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Elucidating the phytohormonal control of xylem development

Johnsson, Christoffer (2018). Elucidating the phytohormonal control of xylem development. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2018:20
ISBN 978-91-7760-180-7
eISBN 978-91-7760-181-4
[Doctoral thesis]

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Secondary xylem, commonly known as wood, has had a major impact on both our planet and civilization, its uses so ubiquitous that it is often taken for granted in daily life.
New challenges imposed by growing population and changing climate have led academia and industries to search for ways of altering wood characteristics to better suit specific purposes. Achieving this by genetic engineering requires the ability to alter gene expression in specific cell types, while avoiding alterations in others. This calls for an in depth understanding of the factors directing the differentiation and development of the cell types constituting secondary xylem.
Studies detailed in this thesis exhibit my attempts to link the signals of the phytohormones auxin and gibberellic acid to the formation of fibres, and their deposition of thick secondary cell walls. Using high resolution RNA-sequencing data gathered across developing Populus wood, I was able to illustrate that the expression profiles of various wood-associated transcription factors are distinct, in relation to their functions. Furthermore, I investigated the response of gene expression and tissue anatomy to treatment by auxin and gibberellin and found that auxin down-regulates transcription factors previously identified as master regulators of fibre secondary cell wall formation, as well as impede secondary wall development on a tissue level. At the same time, gibberellic acid appears to have a general enhancing effect on the expression of the same genes, and is better able to rescue the tissue phenotype of decapitated Populus plants.
I also highlight a role for gibberellic acid in the differentiation of fibre cells through DELLA regulated interaction of Class I KNOX transcription factors with proteins of the NUCLEAR FACTOR Y family.
These findings suggest that an integration of auxin and gibberellin signals, acting through multiple pathways, is responsible for the correct spatiotemporal differentiation and development of the secondary xylem.

Authors/Creators:Johnsson, Christoffer
Title:Elucidating the phytohormonal control of xylem development
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :March 2018
Depositing date:27 March 2018
Number of Pages:64
IChristoffer Johnsson, Urs Fischer* (2016). Cambial stem cells and their niche. Plant Science, 252 (2016), pp. 239-245.
IIDavid Sundell, Nathaniel R Street, Manoj Kumar, Ewa J Mellerowicz, Melis Kucukoglu, Christoffer Johnsson, Vikash Kumar, Chanaka Mannapperuma, Nicolas Delhomme, Ove Nilsson, Hannele Tuominen, Edouard Pesquet, Urs Fischer, Totte Niittylä, Bjorn Sundberg, Torgeir R Hvidsten* (2017). AspWood: High-spatial-resolution transcriptome profiles reveal uncharacterized modularity of wood formation in Populus tremula. Plant Cell, 29 (7), pp. 1585-1604
IIIChristoffer Johnsson, Xu Jin, Weiya Xue, Carole Dubreuil, Lina Lezhneva, Urs Fischer* (2018). 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. (Accepted)
IVChristoffer Johnsson, Lina Lezhneva, Daniela Liebsch, and Urs Fischer*. Class I KNOX transcription factors interact with the NF-FY complex to promote fibre differentiation in the hypocotyl (manuscript)
Place of Publication:Umeå
Publisher:Department of Forest Genetics and Plant Physiology
ISBN for printed version:978-91-7760-180-7
ISBN for electronic version:978-91-7760-181-4
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F62 Plant physiology - Growth and development
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Developmental Biology
(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 209 Industrial Biotechnology > Other Industrial Biotechnology
Agrovoc terms:xylem, auxins, gibberellins, cell differentiation, cell walls
Keywords:Xylem, Auxin, Gibberellin, differentiation, secondary cell wall
Permanent URL:
ID Code:15386
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Genetics and Plant Physiology
External funders:Stora Enso
Deposited By: Christoffer Johnsson
Deposited On:29 Mar 2018 09:12
Metadata Last Modified:09 Sep 2020 14:17

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