Intellectual Merit. The growth and development of multicellular organisms is determined by complex interactions between their genetic make-up and the environment. The different types of cells, tissues, and organs are ultimately defined by differential gene expression. Each particular cell type only expresses a unique fraction of the information contained in its genetic material, whereas the rest remains silenced. In some cases, this gene silencing involves heritable (but reversible) mechanisms, termed epigenetic. Epigenetic silencing can occur by covalent chemical modification of chromatin, the complex structure consisting of DNA wrapped around an octamer of proteins, known as histones. One significant challenge in the chromatin field is to define the molecular events that link histone modifications with specific biological outcomes, such as transcriptional activation or silencing. An added level of complexity is that the language of covalent histone modifications may not be universal across evolutionarily diverse organisms. This project will focus on two types of modification that occur on adjacent amino acids in the histone H3 molecule--phosphorylation of threonine 3 (H3T3p) and methylation of lysine 4 (H3K4me). The goals are to understand how these modifications control gene expression in two diverse evolutionary lineages, the green alga Chlamydomonas reinhardtii and the model plant Arabidopsis thaliana under normal growth conditions and in response to environmental change. Research will focus on studying the enzymes responsible for phosphorylating H3T3 and demethylating H3K4, searching for proteins that interact with these modified amino acids, and exploring the role of these modifications in response of Arabidopsis to osmotic stress. Results will contribute to the understanding of the molecular mechanisms involved in determining chromatin silencing states, their differences and/or similarities in evolutionarily divergent lineages, and their role in effecting changes in gene expression under environmental stresses.
Broader Impacts. The project will have an impact on human resource development through the direct training of undergraduate and graduate students and one postdoctoral fellow. Students will learn research methodology via hands on experience, with the goal of fostering their interest in scientific discovery. The laboratory findings will be used to stimulate the learning process and to promote discussions on the benefits of plant science research in two plant biology courses. The training of a postdoctoral fellow for a career which combines research and education is also a central component of the project. Additionally, students will participate in a number of programs devoted to the training of minority individuals and in outreach activities with a non-profit organization working to educate the public on the nature and importance of science. Besides advancing our knowledge in chromatin biology and the evolution of histone modifying mechanisms, the results from this project may have practical implications for agriculture. A better understanding of epigenetic gene silencing mechanisms may lead to improvements in transgenic technology. In addition, microalgae are emerging as a suitable resource for the production of renewable carbon-neutral biofuels and a greater knowledge of the regulatory mechanisms that control gene expression and metabolism may become crucial for their commercial development.
