The Regulation of Photosynthetic Structure and Function during Nitrogen Deprivation in Chlamydomonas reinhardtii
The Regulation of Photosynthetic Structure and Function during Nitrogen Deprivation in Chlamydomonas reinhardtii
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DOI：
10.1104/pp.114.250530
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发表时间：
2015-02-01
期刊：
影响因子：
7.4
通讯作者：
Shachar-Hill, Yair
中科院分区：
文献类型：
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作者：
Juergens, Matthew T.;Deshpande, Rahul R.;Shachar-Hill, Yair
尽管许多单细胞藻类的光合作用器官衰退，但在营养剥夺后，它们仍会积累碳储存化合物。为了了解光合作用在这一具有潜在生物能价值的过程中的调节和作用，我们分析了模型藻莱茵衣藻在缺氮后的光合作用结构和功能。将转录组学、蛋白质组学、代谢物和脂质分析以及微观时程数据与光合功能的多种测量相结合。光系统 I 和 II 以及大多数触角基因的转录物和蛋白质水平以不同的轨迹下降；类囊体膜脂质水平下降，但其比例保持相似，并且类囊体膜组织似乎得以保留。细胞叶绿素 (Chl) 含量在 24 小时内下降超过 2 倍，我们从转录蛋白和 C-13 标记率得出结论，翻译前和翻译后的 Chl 合成均下调，并且 Chl 水平下降是因为合成快速停止和细胞生长稀释，而不是因为降解。光合作用驱动的氧气产生、光系统 II 的效率以及 P700(+) 还原和电致变色动力学均随时间推移而下降，但没有证据表明存在大量能量溢出。结果还表明，在前 24 小时内，线性电子流比循环流下降了约 15%。将卡尔文-本森循环转录物和酶水平与光合 (CO2)-C-13 掺入率的变化进行比较也表明，在诱导高三酰甘油积累率之前，淀粉合成过程中光合通量的多级协调下调。
The accumulation of carbon storage compounds by many unicellular algae after nutrient deprivation occurs despite declines in their photosynthetic apparatus. To understand the regulation and roles of photosynthesis during this potentially bioenergetically valuable process, we analyzed photosynthetic structure and function after nitrogen deprivation in the model alga Chlamydomonas reinhardtii. Transcriptomic, proteomic, metabolite, and lipid profiling and microscopic time course data were combined with multiple measures of photosynthetic function. Levels of transcripts and proteins of photosystems I and II and most antenna genes fell with differing trajectories; thylakoid membrane lipid levels decreased, while their proportions remained similar and thylakoid membrane organization appeared to be preserved. Cellular chlorophyll (Chl) content decreased more than 2-fold within 24 h, and we conclude from transcript protein and C-13 labeling rates that Chl synthesis was down-regulated both pre- and posttranslationally and that Chl levels fell because of a rapid cessation in synthesis and dilution by cellular growth rather than because of degradation. Photosynthetically driven oxygen production and the efficiency of photosystem II as well as P700(+) reduction and electrochromic shift kinetics all decreased over the time course, without evidence of substantial energy overflow. The results also indicate that linear electron flow fell approximately 15% more than cyclic flow over the first 24 h. Comparing Calvin-Benson cycle transcript and enzyme levels with changes in photosynthetic (CO2)-C-13 incorporation rates also pointed to a coordinated multilevel down-regulation of photosynthetic fluxes during starch synthesis before the induction of high triacylglycerol accumulation rates.