Histone H3 Phosphorylation and Gene Silencing in Chlamydomonas and Arabidopsis

智力上的功绩。多细胞生物的生长和发育是由它们的遗传组成和环境之间的复杂相互作用决定的。不同类型的细胞、组织和器官最终由不同的基因表达决定。每种特定的细胞类型只表达其遗传物质中包含的唯一信息的一部分，而其余的保持沉默。在某些情况下，这种基因沉默涉及可遗传(但可逆)的机制，称为表观遗传。表观遗传沉默可以通过染色质的共价化学修饰来发生，染色质是一种复杂的结构，由DNA包裹在被称为组蛋白的八聚体蛋白质周围。染色质领域的一个重大挑战是定义将组蛋白修饰与特定生物学结果联系起来的分子事件，如转录激活或沉默。一个额外的复杂程度是，共价组蛋白修饰的语言可能在进化上不同的生物体中不是通用的。这个项目将集中在组蛋白H3分子中相邻氨基酸发生的两种修饰--苏氨酸3的磷酸化(H3T3p)和赖氨酸4的甲基化(H3K4me)。目的是了解这些修饰是如何在两个不同的进化谱系中控制基因表达的，这两个进化谱系是绿藻莱茵衣藻和模式植物拟南芥在正常生长条件下和对环境变化的反应。研究重点将集中在研究负责磷酸化H3T3和去甲基化H3K4的酶，寻找与这些修饰氨基酸相互作用的蛋白质，并探索这些修饰在拟南芥对渗透胁迫反应中的作用。这些结果将有助于理解决定染色质沉默状态的分子机制，它们在进化上不同的谱系中的差异和/或相似之处，以及它们在环境应激下影响基因表达变化的作用。该项目将通过直接培训本科生和研究生以及一名博士后研究员，对人力资源开发产生影响。学生将通过实践经验学习研究方法，目的是培养他们对科学发现的兴趣。实验室的发现将被用来刺激学习过程，并在两门植物生物学课程中促进关于植物科学研究的好处的讨论。培训一名博士后从事研究和教育相结合的工作也是该项目的核心组成部分。此外，学生将参加一些致力于培训少数族裔个人的项目，以及与一个致力于教育公众了解科学的性质和重要性的非营利性组织的外联活动。除了提高我们在染色质生物学和组蛋白修饰机制进化方面的知识外，该项目的结果可能对农业具有实际意义。更好地理解表观遗传基因沉默机制可能会导致转基因技术的改进。此外，微藻正在成为生产可再生碳中性生物燃料的合适资源，更多地了解控制基因表达和新陈代谢的调节机制可能对它们的商业发展至关重要。

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.