Plant central carbon metabolism comprises several important metabolic pathways acting together to support plant growth and yield establishment. Despite the emergence of ¹³C-based dynamic approaches, the regulation of metabolic fluxes between light and dark conditions has not yet received sufficient attention for agronomically relevant plants. Here, we investigated the impact of light/dark conditions on carbon allocation processes within central carbon metabolism of Brassica napus after U-¹³C-glucose incorporation into leaf discs. Leaf gas-exchanges and metabolite contents were weakly impacted by the leaf disc method and the incorporation of glucose. ¹³C-analysis by GC-MS showed that U-¹³C-glucose was converted to fructose for de novo biosynthesis of sucrose at similar rates in both light and dark conditions. However, light conditions led to a reduced commitment of glycolytic carbons towards respiratory substrates (pyruvate, alanine, malate) and TCA cycle intermediates compared to dark conditions. Analysis of ¹³C-enrichment at the isotopologue level and metabolic pathway isotopic tracing reconstructions identified the contribution of multiple pathways to serine biosynthesis in light and dark conditions. However, the direct contribution of the glucose-6-phosphate shunt to serine biosynthesis was not observed. Our results also provided isotopic evidences for an active metabolic connection between the TCA cycle, glycolysis and photorespiration in light conditions through a rapid reallocation of TCA cycle decarboxylations back to the TCA cycle through photorespiration and glycolysis. Altogether, these results suggest the active coordination of core metabolic pathways across multiple compartments to reorganize C-flux modes.

植物中心碳代谢包括几个重要的代谢途径，它们共同作用以支持植物生长和产量建立。尽管出现了基于C的动态方法，但对于农艺相关植物来说，光照和黑暗条件之间代谢通量的调节尚未得到足够的重视。在这里，我们研究了 U- ¹³ C-葡萄糖掺入叶盘后，光/暗条件对甘蓝型油菜中央碳代谢内碳分配过程的影响。叶盘法和葡萄糖掺入对叶气体交换和代谢物含量的影响微弱。 ¹³ GC-MS 分析表明，U- ¹³ C-葡萄糖在光照和黑暗条件下以相似的速率转化为果糖，用于蔗糖的从头生物合成。然而，与黑暗条件相比，光照条件导致糖酵解碳对呼吸底物（丙酮酸、丙氨酸、苹果酸）和 TCA 循环中间体的承诺减少。同位素水平上的 ¹³ C富集分析和代谢途径同位素示踪重建确定了多种途径在光照和黑暗条件下对丝氨酸生物合成的贡献。然而，没有观察到葡萄糖-6-磷酸分流对丝氨酸生物合成的直接贡献。我们的结果还通过光呼吸和糖酵解将 TCA 循环脱羧快速重新分配回 TCA 循环，为光照条件下 TCA 循环、糖酵解和光呼吸之间的活跃代谢联系提供了同位素证据。总而言之，这些结果表明跨多个区室的核心代谢途径的积极协调以重组 C 通量模式。