Project

Back to overview

Cytokinin signaling in embryonic stem-cell specification and female gametophyte development

English title Cytokinin signaling in embryonic stem-cell specification and female gametophyte development
Applicant Müller Bruno
Number 125118
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 01.10.2009 - 31.07.2013
Approved amount 279'696.00
Show all

All Disciplines (2)

Discipline
Botany
Genetics

Lay Summary (English)

Lead
Lay summary
Despite the essential role of plants to support animal life on earth, our understanding of developmental processes in plants is still fragmentary. Similar to animals, plants use a small number of signaling systems, such as the signaling circuitries triggered by the plant hormones cytokinin and auxin, for many and diverse developmental processes. Typically, plant hormones are small organic molecules, elusive to in situ detection. Therefore, reporter genes, which label all signal-receiving cells in vivo, have proved powerful tools to dissect fundamental developmental processes. To analyze a long-postulated function of cytokinin during embryonic pattern formation, I have constructed a novel synthetic sensor that labels the cytokinin-signaling cells in planta. Combined with targeted genetic manipulations I have discovered an antagonistic relation between auxin and cytokinin that is required for embryonic stem-cell specification. The aim of this project is to characterize the genetic regulatory network downstream of cytokinin signaling that governs embryonic stem-cell specification. In addition, taking advantage of the unique tools I have generated, I novel cytokinin functions during female gametophyte development will be analyzed. The proposed studies will be conducted in Arabidospsis thaliana, a dicot reference plant that offers excellent genetic, genomic, imaging, and tissue culture amenability. In short, the specific aims are to:(a) Identify and characterize the cytokinin target genes in the nascent embryonic root meristem(b) Describe the role of cytokinin signaling in gametophyte developmentData gleaned from this studies will afford a point of reference and toolbox to study cytokinin signaling in other developmental contexts, such as leaf senescence, stem-cell pool maintenance in the shoot, shoot and root branching, grain size control, defense against pathogens, just to name a few. Given the conservation of the cytokinin signaling mechanism in higher plants, the value of the proposed experiments will extend beyond the reference plant Arabidopsis thaliana to include crop plants such as rice, wheat, or maize.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
A robust and sensitive synthetic sensor to monitor the transcriptional output of the cytokinin signaling network in planta
Zürcher E, Tavor-Deslex D, Lituiev D, Enkerli K, Tarr PT, Müller B (2013), A robust and sensitive synthetic sensor to monitor the transcriptional output of the cytokinin signaling network in planta, in Plant Physiology, 161(3), 1066.
Generic signal-specific responses: cytokinin and context-dependent cellular responses
Müller Bruno (2011), Generic signal-specific responses: cytokinin and context-dependent cellular responses, in Journal of Experimental Botany, 62(10), 3273-3286.
Model organisms--A historical perspective
Müller Bruno, Grossniklaus Ueli (2010), Model organisms--A historical perspective, in Journal of Proteomics, 73(11), 2054-2063.
Cytokinin Signaling Networks
Hwang Ildoo, Sheen Jen, Müller Bruno, Cytokinin Signaling Networks, in Annual Reviews in Plant Biology.

Associated projects

Number Title Start Funding scheme
102599 The role of hormone and glucose signaling in pattern formation during Arabidopsis thaliana embryonic development 01.10.2003 Fellowships for prospective researchers
133863 Live Cell Imaging to study dynamic developmental processes and protein-protein intertactions in planta 01.12.2011 R'EQUIP
149459 Defining Specificity in Cytokinin Ligand Localization and Signaling Interpretation 01.10.2013 Project funding (Div. I-III)

Abstract

1. Background. Gametogenesis and embryogenesis have been studied extensively in animal systems at the genetic, molecular, and cellular level. The results have provided insights into fundamental molecular mechanism involved in pattern formation. For example, a limited number of evolutionarily conserved signaling pathways was repeatedly found to be used for many diverse developmental functions. In contrast to animals, little is known about cell specification and differentiation during plant gametophytic and early embryonic development. Phytohormones such as auxin or cytokinin represent conserved signal transduction systems that participate in multiple and diverse aspects during a plant’s life. In the past years, auxin’s importance in early embryo development has been well documented. Very recently, we have characterized a novel role of cytokinin signaling in stem-cell specification during early embryogenesis. However, its precise action is not understood. Genetic evidence implies an essential role for cytokinin during female gametophyte development as well. Using Arabidopsis thaliana as a model system, this project focuses on characterizing the context-specific implementation of the cytokinin signaling pathway in cell specification during reproduction and embryogenesis of plants.2. Working Hypotheses. The general working hypotheses is formulated as follows: Visualization of cells that activate gene expression in response to conserved signaling cascades allows the description of signaling activity profiles in space and time during development. Identification of the gene products involved in generating and interpreting the signaling output will enable the formulation of working models. Tailored genetic approaches involving inducible transgenes and higher-order loss-of-function mutants will then be applied to test the models. 3. Specific Aims. (a) Identify and characterize the target genes of differential cytokinin signaling in nascent embryonic root stem cells. (b) Characterize the role of cytokinin signaling in the female gamete4. Experimental design and methods. An integrative approach combining genetic, genomic, and tissue culture tools will be applied. The majority of the methods rely on standard genetic and molecular biology protocols. Others rely on published protocols but need dedication and experience, such as the transient expression system using mesophyll protoplasts, or messenger RNA in-situ hybridization on sectioned tissue. Some need special adaptations and have been optimized for the study of the elusive and inaccessible early embryo and female gametophyte (e.g. micro-dissection techniques, in vitro ovule cultivation protocols).5. Expected Value. The experiments described in this proposal will provide a framework at the cellular and molecular resolution of how classical signalling pathways control pattern formation during plant development. For example, the results will provide a characterization of the cellular response to differential hormone signaling activities involved in embryonic stem-cell specification, establishing a case-study to illustrate how generic and fairly ubiquitous signalling pathways are involved in a specific and context-specific response. They will also provide insights into the poorly characterized functions of cytokinin in female gametophyte development, at unprecedented resolution. Data gleaned from this studies will afford a point of reference and toolbox to study cytokinin signaling in other developmental contexts, such as leaf senescence, stem-cell pool maintenance in the shoot, shoot and root branching, grain size control, defense against pathogens, just to name a few. Given the conservation of the cytokinin signaling mechanism in higher plants, the value of the proposed experiments will extend beyond the reference plant Arabidopsis thaliana to include crop plants such as rice, wheat, or maize.
-