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Understanding the Molecular Basis of Differential Growth during Apical Hook Development

Jonsson, Kristoffer (2019). Understanding the Molecular Basis of Differential Growth during Apical Hook Development. Diss. (sammanfattning/summary) Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880
ISBN 978-91-7760-372-6
eISBN 978-91-7760-373-3
[Doctoral thesis]

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Abstract

Plants’ adaptation to their environment often involves change in development, which in many cases involves the establishment of differential growth rates across organs, for instance during phototropic and gravitropic responses. A striking example of differential growth is the formation of the apical hook, a structure that forms to protect the apical meristem as seedlings penetrate through soil. Coordination of differential growth across tissues is a multilayered process involving the combined effect of spatiotemporally controlled events such as gene expression, biosynthesis of proteins and polymers, transport and incorporation of biosynthetic products to their sites of participation, regulation of expansion driven by vacuolar turgor and control of cell mechanical properties via cell wall modifications.
This thesis addresses mechanisms that underlie differential growth, using the apical hook as a model. Particularly, this work focuses on the role of two distinct but interrelated processes; transport of components to the cell surface, and regulation of composition of components at the cell surface in apical hook development. This work demonstrates that secretion of different auxin carriers follow distinct routes from the trans-Golgi network (TGN) to the plasma membrane, where delivery of AUX1 but not PIN3 relies the TGN-localized protein ECHIDNA (ECH). Data show that the ECH-dependent secretory pathway is essential for ethylene-mediated differential growth of the apical hook in Arabidopsis. Moreover, this work investigates the mechanism by which ECH operates, and shows that ECH is required for the localization of the GTPase ARF1 and its activator GEFs BIG1-4, which are key components of a vesicle formation machinery at the TGN. ARF1 members and BIG1-4 are, like ECH, required for AUX1 delivery to the PM and for ethylene-mediated hook development. Finally, the thesis explores the role of the cell wall in differential growth, particularly, that of homogalacturonan pectin and its modification by methylesterification. This thesis demonstrates that differential cell elongation during hook development relies on establishing asymmetric cell wall mechanical properties across the hypocotyl via pectin methylesterification modifications in an auxin-dependent manner, and that a mechanochemical component provides feedback to the auxin machinery.
Taken together, this thesis demonstrates the multilayered regulation of growth asymmetry which facilitates shape generation.

Authors/Creators:Jonsson, Kristoffer
Title:Understanding the Molecular Basis of Differential Growth during Apical Hook Development
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2019
Number:2019:27
Number of Pages:74
Publisher:Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology
ISBN for printed version:978-91-7760-372-6
ISBN for electronic version:978-91-7760-373-3
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Article category:Other scientific
Version:Published version
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 404 Agricultural Biotechnology > Plant Biotechnology
(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Cell Biology
(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Developmental Biology
Keywords:Arabidopsis, differential growth, apical hook, secretion, TGN, auxin transport, ECHIDNA, cell wall, pectin, methylesterification
URN:NBN:urn:nbn:se:slu:epsilon-p-109974
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-109974
ID Code:21418
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Genetics and Plant Physiology
Deposited By: SLUpub Connector
Deposited On:21 Jan 2021 08:03
Metadata Last Modified:26 Jan 2021 08:00

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