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The role of auxin in abscission of organs and tissues

Jin, Xu (2015). The role of auxin in abscission of organs and tissues. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2015:54
ISBN 978-91-576-8306-9
eISBN 978-91-576-8307-6
[Doctoral thesis]

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Abstract

Most deciduous trees drop their leaves before winter, a process which is referred to as
leaf abscission. Leaf abscission is thought to be regulated by the action of auxin and
ethylene. In order to test the function of auxin in leaf abscission, an experimental
system in Populus was established to induce leaf shedding synchronously under
controlled greenhouse conditions. Exogenous auxin and an auxin transport inhibitor
delayed the abscission of dark-induced leaves and a new auxin response maximum
preceded the formation of an abscission zone. The analysis of microarray results
revealed that several genes encoding auxin transporters were strongly down-regulated
during abscission, suggesting their involvement in the formation of the auxin maximum
in the leaf axil. In ethylene-insensitive trees, leaf abscission could be delayed by the
application of auxin and ethylene signaling was not required for the regulation of gene
expression of auxin transporters during abscission. Thus, auxin and ethylene act partly
independently of each other on leaf abscission in Populus.

In order to study the effects of auxin on cell separation, isolated from its action on
the development of an abscission zone, we examined root cap abscission in
Arabidopsis. An auxin response gradient, spanning the root cap, was found to be
established prior to the separation of the outermost root cap layer. Inhibition of polar
auxin transport abolished the auxin response gradient in the root cap and disrupted
abscission. Intriguingly, auxin efflux carriers of the PIN family were not expressed in
the cell layer proximal to the abscising layer indicating that the outermost columella
tier is disconnected from the auxin source in the quiescent center.

A Populus homolog of the Arabidopsis WALLS ARE THIN1 (WAT1) was among
the most strongly regulated genes during abscission. We found that WAT1 localizes to
the tonoplast and facilitates auxin export from the vacuole. Whereas, WAT1-mediated
auxin homeostasis is needed for secondary wall deposition, wat1 mutants do not
display any phenotype related to abscission.

While auxin gradients have been implicated in various growth-related processes our
work provides novel data in support of a regulatory role of distinct auxin maxima and
minima in organ and tissue abscission.

Authors/Creators:Jin, Xu
Title:The role of auxin in abscission of organs and tissues
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :April 2015
Depositing date:2015
Volume:2015:54
Number of Pages:56
Papers/manuscripts:
NumberReferences
IXu Jin, Jorma Zimmermann, Andrea Polle and Urs Fischer (2015). Auxin is a long-range signal that acts independently of ethylene signaling on leaf abscission in Populus. submitted.
IIXu Jin, Urs Fischer. Establishment of a new auxin gradient prior to abscission of the lateral root cap. (Manuscript).
IIIPhilippe Ranocha, Oana Dima, Réka Nagy, Judith Felten, Claire Corratgé- Faillie, Ondřej Novák, Kris Morreel, Benoît Lacombe, Yves Martinez, Stephanie Pfrunder, Xu Jin, Jean-Pierre Renou, Jean-Baptiste Thibaud, Karin Ljung, Urs Fischer, Enrico Martinoia, Wout Boerjan and Deborah Goffner (2013). Arabidopsis WAT1 is a vacuolar auxin transport facilitator required for auxin homoeostasis. Nature Communications 4, 2625.
Place of Publication:Umeå
Publisher:Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8306-9
ISBN for electronic version:978-91-576-8307-6
ISSN:1652-6880
Language:English
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) > Biochemistry and Molecular Biology
(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Cell Biology
Agrovoc terms:populus, arabidopsis thaliana, auxins, ethylene, abscission, gene expression
Keywords:Populus, auxin, ethylene, abscission, cell separation, PIN proteins, Arabidopsis, root cap, auxin transport
URN:NBN:urn:nbn:se:slu:epsilon-e-2635
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-2635
ID Code:12194
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Genetics and Plant Physiology
Deposited By: Xu Jin
Deposited On:08 May 2015 13:27
Metadata Last Modified:06 Feb 2016 07:14

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