Translational Dynamics of Leaf and Chloroplast Development in Maize

主要研究者： 爱丽丝·巴肯（俄勒冈州大学）CoPI：托马斯P.布鲁特内尔（唐纳德丹福斯植物科学中心）该项目将使用遗传和基因组方法，通过探索调控翻译如何有助于C4植物中二型叶绿体的分化以及在影响光合效率的光照条件下维持光合动态平衡，来开发“从基因组到系统水平的植物-环境相互作用的理解”。将重点放在玉米这一C4作物上特别有意义，因为C4光合作用可能演变为减少光呼吸，从而使植物更有效地利用氮和水。因此，更深入地了解驱动C4分化的调控网络将有助于增强天然C4植物和将C4性状工程化到C3作物中。在外联和培训方面，该项目将为高中生、本科生和研究生提供教育机会。 俄勒冈州大学本科生的实验室课程将与叶绿体生物发生中潜在缺陷的突变的大规模鉴定相结合。圣路易斯的一个项目将让中学生动手分析谷子的光合突变体。本科生，研究生和博士后学生将获得涉及尖端遗传，基因组和分子方法的指导研究经验。 最后，该项目将为更广泛的植物基因组学研究社区开发工具和资源，包括（1）~6000个新的序列索引Mu插入，可以通过MaizeGDB和内部搜索界面访问（http：//teosinte.uoregon.edu/mu-illumina/）;（2）推定的Mu标记等位基因的基因鉴定服务;（3）光合作用所必需的约100个玉米基因的功能注释和相关突变体库;（4）通过社区浏览器提供改进的基因组注释;以及（5）用于阐明共表达模块和相关功能推断的大规模翻译组和转录组数据集。叶绿体是植物中的亚细胞器，容纳光合作用和许多其他重要代谢过程的机器。叶绿体在不同的细胞类型中具有不同的形态和功能，例如C4植物的维管束鞘和叶肉细胞中的二型叶绿体。 它们是动态的细胞器，以优化光合性能同时最小化光氧化损伤的方式快速适应外部环境的变化。本计画将利用最先进的方法及大量的非光合作用突变体来阐明叶绿体的生物发生、分化及环境适应。选择玉米作为实验生物是因为它是具有二型叶绿体的C4植物，它提供了丰富的叶绿体生物发生突变体的集合，并且玉米叶片是描述分生组织细胞分化为光合活性叶细胞的发育过程的极好的实验系统。 该项目的具体目标是：（1）使用大规模正向遗传策略，为玉米中光合作用所需的约100个基因分配分子和生理功能;（2）使用最先进的核糖体分析策略，确定光合机构和维管束鞘和叶肉细胞中不同蛋白质组的安装所依据的翻译组动态;（3）提供光合叶组织分化过程中线粒体和质体基因表达进展的全面描述;（4）发现细胞质和叶绿体中受调节的翻译如何有助于在变化的光照条件下维持光合动态平衡。

PI: Alice Barkan (University of Oregon)CoPI: Thomas P. Brutnell (Donald Danforth Plant Science Center)This project will use genetic and genomic approaches to develop "a genome to systems-level understanding of plant-environmental interactions" by exploring how regulated translation contributes to the differentiation of the dimorphic chloroplasts in C4 plants and to maintaining photosynthetic homeostasis under shifting light conditions that compromise photosynthetic efficiency. The focus on maize, a C4 crop plant, is especially pertinent, as C4 photosynthesis likely evolved to reduce photorespiration, resulting in plants that use nitrogen and water more efficiently. Thus a deeper understanding of the regulatory networks driving C4 differentiation will aid in the enhancement of native C4 plants and in engineering C4 traits into C3 crops. With regard to outreach and training, the project will offer educational opportunities for high school, undergraduate and postgraduate students. A laboratory course for University of Oregon undergraduates will be integrated with the large-scale identification of mutations underlying defects in chloroplast biogenesis. A program in St. Louis will engage secondary school students in hands-on analysis of photosynthetic mutants in foxtail millet. Undergraduate, graduate, and postdoctoral students will gain mentored research experience involving cutting-edge genetic, genomic, and molecular approaches. Finally, the project will develop tools and resources for the broader plant genomics research community that include (1) ~6000 new sequence-indexed Mu insertions which can be accessed via MaizeGDB and an in-house search interface (http://teosinte.uoregon.edu/mu-illumina/); (2) a gene identification service for putative Mu-tagged alleles; (3) functional annotations and associated mutant stocks for ~100 maize genes that are essential for photosynthesis; (4) improved genome annotations to be made available through community browsers; and (5) large-scale translatome and transcriptome datasets for the elucidation of coexpression modules and associated functional inferences. Chloroplasts are subcellular organelles in plants that house the machinery for photosynthesis and numerous other essential metabolic processes. Chloroplasts acquire different forms and functions in different cell types, as exemplified by the dimorphic chloroplasts in the bundle sheath and mesophyll cells of C4 plants. They are dynamic organelles that adapt rapidly to changes in the external environment in a manner that optimizes photosynthetic performance while minimizing photo-oxidative damage. This project will elucidate the biogenesis, differentiation, and environmental adaptation of chloroplasts by employing state-of-the-art methods and an extensive collection of non-photosynthetic mutants. Maize is chosen as the experimental organism because it is a C4 plant with dimorphic chloroplasts, it offers a rich collection of chloroplast biogenesis mutants, and the maize leaf blade is an excellent experimental system for describing the developmental progression through which meristematic cells differentiate into photosynthetically-competent leaf cells. The specific objectives of the project are to (1) use a large-scale forward genetic strategy to assign molecular and physiological functions to ~100 genes in maize that are required for photosynthesis; (2) use a state-of-the-art ribosome profiling strategy to define the translatome dynamics underlying the installation of the photosynthetic apparatus and the distinct proteomes in bundle sheath and mesophyll cells; (3) provide a comprehensive description of the progression of mitochondrial and plastid gene expression during the differentiation of photosynthetic leaf tissue; and (4) discover how regulated translation in the cytosol and chloroplast contribute to maintaining photosynthetic homeostasis under shifting light conditions.