DISSERTATION RESEARCH: C4 Photosynthetic Evolution; Sub-types, Diversity, and Function within the Grass Tribe Paniceae

大多数植物使用被称为C3光合作用的过程将阳光转化为能量，但在白天温度较高的地区，第二种光合作用C4通常更有效。C4光合作用已经在至少60个不同的植物谱系中独立进化，其中包括在经济上重要的禾本科植物中的20多次进化。从C3到C4的转变在牧草部落Paniceae中尤其常见，该部落包含农作物珍珠小米和小米，以及潜在的生物燃料来源柳枝菊。本研究将使用多种互补的方法来更好地了解盘草科牧草的系统学和C4光合作用的进化。一名博士生将接受不同的系统发育、分子和计算建模技能培训，来自不同背景的高中生将在密苏里大学为期一天的研讨会上学习光合作用。更好地了解C4光合作用最终可能导致高产作物的发展。C4光合作用的多种独立派生导致了一组不同的光合作用亚型，其中许多亚型鲜为人知。Paniceae是弥补这一缺陷的理想系统，因为它的物种之间存在C4表型的多个来源。利用比较系统学、代谢网络模型和特定细胞类型的基因表达数据的新的整合，这项研究将有助于更好地理解Paniceae牧草之间的关系，以及C4光合作用的进化和功能。将解决的具体关键问题包括：C4光合作用是基因组和新陈代谢水平上的收敛进化的例子，还是只在表型上收敛？这三种C4光合作用生化亚型是从彼此进化而来的，还是各自独立起源的？两个或更多的C4光合作用生化亚型在多大程度上在一个有机体内共同作用，亚型混合的进化含义是什么？更好地了解C4光合作用将有助于未来研究作物改良，从而减少浪费和减少对环境的影响，并提高农业和生物能源系统的盈利能力。除了为C4光合作用的进化提供新的见解外，这项研究还为进一步研究其他复杂性状的进化提供了基础。

Most plants convert sunlight to energy using a process known as C3 photosynthesis, but in areas with higher daytime temperatures a second type of photosynthesis, C4, is often more efficient. C4 photosynthesis has evolved independently in at least sixty different plant lineages including over 20 times in the economically important grass family, Poaceae. Transitions from C3 to C4 are particularly common within the grass tribe Paniceae, which contains the crop plants pearl millet and foxtail millet, and the potential biofuel source, switchgrass. This research will use a variety of complementary approaches to better understand the systematics of Paniceae grasses and the evolution of C4 photosynthesis. One doctoral student will be trained in diverse phylogenetic, molecular and computational modeling skills, and high school students from diverse backgrounds will learn about photosynthesis at a one-day workshop at the University of Missouri. A better understanding of C4 photosynthesis could eventually lead to the development of higher yielding crops. The multiple independent derivations of C4 photosynthesis has resulted in a diverse group of photosynthetic subtypes, many of which are poorly understood. Paniceae is an ideal system for remedying this deficit because there are multiple origins of C4 phenotypes among its species. Using a novel integration of comparative phylogenomics, metabolic network modeling, and cell-type-specific gene expression data, this research will lead to a better understanding of the relationships among Paniceae grasses, and the evolution and function of C4 photosynthesis. Specific key questions that will be addressed include: Is C4 photosynthesis an example of convergent evolution on genomic and metabolomic levels or only phenotypically convergent? Have the three C4 photosynthesis biochemical sub-types evolved from one another or has each originated independently? To what extent do two or more C4 photosynthesis biochemical sub-types operate together within a single organism, and what are the evolutionary implications of sub-type mixing? A better understanding of C4 photosynthesis will facilitate future research on crop improvements that could lead to less waste and fewer environmental impacts, and increased profitability of agricultural and bioenergy systems. In addition to providing new insights into the evolution of C4 photosynthesis this research also provides a foundation for further work on the evolution of other complex traits.