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Function of Arabidopsis RBR in stem cell differentiation and developmental transition

English title Function of Arabidopsis RBR in stem cell differentiation and developmental transition
Applicant Gruissem Wilhelm
Number 132971
Funding scheme Project funding (Div. I-III)
Research institution Departement Umweltsystemwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Molecular Biology
Start/End 01.10.2010 - 31.03.2014
Approved amount 755'000.00
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All Disciplines (2)

Discipline
Molecular Biology
Genetics

Keywords (7)

Arabidopsis; Retinoblastoma-related protein; stem cells; meristem; cell cycle; embryo-to-seedling transition; interacting protein

Lay Summary (English)

Lead
Lay summary
Lead
The Retinoblastoma gene (RB) continues to be of intense medical interest because of its role in tumor formation. This project investigates the RETINOBLASTOMA-RELATED (RBR) pathway in Arabidopsis to understand how the RBR protein connects physiological and developmental regulation with transcriptional responses and differentiation programs.
Background
The currently best-understood function of the RB protein is the regulation of the E2F/DP family of transcription factors during entry into the cell cycle. RB also interacts with a number of other regulatory proteins and transcription factors, but the biological significance of these interactions remains largely unknown. More recently RB has emerged as a key regulator of differentiation processes, although the underlying molecular and biological mechanisms are not well understood. The RB pathway is conserved in plants and the RB-related plant homolog RBR is essential during reproduction. RBR is also required for maintenance and differentiation of stem and pluripotent cell populations. During seedling establishment, which is a critical transition in plant development, RBR cooperates with the Polycomb repressive complex (PRC2) to permanently inactivate late embryo-specific genes. 
Scientific Goal
The project uses genetic and functional genomics approaches to understand how RBR controls plant stem cell maintenance and connects cell cycle regulation to differentiation processes and developmental transitions. This will identify novel genetic networks in which RBR functions, the mechanism by which RBR controls the embryo-to-seedling transition, and the functional consequences of RBR interactions with novel stress- and metabolism-related proteins. 
Significance
RBR is encoded by a single gene in Arabidopsis. Since most of plant development is post-embryonic, RBR represents a unique and genetically powerful system to advance our understanding of the RB/RBR pathway and its regulatory function in cell cycle control, cell differentiation and important developmental transitions. The project will provide new insights that may facilitate clinically relevant research and new agricultural applications, especially for the critical plant embryo-to-seedling transition.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Arabidopsis replacement histone variant H3.3 occupies promoters of regulated genes
Shu Huan, Nakamura Miyuki, Siretskiy Alexey, Borghi Lorenzo, Moraes Izabel, Wildhaber Thomas, Gruissem Wilhelm, Hennig Lars (2014), Arabidopsis replacement histone variant H3.3 occupies promoters of regulated genes, in Genome Biology, 15, R62.
Arabidopsis Retinoblastoma-related and Polycomb group proteins: cooperation during plant cell differentiation and development
Kuwabara Asuka, Gruissem Wilhelm (2014), Arabidopsis Retinoblastoma-related and Polycomb group proteins: cooperation during plant cell differentiation and development, in Journal of Experimental Botany, 65(10), 2667-2676.
Arabidopsis MSI1 connects LHP1 to PRC2 complexes
Derkacheva Maria, Steinbach Yvonne, Wildhaber Thomas, Mozgova Iva, Mahrez Walid, Nanni Paolo, Bischof Sylvain, Gruissem Wilhelm, Hennig Lars (2013), Arabidopsis MSI1 connects LHP1 to PRC2 complexes, in EMBO Journal, 32, 2073-2085.
Measuring Arabidopsis chromatin accessibility using DNase I-PCR and DNase I-ChIP assays
Shu Huan, Gruissem Wilhelm, Hennig Lars (2013), Measuring Arabidopsis chromatin accessibility using DNase I-PCR and DNase I-ChIP assays, in Plant Physiology, 162(4), 1794-1801.
Distinct modes of DNA accessibility in plant chromatin
Shu Huan, Wildhaber Thomas, Siretskiy Alexey, Gruissem Wilhelm, Hennig Lars (2012), Distinct modes of DNA accessibility in plant chromatin, in Nature Communications, 3, 1281.
Emerging roles of RETINOBLASTOMA-RELATED proteins in evolution and plant development
Gutzat Ruben Borghi Lorenzo Gruissem Wilhelm (2012), Emerging roles of RETINOBLASTOMA-RELATED proteins in evolution and plant development, in Trends in Plant Science, 17, 139-148.
Emerging roles of RETINOBLASTOMA-RELATED proteins in evolution and plant development.
Gutzat Ruben, Borghi Lorenzo, Gruissem Wilhelm (2012), Emerging roles of RETINOBLASTOMA-RELATED proteins in evolution and plant development., in Trends in plant science, 17(3), 139-48.
RETINOBLASTOMA-RELATED protein controls the transition to autotrophic development
Gutzat R Borghi L Fütterer J Bischof S Laizet Y Hennig L Feil R Lunn J and Gruissem W (2011), RETINOBLASTOMA-RELATED protein controls the transition to autotrophic development, in Development, 138, 2977-2986.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Third International RB Meeting Poster EXPLORING THE ROLE OF ARABIDOPSIS RBR IN STOMATAL PLURI-POTENT STEM CELLS 07.10.2013 Monterey, CA, United States of America Kuwabara Asuka;
Third International RB Meeting Talk given at a conference FUNCTION OF ARABIDOPSIS RBR IN CELL CYCLE REGULATION, STEM CELL MAINTENANCE AND DEVELOPMENTAL TRANSITIONS 07.10.2013 Monterey, CA, United States of America Gruissem Wilhelm;
Third International RB Meeting Poster FROM DARKNESS TO LIGHT: THE FUNCTION OF ARABIDOPSIS RBR DURING LIGHT-INDUCED DEVELOPMENT 07.10.2013 Monterey, CA, United States of America Morello Simona;
Society for Experimental Biology Conference Talk given at a conference FUNCTION OF ARABIDOPSIS RBR IN CELL CYCLE REGULATION, STEM CELL MAINTENANCE AND DEVELOPMENTAL TRANSITIONS 06.07.2013 Valencia, Spain Gruissem Wilhelm;
Society for Experimental Biology Conference Talk given at a conference Exploring the role of Arabidopsis RBR during stomata development 06.07.2013 Valencia, Spain Kuwabara Asuka;
Academia Engiadina Naturwissenschaftliches Forum Individual talk Pflanzen und Krebs: was macht eine Tumorsuppressor-Gen in Arabidopsis? 17.01.2012 Samedan, Switzerland Gruissem Wilhelm;
Skidmore College Distinguished Lecture Series Individual talk Function of the Retinoblastoma-related protein in plants 20.10.2011 Saratoga Springs, United States of America Gruissem Wilhelm;
Max-Planck-Institute for Developmental Biology Individual talk Dosage-sensitive functions of Arabidopsis RBR and genetic interactions with PRC2 in stem cell maintenance and development transitions 24.04.2011 Tübingen, Germany Gruissem Wilhelm;


Communication with the public

Communication Title Media Place Year
New media (web, blogs, podcasts, news feeds etc.) A Gene - a Life Swiss Plant Science Web Newsletter Italian-speaking Switzerland German-speaking Switzerland Western Switzerland Rhaeto-Romanic Switzerland International 2012

Associated projects

Number Title Start Funding scheme
109475 Function of Arabidopsis Retinoblastoma-related RBR in stem cell maintenance and DNA endoreduplication 01.10.2005 Project funding (Div. I-III)
145021 Advancing Quantitative and Post-Translational Modification Proteomics by Latest Generation Mass Spectrometry 01.07.2013 R'EQUIP
153000 Unravelling the Arabidopsis RBR complexome 01.04.2014 Project funding (Div. I-III)

Abstract

Background and working hypothesis. The Retinoblastoma gene (RB) continues to be of intense medical interest and the focus of considerable research efforts because of its role in tumor formation. The currently best-understood function of pRB is the regulation of the E2F/DP family of transcription factors during the transition from G1 to S. pRB also interacts with a number of other proteins and transcription factors, but the biological significance of these interactions remains largely unknown. More recently pRB has emerged as a key regulator of development and differentiation processes, although the underlying molecular and biological mechanisms are not well understood, partially because of functional redundancies of the pRB pathway in mammalian cells. We discovered that the pRB pathway is conserved in plants and that the pRB-related plant homolog RETINOBLASTOMA-RELATED (RBR) is essential during gametophyte development. Using triplex analysis and conditional loss-of-function mutants in Arabidopsis, we have established that RBR is haploid insufficient and required for maintenance and differentiation of stem and pluripotent cell populations. In addition, we discovered that RBR controls the critical transition of the heterotrophic embryo into the photosynthetically active autotrophic seedling by targeting PRC2-mediated H3K27me3-dependent inactivation of late embryo-specific genes. Similar to pRB, RBR interacts with a large number of proteins, several of which are novel and involved in metabolic pathways. We therefore hypothesize that RBR has a novel function, which connects metabolic status and cell cycle control with specific developmental processes.Specific aims. We propose to dissect the RBR pathway in Arabidopsis to understand how RBR connects physiological and developmental status with transcriptional responses and differentiation programs. Specifically, we expect to identify (1) novel genetic networks in which RBR functions, (2) the mechanism by which RBR controls the embryo-to-seedling transition, and (3) the functional consequences of RBR interactions with novel stress- and metabolism-related proteins.Experimental design. Our work will take advantage of genetic and biochemical tools, conditional mutants and functional genomics approaches, and genome-wide profiling technologies. Using conditional expression of RBR-RNAi and RBRcs mutants in combination with epistatic interactions and transcriptome analysis we will establish the genetic and transcriptional network that is targeted by RBR. This work will be complemented by assignment of transcription programs to RBR-dependent regulators. Genome-wide ChIP-Chip in combination with transcriptome analysis will identify genes that become inactivated by RBR/PRC2-mediated H3K27me3 chromatin modification and promoters that are directly targeted by RBR. Mutants in specific metabolic pathways will be transformed with RBRi constructs to explore how RBR may connect metabolic functions to cell cycle regulation and development. We will validate selected RBR-interacting proteins using yeast 2-hybrid or split-YFP systems to expand the regulatory network in which RBR functions and open new research directions for the function of RBR outside of cell cycle control, both for the animal and plant fields as well as tumor biology.Expected value. Since RBR is encoded by a single gene in Arabidopsis and most of plant development is post-embryonic, Arabidopsis RBR represents a unique and genetically powerful system to advance our understanding of the pRB/RBR pathway and its regulatory function in cell cycle control, cell differentiation and important developmental transitions. Our proposed project will provide new insights that may facilitate clinically relevant research and new agricultural applications, especially for the critical embryo-to-seedling transition.
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