In planta NAD redox monitoring using a fluorescent protein sensor delivers insight into the in vivo dynamics of plant cytosolic redox metabolism.

Reactive oxygen species and redox markers in plants are measured using a range of chemical probes and biosensors.

Many cell biological and biochemical mechanisms controlling the fundamental process of eukaryotic cell division have been identified; however, the temporal dynamics of biosynthetic processes during the cell division cycle are still elusive. Here, we show that key biosynthetic processes are temporally segregated along the cell cycle. Using budding yeast as a model and single-cell methods to dynamically measure metabolic activity, we observe two peaks in protein synthesis, in the G1 and S/G2/M phase, whereas lipid and polysaccharide synthesis peaks only once, during the S/G2/M phase. Integrating the inferred biosynthetic rates into a thermodynamic-stoichiometric metabolic model, we find that this temporal segregation in biosynthetic processes causes flux changes in primary metabolism, with an acceleration of glucose-uptake flux in G1 and phase-shifted oscillations of oxygen and carbon dioxide exchanges. Through experimental validation of the model predictions, we demonstrate that primary metabolism oscillates with cell-cycle periodicity to satisfy the changing demands of biosynthetic processes exhibiting unexpected dynamics during the cell cycle.

The direct reduction of CO₂ into one-carbon molecules is key to highly efficient biological CO₂-fixation. However, this strategy is currently restricted to anaerobic organisms and low redox potentials. In this study, we introduce the CORE cycle, a synthetic metabolic pathway that converts CO₂ to formate at aerobic conditions and ambient CO₂ levels, using only NADPH as a reductant. Combining theoretical pathway design and analysis, enzyme bioprospecting and high-throughput screening, modular assembly and adaptive laboratory evolution, we realize the CORE cycle in vivo and demonstrate that the cycle supports growth of E. coli by supplementing C1-metabolism and serine biosynthesis from CO₂. We further analyze the theoretical potential of the CORE cycle as a new entry-point for carbon in photorespiration and autotrophy. Overall, our work expands the solution space for biological carbon reduction, offering a promising approach to enhance CO₂ fixation processes such as photosynthesis, and opening avenues for synthetic autotrophy.

Photorespiration causes a substantial decrease in crop yield because of mitochondrial decarboxylation. Alternative pathways (APs) have been designed to relocate the decarboxylation step or even fix additional carbon. To improve the success of transferring those engineered APs from model species to crops, we must understand how they will interact with metabolism and how plant physiology affects their performance. Here, we used multiple mathematical modeling techniques to analyze and compare existing AP designs. We show that carbon-fixing APs are the most promising candidates to replace native photorespiration in major crop species. Our results demonstrate the different metabolic routes that APs use to increase yield and which plant physiology can profit the most from them. We anticipate our results to guide the design of new APs and to help improve existing ones.