Project

Back to overview

Mechanisms of vernalization

English title Mechanisms of vernalization
Applicant Hennig Lars
Number 127358
Funding scheme ProDoc
Research institution Departement Umweltsystemwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Embryology, Developmental Biology
Start/End 01.10.2009 - 30.09.2012
Approved amount 197'914.00
Show all

Keywords (7)

arabidopsis; chromatin; development; vernalization; flowering; epigenetics; transcription factor

Lay Summary (English)

Lead
Lay summary
Vernalization, i.e. the increase of competence to flower brought about by prolonged exposure to low temperatures, is of great academic and economical interest. On the one hand side, vernalization is a well-documented process of a mitotic epigenetic cellular memory, and it is frequently used as an example to study dynamic chromatin changes during development. On the other hand, vernalization is an important agronomic trait, and vernalization-requiring (winter) varieties of temperate cereals and oil-seed rape have up to 30% higher yields than non-vernalization requiring summer varieties. Intensive research has uncovered many physiological and molecular details of vernalization responses. In Arabidopsis, the most upstream known effect of vernalization is transcriptional activation of VIN3 by extended exposure to cold. VIN3 is required to repress transcription of the floral repressor FLC. After return to ambient growth conditions, FLC is kept silent by the action of the VRN complex, which is similar to metazoan Polycomb repressive complex 2. Notably, FLC repression is stable only in dividing cells while in non-dividing cells FLC is initially repressed but re-activated when temperatures increase. Despite the great progress in understanding vernalization in recent years, several key questions concerning the molecular mechanisms of vernalization remain unsolved. Here, I propose to address two of the most prominent questions:
1.) Which genes are regulated by prolonged cold and function in vernalization besides FLC?
2.) Why are mitosis and/or DNA replication needed for stable repression of FLC and for efficient maintenance of the vernalized state?

I propose to perform the following experiments: Establish a reference dataset of transcript abundance and chromatin composition for vernalization genes during and after vernalization using RT-qPCR and ChIP. Test the importance of histone variants exchange for stable FLC repression. Identify physiological functions in the vernalization response of the known vernalization targets MAF3-5 and of six novel vernalization targets that were recently discovered in my laboratory. I expect that these results will be of great interest to the scientific community and to commercial plant breeders alike.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Annual meeting of the Swedish Society for Biochemistry and Molecular Biology (SFBM) 13.09.2011 Tällberg, Sweden
Chemical Side of SLU symposium 13.08.2011 Uppsala, Sweden
EPSO 2010 conference 13.08.2010 Lapland, Finland
Ph.D. student meeting, Université de Neuchâtel 13.04.2010 Neuchâtel, Switzerland


Abstract

Vernalization, i.e. the increase of competence to flower brought about by prolonged ex-posure to low temperatures, is of great academic and economical interest. On the one hand side, vernalization is a well-documented process of a mitotic epigenetic cellular memory, and it is frequently used as an example to study dynamic chromatin changes during development. On the other hand, vernalization is an important agronomic trait, and vernalization-requiring (winter) varieties of temperate cereals and oil-seed rape have up to 30% higher yields than non-vernalization requiring summer varieties. Intensive research has uncovered many physiological and molecular details of vernalization responses. In Arabidopsis, the most upstream known effect of vernalization is transcriptional activation of VIN3 by extended exposure to cold. VIN3 is required to repress transcription of the floral repressor FLC. After return to ambient growth conditions, FLC is kept silent by the action of the VRN complex, which is similar to metazoan Polycomb repressive complex 2. Notably, FLC repression is stable only in dividing cells while in non-dividing cells FLC is initially re-pressed but re-activated when temperatures increase. FLC has a prominent and central role in the vernalization response of Arabidopsis, but FLC is not the only gene involved be-cause flc mutants retain some vernalization responsiveness. Despite the great progress in understanding vernalization in recent years, several key questions concerning the molecu-lar mechanisms of vernalization remain unsolved. Here, I propose to address three of the most prominent questions:1.) Which genes are regulated by prolonged cold and function in vernalization besides FLC?2.) How is prolonged cold sensed and how does it regulate VIN3 transcription?3.) Why are mitosis and/or DNA replication needed for stable repression of FLC and for ef-ficient maintenance of the vernalized state?I propose to perform the following experiments: Establish a reference dataset of tran-script abundance and chromatin composition for vernalization genes during and after ver-nalization using RT-qPCR and ChIP. Test the importance of histone variants exchange for stable FLC repression using transgenic lines expressing epitope-tagged histone H3.1 and H3.2 variants and CAF-1 mutants. Identify sequence elements responsible for VIN3 induc-tion by prolonged cold using phylogenetic footprinting. Identify proteins that are involved in VIN3 induction by prolonged cold using yeast one-hybrid screens. Identify physiological functions in the vernalization response of the known vernalization targets MAF3-5 and of six novel vernalization targets that were recently discovered in my laboratory. Perform a genome-wide screening for genes regulated by vernalization using tiling DNA-microarrays.I expect that these results will be of great interest to the scientific community and to com-mercial plant breeders alike.
-