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Defining Specificity in Cytokinin Ligand Localization and Signaling Interpretation

English title Defining Specificity in Cytokinin Ligand Localization and Signaling Interpretation
Applicant Müller Bruno
Number 149459
Funding scheme Project funding (Div. I-III)
Research institution Institut für Pflanzen- und Mikrobiologie Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Botany
Start/End 01.10.2013 - 30.09.2017
Approved amount 450'779.00
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All Disciplines (4)

Discipline
Botany
Genetics
Molecular Biology
Embryology, Developmental Biology

Keywords (5)

cytokinin; signaling specificity; cytokinin transport; Arabidopsis; pattern formation

Lay Summary (German)

Lead
Zytokinine sind Pflanzenhormone mit vielfältigen essentiellen Funktionen in Pflanzen. Zytokinine aktivieren in Zielzellen eine Signalskaskade, welche das Zellverhalten steuert. Ein ungelöstes Problem besteht darin, welche Mechanismen bestimmen, wie die Zellen ausgewählt weden, welche auf das Signal reagieren. Wir untersuchen die Rolle von Zytokinin Transportern, welche die Signalantwort gezielt lokalisieren. Unabhängig davon haben wir beobachtet, dass Pflanzen über epigenetische Mechanismen eine Mutation kompensieren können, in einer Art von Selbstheilung. Wir beschreiben die molekularen Mechanismen, wie das reguliert wird.
Lay summary

Inhalt und Ziel des Forschungsprojekts

Für die neue Rolle von Zytokinin in der Entwicklung des embryonalen Wurzelstammzellsystems haben wir Zielgene identifiziert, deren funktionelle Rolle wir durch gezielte Tests analysieren werden. Das Ziel ist es, sowohl die Entwicklung des Stammzellsystems als auch die Rolle von Zytokinin besser zu verstehen.

Wir haben Mitglieder aus der Genfamilie von Purin Permeasen (PUP) identifiziert, welche für die Verteilung und den Transport von Zytokinin im Gewebe und den Zellen wichtig sind. Die vorgeschlagenen Projekte sollen deren Rolle für Zytokininantwort und die Pflanzenentwicklung beschreiben.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Zytokinine sind klassische Pflanzenhormone, welche in fundamentale Prozesse der Pflanzenentwicklung involviert sind. Ein besseres Verständnis der Zytokininsignalprozesse erlaubt ein besserer Verständnis der Pflanzenentwicklung, und also einen klügeren Umgang mit Pflanzen in der Landwirtschaft und Natur. Da Pflanzen als Nahrungsmittel und Sauerstoffproduzenten unabdingbar für das tierische und menschliche Leben auf diesem Planeten sind, ist dies hilfreich für die Menschen.

Direct link to Lay Summary Last update: 12.11.2017

Responsible applicant and co-applicants

Employees

Publications

Publication
Plant development regulated by cytokinin sinks
Evelyne Zürcher, Jingchun Liu, Martin di Donato, Markus Geisler, Bruno Müller (2016), Plant development regulated by cytokinin sinks, in Science, 353(6303), 1027-1030.
Cytokinin Synthesis, Signaling, and Function-Advances and New Insights
Zürcher Evelyne, Müller Bruno (2016), Cytokinin Synthesis, Signaling, and Function-Advances and New Insights, in International Review of Cell and Molecular Biology, 324, 1-32.

Collaboration

Group / person Country
Types of collaboration
Markus Geisler, Universität Fribourg Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Enrico Martinoia, Universität Zürich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Ulrich Hammes, Universität Regensburg Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Elliot Meyerowitz, California Institute of Technology United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
10th Tri-National Arabidopsis Meeting Poster PUP14 confines cytokinin responses throughout development 14.09.2017 Wien, Austria Müller Bruno; Zürcher Evelyne; Liu Jingchun;
XIX International Botanical Congress Talk given at a conference PUP14 confines cytokinin signaling 18.07.2017 Shenzen, China Müller Bruno;
At The Forefront Of Plant Research Poster Phenotypic compensation in ARABIDOPSIS RESPONSE REGULATOR 7(ARR7) permanent mutant, but not in inducible mutant 15.07.2017 Ghent, Belgium Liu Jingchun;
DMBV Vortragsserie Individual talk PUP14 confines cytokinin signaling throughout development 24.11.2016 Lausanne, Switzerland Müller Bruno;
Seminarreihe der Universität Fribourg Individual talk Cytokinin sinks control plant development 22.09.2016 Fribourg, Switzerland Müller Bruno;
8th PhD School in Plant Development in Retzbach 2015 Poster Purine Permeases and Cytokinin signaling 07.10.2015 Zellingen-Retzbach, Germany Zürcher Evelyne;
ACPD 2014, Auxins and Cytokinins in Plant Development, Talk given at a conference The role of PURINE PERMEASES in controlling cytokinin signaling domains 29.06.2014 Prag, Czech Republic Müller Bruno; Zürcher Evelyne;


Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Transporter PUP14 confines cytokinin signalling responses PCS newsletter International 2016
Media relations: print media, online media Wie Pflanzen sich entwickeln UZH News German-speaking Switzerland 2016

Awards

Title Year
Jahrespreis der Universität Zürich im Jahre 2017 2017

Associated projects

Number Title Start Funding scheme
164086 Imaging of Deep-Lying Tissues with Enhanced Resolution and Sensitivity to Study Plant Development 01.12.2015 R'EQUIP
125118 Cytokinin signaling in embryonic stem-cell specification and female gametophyte development 01.10.2009 Project funding (Div. I-III)

Abstract

Cytokinins are classic plant hormones that orchestrate plant growth, development, and physiology. They affect gene expression in target cells by activating a multistep phosphorelay network. The precise localization of cytokinin signaling activities in planta is of vital importance. However, very little is known how cytokinin is taken up by cells and transported in plants. Our experiments with Arabidopsis thaliana embryos suggest that cytokinins are actively distributed within the tissue, resulting in defined domains of cytokinin perception. Furthermore, we have identified members of the large gene family of purine permeases (PUP), encoding for transmembrane transporters that fulfill the postulated task. Specifically, from the 23 family members in Arabidopsis, we have identified previously uncharacterized members are expressed in an inverse pattern to the signaling response. Among these, PUP14 stands out as being highly expressed in contexts where cytokinin signaling occurs.These results suggest a model where selected PUP genes function to define the cytokinin signaling domains in planta. To corroborate and extend this model, we propose a comprehensive set of experiments (aim a), including:- Transport assays in mesophyll protoplast cells, yeast cells, and embryos- Extending the functional analyses of the PUP genes to all family members and different developmental contexts- Structure-function analyses to identify the protein domains involved in transport activity, substrate specificity, and subcellular localizationTo study the role of cytokinin in the establishment of the embryonic root stem cell system, as uncovered by our earlier study, we have identified cytokinin target genes using advanced tissue culture and microgenomics approaches, that await to be functionally characterized. Furthermore, in the course of our studies, we generated two different plants with the same genes inactivated, ARABIDOPSIS RESPONSE REGULATOR(ARR)7 and ARR15, but differing phenotypes: an inducible arr7,15 mutant displaying strong phenotypes in the nascent embryo root meristem, which affect the viability; and a steady arr7,15 mutant, that, while showing qualitatively similar phenotypes, recovers at later stages. We found that the steady mutant compensates by specifically and strongly upregulating a cytokinin-degrading enzyme, CYTOKININ OXIDASE2 (CKX2). Comparison of the two plants allows studying long known but little-understood mechanisms of developmental plasticity. We propose to (aim b): - Functionally characterize the cytokinin target genes in the nascent root stem-cell system- Genetically test the role of CKX2 in alleviating the phenotypes of the steady mutant, and to perform detailed characterizations to uncover timing and tissue-specificity of the compensatory strategy in the steady mutant.
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