Reimport of carbon from cytosolic and vacuolar sugar pools into the Calvin-Benson cycle explains photosynthesis labeling anomalies.
Reimport of carbon from cytosolic and vacuolar sugar pools into the Calvin-Benson cycle explains photosynthesis labeling anomalies.
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DOI：
10.1073/pnas.2121531119
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发表时间：
2022-03-15
影响因子：
11.1
通讯作者：
Sharkey TD
中科院分区：
文献类型：
--
作者：
Xu Y;Wieloch T;Kaste JAM;Shachar-Hill Y;Sharkey TD
当13CO2喂入叶片时，光合作用代谢物很快就会被标记，但标记的时间进程揭示了光合作用代谢动力学中涉及的额外贡献过程。证明了三个这样的过程的存在，并开发了一个代谢流量模型来探索和表征它们。该模型与碳从胞浆和空泡糖通过磷酸戊糖氧化途径缓慢返回到Calvin-Benson循环中是一致的。我们的结果为碳同化如何整合到光合作用细胞的代谢网络中提供了洞察力，并对全球碳通量产生了影响。当碳的同位素被提供给光合作用的叶片时，Calvin-Benson循环(CBC)的代谢物最初被快速标记，但随后标记的速度大大减慢，这引发了关于CBC在叶片代谢中的整合的问题。我们利用茶树叶代谢物标记的2小时时间过程来测试当二氧化碳源快速切换到13CO2时12C洗脱的模型。将指数函数拟合到CBC代谢物的时间进程中，我们发现了三个时间上不同的过程对标记做出贡献的证据，但没有证据表明代谢不活跃的池。接下来，我们通过13C同位素非平稳代谢通量分析对所有代谢物的数据进行建模，测试了各种通量网络。在最能解释测量数据的模型中，有三个过程决定了CBC代谢物的标记。第一种是固定进入的13CO2；第二种是胞浆葡萄糖中的弱标记碳在氧化戊糖磷酸途径反应后重新进入CBC，这形成了绕过CBC大部分的分流。第三，液泡中标记很弱的碳进一步稀释了标记。这个模型预测分流大约是净固定二氧化碳速率的5%，并解释了标记的三个阶段。在显示三个隔室的相互连接时，我们已经描绘了更完整的碳如何通过光合作用代谢的图景，其方式将CBC、胞质糖池、葡萄糖-6-磷酸分流和液泡糖整合到一个系统中。
Photosynthesis metabolites are quickly labeled when 13CO2 is fed to leaves, but the time course of labeling reveals additional contributing processes involved in the metabolic dynamics of photosynthesis. The existence of three such processes is demonstrated, and a metabolic flux model is developed to explore and characterize them. The model is consistent with a slow return of carbon from cytosolic and vacuolar sugars into the Calvin–Benson cycle through the oxidative pentose phosphate pathway. Our results provide insight into how carbon assimilation is integrated into the metabolic network of photosynthetic cells with implications for global carbon fluxes. When isotopes of carbon are fed to photosynthesizing leaves, metabolites of the Calvin–Benson cycle (CBC) are rapidly labeled initially, but then the rate of labeling slows considerably, raising questions about the integration of the CBC within leaf metabolism. We have used 2-h time courses of labeling of Camelina sativa leaf metabolites to test models of 12C washout when the CO2 source is rapidly switched to 13CO2. Fitting exponential functions to the time course of CBC metabolites, we found evidence for three temporally distinct processes contributing to the labeling but none for metabolically inactive pools. We next modeled the data of all metabolites by 13C isotopically nonstationary metabolic flux analysis, testing a variety of flux networks. In the model that best explains measured data, three processes determine CBC metabolite labeling. First is fixation of incoming 13CO2; second is dilution by weakly labeled carbon in cytosolic glucose reentering the CBC following oxidative pentose phosphate pathway reactions, which forms a shunt bypassing much of the CBC. Third, very weakly labeled carbon from the vacuole further dilutes the labeling. This model predicts the shunt proceeds at about 5% of the rate of net CO2 fixation and explains the three phases of labeling. In showing the interconnection of three compartments, we have drawn a more complete picture of how carbon moves through photosynthetic metabolism in a way that integrates the CBC, cytosolic sugar pools, glucose-6-phosphate shunt, and vacuolar sugars into a single system.
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影响因子：
5.6
作者：
Hilgers EJA;Schöttler MA;Mettler-Altmann T;Krueger S;Dörmann P;Eicks M;Flügge UI;Häusler RE
通讯作者：
Häusler RE
影响因子：
3.8
作者：
Hendry, John I.;Prasannan, Charulata;Wangikar, Pramod P.
通讯作者：
Wangikar, Pramod P.
影响因子：
6.1
作者：
DUNNE, A
通讯作者：
DUNNE, A
影响因子：
7.4
作者：
Eicks, M;Maurino, V;Fischer, K
通讯作者：
Fischer, K
影响因子：
6.9
作者：
Arrivault S;Obata T;Szecówka M;Mengin V;Guenther M;Hoehne M;Fernie AR;Stitt M
通讯作者：
Stitt M