(165g) A Maize Metabolic Atlas Revealed Bottlenecks in Temperature Stress Conditions

Global warming is a major concern of the 21st century. The productivity of maize, one of the most important staple cereal crops, has been severely impacted by global warming. Although the impact of temperature stress on individual plant tissues has been explored in a limited capacity, a holistic understanding of the interactive metabolism between different plant tissues under temperature stress is still at its infancy. To address this, we reconstructed the first ever multi-tissue genome-scale metabolic model (iZMA6517) of maize, consisting of individual root, shoot, seed, and leaf models connected through vascular tissues. The model has 6,517 genes, 20,238 reactions (5,228 unique), and 19,854 metabolites (5,026 unique). We incorporated heat and cold stress-related transcriptomics data with the iZMA6517 through a novel Transcript Distributed (TD)E-flux algorithm. Furthermore, we developed and implemented a metabolic bottleneck analysis method in which each reaction was assessed for its impact on the growth rate upon expansion of flux space of the iZMA6517, thus postulating metabolic bottlenecks in both heat and cold stress. While only 5 reactions were identified as metabolic bottlenecks in the cold stress, the number was 180 in the heat stress, revealing the fundamental difference of stress responses between these conditions. In the heat stress, 70% of the bottlenecks are from the leaf tissue, whereas root tissue contained 40% of the bottlenecks in the cold stress. In addition, thermodynamic analysis revealed the potential low driving force of bottleneck reactions, identifying the intricate relationship between thermodynamics and temperature stress. Overall, the metabolic bottlenecks identified in this study will work as a guideline to engineer temperature stress-tolerant maize genotypes, thus promoting sustainability in food production.