A systems-level analysis of drought and density response in the model C4 grass Setaria viridis
The need for novel crops in an emerging bioenergy economy presents many challenges and opportunities for plant scientists. Plant breeding has been successful at transforming weedy species into some of the highest yielding crops on the planet. The plant domestication has led, in part, to an anticipated delivery of up to 1 billion dry tons of lignocellulosic feedstocks into the energy economy by 2030. However, The success of modern food crop breeding suggests that even greater advances can be made by developing the next generation of bioenergy feedstocks from C4 grass species that have been to date subjected to little or no breeding. The challenge we face is to exponentially accelerate the crop improvement process so that we can meet this level of bioenergy feedstock production. To achieve this unprecedented goal, it will be necessary to rapidly advance the process of plant breeding through large-scale biology, computational biology and systems approaches. Therefore, the goal of this proposal was to understand how productivity, drought tolerance and water use efficiency (WUE) are regulated at the genomic level in order to inform metabolic engineering and molecular-assisted breeding efforts.This necessitates the use of a model species that is closely related to less genetically tractable feedstock grasses such as Sorghum, switchgrass and Miscanthus. To achieve this we have significantly enhanced the utility of Setaria viridis as a model C4 species for system biology. This was achieved through field, greenhouse and laboratory experiments to survey a breadth of environments and explore the potential of gene networks to predict physiological responses across environments. We challenged plants under abiotic stresses to examine the plasticity of the network and identify targets for future manipulation. Finally, we have identified promising new gene engineering technologies to modify genetic networks in this model C4 species to understand and enhance abiotic stress tolerance. The outcomes of this project led to 1) identification of gene regulatory and metabolic networks important for adaptation to low water availability and high-density plantings, which lead to a greater understanding of the physiology underlying these adaptations and 2) we developed technologies to measure important water use efficiency traits and to precisely control gene insertion and replacements events for large scale engineering of pathways in model and target feedstocks.