing conditions and may permit a long lifespan. Cambial dormancy and longevity are both aspects of a tree's life for which the study of cambial stem cell behavior in the annual model plant Arabidopsis is inadequate. Recent functional analyses of hormone perception and catabolism mutants in Populus indicate that shoot-derived long-range signals, as well as local cues, steer cambial activity. Auxin is central to the regulation of cambial activity and probably also maintenance. Emerging genome editing and phenotyping technologies will enable the identification of down-stream targets of hormonal action and facilitate the genetic dissection of complex traits of cambial biology.
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| 3. |
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| 4. |
- 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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| 5. |
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| 6. |
- Hall, Hardy, et al.
(författare)
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Precision automation of cell type classification and sub-cellular fluorescence quantification from laser scanning confocal images
- 2016
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- While novel whole-plant phenotyping technologies have been successfully implemented into functional genomics and breeding programs, the potential of automated phenotyping with cellular resolution is largely unexploited. Laser scanning confocal microscopy has the potential to close this gap by providing spatially highly resolved images containing anatomic as well as chemical information on a subcellular basis. However, in the absence of automated methods, the assessment of the spatial patterns and abundance of fluorescent markers with subcellular resolution is still largely qualitative and time-consuming. Recent advances in image acquisition and analysis, coupled with improvements in microprocessor performance, have brought such automated methods within reach, so that information from thousands of cells per image for hundreds of images may be derived in an experimentally convenient time-frame. Here, we present a MATLAB-based analytical pipeline to (1) segment radial plant organs into individual cells, (2) classify cells into cell type categories based upon Random Forest classification, (3) divide each cell into sub-regions, and (4) quantify fluorescence intensity to a subcellular degree of precision for a separate fluorescence channel. In this research advance, we demonstrate the precision of this analytical process for the relatively complex tissues of Arabidopsis hypocotyls at various stages of development. High speed and robustness make our approach suitable for phenotyping of large collections of stem-like material and other tissue types.
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| 7. |
- Ikeda, Yoshihisa, et al.
(författare)
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Local auxin biosynthesis modulates gradient-directed planar polarity in Arabidopsis
- 2009
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Ingår i: Nature Cell Biology. - : Nature Publishing Group. - 1465-7392 .- 1476-4679. ; 11:6, s. 731-738
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Tidskriftsartikel (refereegranskat)abstract
- The coordination of cell polarity within the plane of a single tissue layer (planar polarity) is a crucial task during development of multicellular organisms. Mechanisms underlying establishment of planar polarity, however, differ substantially between plants and animals. In Arabidopsis thaliana, planar polarity of root-hair positioning along epidermal cells is coordinated towards maximum concentration of an auxin gradient in the root tip. This gradient has been hypothesized to be sink-driven and computational modelling suggests that auxin efflux carrier activity may be sufficient to generate the gradient in the absence of auxin biosynthesis in the root. Here, we demonstrate that the Raf-like kinase CONSTITUTIVE TRIPLE RESPONSE1 (CTR1; Refs 8, 9) acts as a concentration-dependent repressor of a biosynthesis-dependent auxin gradient that modulates planar polarity in the root tip. We analysed auxin biosynthesis and concentration gradients in a variety of root-hair-position mutants affected in CTR1 activity, auxin biosynthesis and transport. Our results reveal that planar polarity relies on influx- and efflux-carrier-mediated auxin redistribution from a local biosynthesis maximum. Thus, a local source of auxin biosynthesis contributes to gradient homeostasis during long-range coordination of cellular morphogenesis.
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| 8. |
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| 9. |
- 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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