Epigenetics

Epigenetics is one of the most exciting concepts in biology. Originally applied to a diverse collection of observations that could not be explained by Mendelian inheritance, the term is now more specifically used to describe heritable changes in gene expression that do not involve DNA mutation. Over the last decade is has become clear that these changes are caused by common biochemical modifications of chromatin, e.g. methylation of DNA and associated histone proteins. The best-studied epigenetic phenomenon is cell differentiation where different gene expression patterns are realised from a common genotype and then maintained within the cell lineage. Recent evidence from plants indicates that epigenetic changes induced by environmental stress can even be passed on from one generation to the next. Because epigenetic traits are based on reversible biochemical reactions that can ‘survive’ mitosis and meiosis they combine plasticity with inheritance.

So, was Lamarck with his theory of ‘heritability of acquired characteristics’ right after all? Has nature developed mechanisms for long-term memory of environmental stress conditions? And does this memory endow the plant and its progeny with an advantage when again confronted with the specific stress?

It is well known that plant stress tolerance can be improved through pre-exposure to the environmental stimulus but the molecular nature of this phenomenon remains largely unknown. One of the most intriguing aspects of epigenetic stress memory is that it closes a time-frame gap between short-lived physiological responses of an individual and evolutionary genome adaptation of a population. Considering that timescales of environmental changes span several orders of magnitude (from tides and seasons over occasional droughts and floods to geological and climate changes) it would be astonishing if nature had not developed molecular mechanisms for adaptation that operate on intermediate timescales.

In the Amtmann lab, we are testing the hypothesis that stress pre-treatments of plants cause modifications of DNA and chromatin structure that lead to an improved response to subsequent stress. In other words, we investigate whether epigenetic processes provide a molecular basis for memory and learning in plants.

Using a variety of experimental approaches we:

• characterise physiology and stress tolerance after priming
• measure transcriptional responses to priming and acute stress
• carry out genome-wide profiling of epigenetic modifications
• establish stability and heredity of specific chromatin modifications
• characterise novel genes of the epigenetic machinery
• compare epigenomes of sensitive and tolerant species (e.g. Arabidopsis thaliana and Thellungiella halophila)