Genomic and Functional Analysis of Circadian Rhythms and Growth Vigor in Maize

玉米昼夜节律和生长活力的基因组和功能分析

• 批准号: 1238048
• 负责人: Z. Jeffrey Chen
• 金额: $ 150万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-03-01 至 2018-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1238048&HistoricalAwards=false
• 关键词: Genomic; Functional; Analysis; Circadian; Rhythms

PI: Z. Jeffrey Chen (The University of Texas at Austin) CoPI: Frank G. Harmon (University of California - Berkeley/USDA-ARS) Biological clocks orchestrate spatial and temporal control of growth and metabolism, leading to synchronous interactions between circadian rhythms and metabolic homoeostasis. In plants, maintenance of robust circadian rhythms promotes growth and fitness. Hybrids formed between strains or allopolyploids formed between species often show hybrid vigor or heterosis: superior levels of growth, biomass, and fertility in the hybrids compared to the parents. The mechanisms underlying heterosis are poorly understood. A recent study found a direct link between growth vigor and the circadian clock. Alterations in the expression waveform of key circadian clock genes in Arabidopsis hybrids and allotetraploids promote metabolic outputs including chlorophyll biosynthesis and starch metabolism. Upregulation of light signaling, photosynthesis, and starch metabolic genes in hybrids results from epigenetic repression of the circadian clock repressor genes during the day that, in turn, causes upregulation of clock activators and downstream metabolic genes. Although diurnal rhythms in gene expression, photosynthesis, and starch metabolism have been documented in maize, it is unknown whether the circadian-mediated metabolic vigor found in Arabidopsis hybrids and allopolyploids is directly applicable to the improvement of hybrid crops such as maize. Maize is among the best organisms for studying heterosis. Moreover, maize performs C4 photosynthesis, characterized by anatomical and biochemical specialization that increases net carbon assimilation at high temperatures. Part of this specialization in C4 plants may involve clock-regulated metabolic pathways. This project will test how circadian rhythms control metabolism and development in maize, as well as how circadian and other regulatory networks affect growth vigor in maize hybrids. Specific objectives are to (1) determine direct targets of clock genes in biological pathways including metabolism in maize hybrids and their inbred parents; (2) test how circadian clock gene expression and growth vigor in maize hybrids are controlled at levels of chromatin and metabolism; and (3) elucidate molecular bases for circadian regulation of metabolism and growth vigor in maize inbreds and hybrids.The impact of this research is transformative for many fundamental areas of biology ranging from circadian rhythms, first discovered in heliotrope plants in 1726, to hybrid vigor or heterosis, a widespread phenomenon that has intrigued many scientists, including Charles Darwin. The results from this work impact directly on improvement of hybrid crops, most notably maize and sorghum, which are of great importance to agriculture, food security, biofuels, and human health. Mechanistic insights into circadian regulation of metabolic vigor in plant hybrids are also applicable to the circadian rhythms in metabolism and physiology found in other sexually reproducing organisms like humans. With regard to outreach and training, this project will provide summer student internships for future science teachers through the UTeach program. The University of Texas at Austin (UT Austin) developed the UTeach program, and many other institutions across the country have replicated it. In addition, the project will provide research training opportunities for Master of Science (MSc) students at Alcorn State University and Mississippi Valley State University, two Historically Black Colleges/Universities. Sequence data will be available for public through GEO, MaizeGDB, and Gramene. Requests for seed and information about germplasm generated in this project will be available through MaizeGDB.

PI: Z. Jeffrey Chen（德克萨斯大学奥斯汀分校）CoPI: Frank G. Harmon（加州大学伯克利分校/USDA-ARS）生物钟协调生长和代谢的空间和时间控制，导致昼夜节律和代谢平衡之间的同步相互作用。在植物中，维持强健的昼夜节律可以促进生长和健康。在品系之间形成的杂种或种在种之间形成的异源多倍体通常表现出杂种优势或杂种优势：与亲本相比，杂种的生长、生物量和育性水平更高。杂种优势的机制尚不清楚。最近的一项研究发现了生长活力和生物钟之间的直接联系。拟南芥杂种和异源四倍体中关键生物钟基因表达波形的改变促进了代谢输出，包括叶绿素生物合成和淀粉代谢。在杂交中，光信号、光合作用和淀粉代谢基因的上调是由于生物钟抑制基因在白天的表观遗传抑制，而这反过来又导致生物钟激活基因和下游代谢基因的上调。虽然玉米基因表达、光合作用和淀粉代谢的昼夜节律已被记录，但尚不清楚拟南芥杂种和异源多倍体中发现的昼夜节律介导的代谢活力是否直接适用于玉米等杂交作物的改良。玉米是研究杂种优势的最佳生物之一。此外，玉米进行C4光合作用，其特点是解剖和生化特化，增加了高温下的净碳同化。C4植物的这种专门化可能与生物钟调节的代谢途径有关。该项目将测试昼夜节律如何控制玉米的代谢和发育，以及昼夜节律和其他调节网络如何影响玉米杂交种的生长活力。具体目标是：(1)确定时钟基因在玉米杂交种及其近交亲本代谢等生物学途径中的直接靶点；(2)在染色质和代谢水平上检验玉米杂种生物钟基因表达和生长活力的调控机制；(3)阐明玉米自交系和杂交种代谢和生长活力昼夜调节的分子基础。这项研究对生物学的许多基础领域产生了革命性的影响，从1726年首次在向阳植物中发现的昼夜节律，到杂交活力或杂种优势，这是一种广泛存在的现象，引起了包括查尔斯·达尔文在内的许多科学家的兴趣。这项工作的结果直接影响到杂交作物的改良，尤其是玉米和高粱，这对农业、粮食安全、生物燃料和人类健康具有重要意义。对杂交植物代谢活力的昼夜节律调节机制的见解也适用于其他有性生殖生物（如人类）的新陈代谢和生理昼夜节律。在外联和培训方面，该项目将通过UTeach计划为未来的科学教师提供暑期学生实习机会。德克萨斯大学奥斯汀分校（UT Austin）开发了UTeach项目，全国许多其他机构都效仿了这一项目。此外，该项目将为奥尔康州立大学（Alcorn State University）和密西西比河谷州立大学（Mississippi Valley State University）两所历史悠久的黑人学院/大学的理科硕士（MSc）学生提供研究培训机会。序列数据将通过GEO、MaizeGDB和Gramene向公众开放。本项目产生的种子和种质信息的请求将通过MaizeGDB提供。