Plant Epigenetics Unit (Hidetoshi Saze)
Assistant Professor Hidetoshi Saze
hidetoshi.saze at oist.jp
Epigenetic Regulation of Gene Activity and Trans-generational Inheritance of Epigenetic Memory
Genetic information on genomic DNA is faithfully replicated and transmitted to the two daughter cells through mitosis. However, for differential expression of genes in various cell lineages during development, or for prompt responses to environmental stimuli, organisms further utilize epigenetic mechanisms that generate additional layers of heritable information on chromosome. Inheritance of the epigenetic information is mediated by modifications of chromatin, including DNA cytosine methylation, post-translational modifications of the core histone proteins and production of small RNA molecules. The epigenetic modifications can mediate both short-term (mitotic) and long-term (meiotic) transmission of active or inactive state of chromatin without changing the primary DNA sequence. Importantly, the epigenetic marks are heritable but potentially reversible, which therefore allow dynamic regulation of gene activities in response to surrounding environmental changes.
Plants offer ideal model systems for the studies of general epigenetic mechanisms and epigenetic inheritance of phenotypic variations. For instance, many epigenetic modifying factors found in other organisms are evolutionally conserved in plants. Moreover, detailed profiles of genome-wide gene expression and epigenetic states of the genome (epigenome) in various environmental conditions are now available for the model plants such as Arabidopsis and rice. By taking both genetics and genomics approach, we will explore the molecular mechanisms of epigenetic regulation of gene activity and trans-generational inheritance of epigenetic memory in plants.
By using the model plant Arabidopsis and other plant systems, we will address following key questions in epigenetics:
- How do cells distinguish between essential genes and parasitic transposons, and deposit the characteristic epigenetic modifications?
- What are the underlying molecular mechanisms of inheritance of epigenetic states of chromatin through cell divisions, or over multiple generations?
- How much of the phenotypic variations or complex traits are attributed not to conventional “genotype” but to the plastic “epigenotype”? Do the epigenotypes ultimately contribute to the genome evolution?
Trans-generational epigenetic inheritance of phenotypic variations has been reported in many organisms including plants and animals. Since plants conserve a wide range of epigenetic modifications, our studies could also have broader implications for epigenetic regulation of genome integrity and phenotypic variations in other organisms.
Le Tu N., Miyazaki Y., Takuno S., Saze H. (2015). Epigenetic regulation of intragenic transposable elements impacts gene transcription in Arabidopsis thaliana. Nucleic Acids Res., doi: 10.1093/nar/gkv258
Saze H., Kitayama J, Takashima K, Miura S, Harukawa Y, Ito T, Kakutani T. (2013). Mechanism for full-length RNA processing of Arabidopsis genes containing intragenic heterochromatin. Nat. Commun., 4:2301.
Saze, H., Shiraishi, A., Miura, A., and Kakutani, T. (2008). Control of genic DNA methylation by a jmjC-domain containing protein in Arabidopsis thaliana. Science 319, 462-465.
Saze, H. (2008). Epigenetic Memory Transmission through Mitosis and Meiosis in Plants. Semin. Cell Dev. Biol. 19, 527-536.
Saze, H., and Kakutani, T. (2007). Heritable epigenetic mutation of a transposon-flanked Arabidopsis gene due to lack of the chromatin-remodeling factor DDM1. EMBO J. 26, 3641-3652.
Saze, H., Mittelsten-Scheid, O., and Paszkowski, J. (2003). Maintenance of CpG methylation is essential for epigenetic inheritance during plant gametogenesis. Nat. Genet. 34, 65-69.