Nitrogen deprivation is known to improve lipid accumulation in microalgae and thraustochytrids. However, the patterns of fatty acid production and the molecular mechanisms underlying the accumulation of unsaturated and saturated fatty acids (SFAs) under nitrogen starvation remain largely unknown for thraustochytrids. In this study, batch culture experiments under nitrogen replete and nitrogen starvation conditions were performed, and the changes in the transcriptome of Aurantiochytrium sp. PKU#SW8 strain between these conditions were investigated. Our results showed improved yields of total fatty acids (TFAs), total unsaturated fatty acids, and total SFAs under nitrogen starvation, which suggested that nitrogen starvation favors the accumulation of both unsaturated and saturated fatty acids in PKU#SW8. However, nitrogen starvation resulted in a more than 2.36-fold increase of SFAs whereas a 1.7-fold increase of unsaturated fatty acids was observed, indicating a disproportionate increase in these groups of fatty acids. The fabD and enoyl-CoA hydratase genes were significantly upregulated under nitrogen starvation, supporting the observed increase in the yield of TFAs from 2.63 ± 0.22 g/L to 3.64 ± 0.16 g/L. Furthermore, the pfaB gene involved in the polyketide synthase (PKS) pathway was significantly upregulated under nitrogen starvation. This suggested that the increased expression of the pfaB gene under nitrogen starvation may be one of the explanations for the increased yield of docosahexaenoic acid by 1.58-fold. Overall, our study advances the current understanding of the molecular mechanisms that underlie the response of thraustochytrids to nitrogen deprivation and their fatty acid biosynthesis.

中文翻译：

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氮饥饿会增强 Aurantiochytrium sp. 中饱和和不饱和脂肪酸的产生。PKU#SW8 通过调节关键生物合成基因

已知氮剥夺可改善微藻和破囊壶菌中的脂质积累。然而，对于破囊壶菌来说，脂肪酸产生的模式和在氮饥饿下不饱和和饱和脂肪酸 (SFA) 积累的分子机制在很大程度上仍然是未知的。本研究进行了氮充足和氮饥饿条件下的分批培养实验，研究了金壶菌转录组的变化。sp。研究了这些条件之间的 PKU#SW8 菌株。我们的结果表明，在氮饥饿条件下，总脂肪酸 (TFA)、总不饱和脂肪酸和总 SFA 的产量有所提高，这表明氮饥饿有利于 PKU#SW8 中不饱和和饱和脂肪酸的积累。然而，氮饥饿导致 SFA 增加超过 2.36 倍，而观察到不饱和脂肪酸增加 1.7 倍，表明这些脂肪酸组的增加不成比例。fabD 和烯酰辅酶A 水合酶基因在氮饥饿下显着上调，支持观察到的 TFA 产量从 2.63 ± 0.22 g/L 增加到 3.64 ± 0.16 g/L。此外，pfa在氮饥饿条件下，参与聚酮化合物合酶 (PKS) 途径的 B 基因显着上调。这表明在氮饥饿条件下pfa B 基因的表达增加可能是二十二碳六烯酸产量增加 1.58 倍的原因之一。总体而言，我们的研究推进了目前对破囊壶菌对氮剥夺及其脂肪酸生物合成反应的分子机制的理解。