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首页> 外文期刊>BMC Biotechnology >Oil accumulation in the model green alga Chlamydomonas reinhardtii : characterization, variability between common laboratory strains and relationship with starch reserves
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Oil accumulation in the model green alga Chlamydomonas reinhardtii : characterization, variability between common laboratory strains and relationship with starch reserves

机译：绿藻莱茵衣藻模型中的油积累：表征，常见实验室菌株之间的变异性以及与淀粉储量的关系

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Background When cultivated under stress conditions, many microalgae species accumulate both starch and oil (triacylglycerols). The model green microalga Chlamydomonas reinhardtii has recently emerged as a model to test genetic engineering or cultivation strategies aiming at increasing lipid yields for biodiesel production. Blocking starch synthesis has been suggested as a way to boost oil accumulation. Here, we characterize the triacylglycerol (TAG) accumulation process in Chlamydomonas and quantify TAGs in various wild-type and starchless strains. Results In response to nitrogen deficiency, Chlamydomonas reinhardtii produced TAGs enriched in palmitic, oleic and linoleic acids that accumulated in oil-bodies. Oil synthesis was maximal between 2 and 3 days following nitrogen depletion and reached a plateau around day 5. In the first 48 hours of oil deposition, a ~80% reduction in the major plastidial membrane lipids occurred. Upon nitrogen re-supply, mobilization of TAGs started after starch degradation but was completed within 24 hours. Comparison of oil content in five common laboratory strains (CC124, CC125, cw15 , CC1690 and 11-32A) revealed a high variability, from 2 μg TAG per million cell in CC124 to 11 μg in 11-32A. Quantification of TAGs on a cell basis in three mutants affected in starch synthesis ( cw15sta1-2, cw15sta6 and cw15sta7-1 ) showed that blocking starch synthesis did not result in TAG over-accumulation compared to their direct progenitor, the arginine auxotroph strain 330 . Moreover, no significant correlation was found between cellular oil and starch levels among the twenty wild-type, mutants and complemented strains tested. By contrast, cellular oil content was found to increase steeply with salt concentration in the growth medium. At 100 mM NaCl, oil level similar to nitrogen depletion conditions could be reached in CC124 strain. Conclusion A reference basis for future genetic studies of oil metabolism in Chlamydomonas is provided. Results highlight the importance of using direct progenitors as control strains when assessing the effect of mutations on oil content. They also suggest the existence in Chlamydomonas of complex interplays between oil synthesis, genetic background and stress conditions. Optimization of such interactions is an alternative to targeted metabolic engineering strategies in the search for high oil yields.
机译：背景技术在压力条件下种植时，许多微藻种会同时积累淀粉和油（三酰基甘油）。绿色微藻莱茵衣藻模型最近已成为测试基因工程或栽培策略的模型，旨在提高生物柴油生产的脂质产量。已经提出了阻止淀粉合成作为增加油积累的方法。在这里，我们表征衣藻中的三酰基甘油（TAG）积累过程，并量化各种野生型和无淀粉菌株中的TAG。结果响应于氮缺乏，莱茵衣藻产生了富含棕榈酸，油酸和亚油酸的TAG，这些TAG积累在油体中。氮消耗后的2至3天，油的合成达到最大，并在第5天左右达到平稳。在油沉积的前48小时中，主要的质膜脂质减少了约80％。再次供氮后，淀粉降解后，TAGs的动员开始，但在24小时内完成。比较五种常见实验室菌株（CC124，CC125，cw15，CC1690和11-32A）中的油含量，发现变异性很高，从CC124中每百万个细胞2μgTAG到11-32A中11μg。在细胞中对受淀粉合成影响的三个突变体（cw15sta1-2，cw15sta6和cw15sta7-1）中TAG的定量分析表明，与其直接祖先精氨酸营养缺陷型菌株330相比，阻断淀粉合成不会导致TAG的过度积累。而且，在所测试的二十种野生型，突变体和互补菌株中，细胞油和淀粉水平之间没有发现显着相关性。相反，发现细胞中的油含量随着生长培养基中盐浓度的增加而急剧增加。在100 mM NaCl中，CC124菌株可达到类似于氮耗竭条件的油位。结论为衣藻油代谢的遗传研究提供了参考依据。结果突出了评估突变对含油量的影响时使用直接祖细胞作为对照菌株的重要性。他们还表明衣藻中存在油的合成，遗传背景和胁迫条件之间复杂的相互作用。这种相互作用的优化是寻找高油收率时靶向代谢工程策略的替代方法。

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