Using the plant seed as a model system, we study epigenetic regulation of developmental processes in the embryo and/or endosperm, but also how differentiation patters (or epigenetic patterns) established in the seed influence development and major developmental phase changes in the plant life cycle. Importantly, the development of the germline in most eukaryotes is accompanied by major epigenetic reprogramming that affect gene expression patterns and developmental paths in subsequent progeny. This leads towards a special focus on genomic imprinting, a phenomenon found in mammals and higher plants. Imprinting involves methylation of DNA and modifications of specific amino acid residues in histone tails leading to rearrangement of chromatin into parent-of-origin-specific repressive or permissive transcriptional states. In order to identify novel imprinted genes, the group has designed a genome-wide transcriptional screening strategy that allowed the identification of a cluster of previously uncharacterized AGAMOUS-LIKE (AGL) MADS-Box transcription factors as candidates for novel imprinted genes. Much of the group’s effort has been directed towards the verification of these genes and the elucidation of the epigenetic mechanisms regulating their imprinting. Imprinting has developed independently in mammalian and plant lineages, and although near to identical mechanistically, mammalian imprinted genes play a role in parental specific growth control whereas the biological role of imprinting in plants is more or less unknown. Interestingly, some imprinted genes, including AGL MADS-Box transcription factors in plants are sensitive to changes in ploidy ratio or are deregulated in interspecies crosses, and lead to post fertilization lethality in such crosses. This post-zygotic barrier is however partially lifted if these imprinted genes are mutated and thus non-functional. A current hypothesis is that plant imprinted genes are involved in ploidy sensing and may be part of a epigenetically based post-zygotic barrier that could have importance in speciation processes. We would like to understand the mechanistic (genetic and epigenetic) basis as well as the phenotypic consequence leading to this post-zygotic barrier (and eventually lifting of this barrier). Furthermore we would like to understand if this is a general phenomenon in plant and if similar mechanisms are operating in other eukaryotes.
Paul Grini Lab
Our focus is the developmental biology of plant reproduction, i.e. the generation of plant germlines from a somatic tissue, the differentiation and functional biology of plant gametes, culminating in double fertilization and the development of the embryo and the product of the second fertilization event, the endosperm inside the maternal structures of the seed.
Grini Lab Team at Finse, May 2015