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

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

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.