Carbohydrate Metabolism and the Trehalose Biosynthetic Pathway in Maize Kernels Grown \u3ci\u3eIn Vitro\u3c/i\u3e under Sucrose Starvation Stress

Drought is an increasing issue that many farmers encounter especially in hot arid climates with little rainfall. High temperatures and inadequate rainfall at certain stages in crop development can have disastrous consequences to yield. In maize, drought occurring near or during the flowering stage often causes significant kernel abortion that greatly impacts potential yield. The trehalose biosynthetic pathway has recently been found to be important in plant metabolism in response to stress in higher order plants. Trehalose is currently known throughout the plant and animal kingdoms as an osmoprotectant, high energy fuel source, structural component, and involved in pathogen response. New insight on the role of the trehalose pathway focuses on the sugar phosphate intermediate trehalose-6-phosphate (Tre6P) and its regulatory role on the Sucrose non-fermenting Related Kinase 1 (SnRK1). SnRK1 has been shown to be a central regulator of numerous catabolic and anabolic events critical to plant metabolism. Slight changes in trace Tre6P levels within the plant often cause dramatic phenotypes suggesting that Tre6P is acting as a metabolic switch in response to carbon availability. Understanding the role of the trehalose and SnRK1 pathways in higher plant species such as maize will provide a better understanding of carbon partitioning in plants especially as it pertains to kernel abortion and potentially increasing yields. This study first explores the practicality of in vitro kernel culture as a means to evaluate sink strength in the context of regulation by Tre6P and the SnRK1 pathway on maize inbred B73, a Nested Association Mapping (NAM) population parent line, and the model organism for this study. Sink strength is then characterized for 14 additional NAM inbred parent lines as well as a more detailed analysis of Tre6P and SnRK1 involvement for selected inbred lines Oh43 and M37W. The findings of this study greatly support the involvement of the SnRK1 pathway in response to sucrose starvation stress and its regulation by Tre6P. Advisor: Mark Lagrimin