Australian Institute for Bioengineering and Nanotechnology, School of Chemical Engineering, University of Queensland, Brisbane, Queensland 4072, Australia.
School of Mathematics and Statistics, The University of Sydney, New South Wales 2006, Australia.
Plant Sci. 2018 Aug;273:50-60. doi: 10.1016/j.plantsci.2018.03.027. Epub 2018 Apr 5.
The compartmentalization of C plants increases photosynthetic efficiency, while constraining how material and energy must flow in leaf tissues. To capture this metabolic phenomenon, a generic plant metabolic reconstruction was replicated into four connected spatiotemporal compartments, namely bundle sheath (B) and mesophyll (M) across the day and night cycle. The C leaf model was used to explore how amenable polyhydroxybutyrate (PHB) production is with these four compartments working cooperatively. A strategic pattern of metabolite conversion and exchange emerged from a systems-level network that has very few constraints imposed; mainly the sequential two-step carbon capture in mesophyll, then bundle sheath and photosynthesis during the day only. The building of starch reserves during the day and their mobilization during the night connects day and night metabolism. Flux simulations revealed that PHB production did not require rerouting of metabolic pathways beyond what is already utilised for growth. PHB yield was sensitive to photoassimilation capacity, availability of carbon reserves, ATP maintenance, relative photosynthetic activity of B and M, and type of metabolites exchanged in the plasmodesmata, but not sensitive towards compartmentalization. Hence, the compartmentalization issues currently encountered are likely to be kinetic or thermodynamic limitations rather than stoichiometric.
C 植物的隔室化提高了光合作用效率，同时限制了物质和能量在叶片组织中的流动方式。为了捕捉这一代谢现象，将通用植物代谢重建复制到四个连接的时空隔室中，即白天和黑夜的束鞘（B）和叶肉（M）。使用 C 叶模型来探索多羟基丁酸酯（PHB）生产在这四个隔室协同工作时的可行性。从系统层面的网络中出现了一种战略代谢物转化和交换模式，其中几乎没有施加任何约束；主要是在白天仅进行光合作用时，叶肉中进行顺序的两步碳捕获，然后是束鞘。白天储存淀粉储备，晚上动员它们，连接白天和黑夜的代谢。通量模拟表明，PHB 生产不需要重新路由代谢途径，超出了已经用于生长的途径。PHB 产量对光同化能力、碳储备的可用性、ATP 维持、B 和 M 的相对光合作用活性以及质膜通道中交换的代谢物类型敏感，但对隔室化不敏感。因此，目前遇到的隔室化问题可能是动力学或热力学限制，而不是化学计量限制。
