image: This is an Arabidopsis root tip after cold treatment showing the expression of two fluorescent copies of FLC (red and yellow). Every cell contains genes for red-FLC and yellow-FLC, but cells on the left (yellow) have turned red-FLC off while cells on the right (red) have turned yellow-FLC off. A few cells in the middle (orange) have both copies on. Patches of cells of the same colour descended from a common ancestor cell, showing that the on/off pattern is passed on through cell division. view more
Credit: Scott Berry, the John Innes Centre
New research findings by John Innes Centre (JIC) scientists have helped to settle an important debate in the field of epigenetic inheritance.
Using the flowering plant Arabidopsis thaliana as a model for their research, Professor Martin Howard, Professor Caroline Dean and members of their labs, have been trying to understand how organisms 'remember' past events at the cellular level.
Previous work showed that expression of a gene called FLC - a 'brake' to stop plants flowering until after winter - is repressed by cold exposure. Furthermore, the amount of repression is epigenetically 'remembered' after winter to permit flowering at the appropriate time. In many organisms, DNA is packaged around histone proteins to make a structure called chromatin. Intriguingly, the level of FLC repression is correlated with the level of cold-induced chemical modifications to the histones at the FLC gene, added by a protein complex called Polycomb Repressive Complex 2.
But are these histone modifications or other local features of the chromatin the cause of epigenetic memory, or are they a consequence of memory stored elsewhere? The findings of a new study published in the journal eLife provide compelling evidence that has helped to settle this long-standing debate.
Professor Martin Howard explains: "We engineered plant cells to contain two distinguishable copies of FLC - when one copy of the gene is expressed it generates a protein that glows red; when the other copy is expressed a yellow fluorescent protein is made. If epigenetic memory was inherited via the action of proteins freely diffusing inside a cell, then these proteins would affect both copies of FLC equally. As a result, either both copies of the gene would be expressed, leading to cells glowing red and yellow, or both copies of the gene would be repressed, giving cells that don't glow at all."
However, in these experiments, which were carried out by PhD student Scott Berry, cells glowing only red, or only yellow, were also observed, and this pattern of expression was epigenetically inherited through many cell divisions.
Professor Howard said: "The fact that two FLC copies in the same cell can have different heritable expression states shows that it is the local chromatin which must hold the epigenetic information passed from parent to daughter cells."
Although a flowering plant was used as the 'vehicle' to demonstrate these findings, epigenetic memory involving the Polycomb Repressive Complex can be found in many other organisms too. In particular, misregulation of Polycomb has been implicated in human cancers, thus these findings could have wide implications.
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This research was funded by the European Research Council (ERC), the Biotechnology and Biological Sciences Research Council (BBSRC) and the John Innes Foundation.
Notes to editors
1. The paper 'Local chromatin environment of a Polycomb target gene instructs its own epigenetic inheritance' is available online at: http://elifesciences.org/content/4/e07205
2. If you have any questions or would like to find out more please contact:
Geraldine Platten
Communications Manager at the John Innes Centre
T: 01603 450 238
E: Geraldine.platten@jic.ac.uk
3. Images to accompany this paper can be found at: http://bit.ly/1ANzLlY
4. About the John Innes Centre
Our mission is to generate knowledge of plants and microbes through innovative research, to train scientists for the future, to apply our knowledge of nature's diversity to benefit agriculture, the environment, human health and wellbeing, and engage with policy makers and the public.
To achieve these goals we establish pioneering long-term research objectives in plant and microbial science, with a focus on genetics. These objectives include promoting the translation of research through partnerships to develop improved crops and to make new products from microbes and plants for human health and other applications. We also create new approaches, technologies and resources that enable research advances and help industry to make new products. The knowledge, resources and trained researchers we generate help global societies address important challenges including providing sufficient and affordable food, making new products for human health and industrial applications, and developing sustainable bio-based manufacturing.
This provides a fertile environment for training the next generation of plant and microbial scientists, many of whom go on to careers in industry and academia, around the world.
The John Innes Centre is strategically funded by the Biotechnology and Biological Sciences Research Council (BBSRC). In 2013-2014 the John Innes Centre received a total of £31.4 million from the BBSRC
About the BBSRC
The Biotechnology and Biological Sciences Research Council (BBSRC) invests in world-class bioscience research and training on behalf of the UK public. Its aim is to further scientific knowledge, to promote economic growth, wealth and job creation and to improve quality of life in the UK and beyond.
Funded by Government, BBSRC invested over £484M in world-class bioscience in 2013-14.to supports research and training in universities and strategically funded institutes. BBSRC research and the people it funds are helping society to meet major challenges, including food security, green energy and healthier, longer lives. Research investments underpin important UK economic sectors, such as farming, food, industrial biotechnology and pharmaceuticals.
For more information about the BBSRC, its science and its impact see: http://www.bbsrc.ac.uk
5. Find out more about the European Research Council at: http://www.erc.europa.eu
6. Find out more about the John Innes Foundation at: http://www.johninnesfoundation.org.uk