The role of chromatin in alternating generations

Genes are encoded by DNA, which is supported by complex and dynamic assemblies of proteins that form the chromatin. Chromatin components play major roles in regulating gene expression and are expected to enable large scale coordinated changes in the activity of thousands of genes. Such events can take place during major life cycle transitions of multicellular organisms, such as puberty, molting, or senescence. It has remained difficult to address the global mechanisms associated with chromatin in such major transitions, largely due to the complexity of the networks involved. Here we propose to study this important aspect of life using a simpler experimental system that embodies one of the major steps in the evolution of Life on Earth. Five hundred million years ago, the first organisms evolved from aquatic ancestors to adapt to life on land, which required evolution of new functions and organs. In plants, this adaptation took place with the evolution of a new life stage, the sporophyte; today, this is commonly referred to as a plant. This proposal wishes to address the role of chromatin in the evolutionary origins of the sporophyte. To do so we will use Marchantia, a model species representative of basal land plants, which produces a simple sporophyte. We have obtained preliminary evidence for major changes in chromatin preceding the development of the Marchantia sporophyte. We will develop large-scale and high- throughput strategies based on common core facilities and team work possible at the Vienna Biocenter to address our scientific questions. These are based on molecular and genomic technologies, and on high-throughput microscopy. This parallel approach will enable for the first time to address in a global manner the role played by chromatin in life transitions in multicellular organisms. It will provide new paradigms and long term impact on our understanding on the role played by chromatin in gene regulation and evolutionary processes.