Colin Ratledge Center for Microbial Lipids, School of Agricultural Engineering and Food Science, Shandong University of Technology, 255000, Zibo, Shandong, China.
Department of Biology, South Texas Center of Emerging Infectious Diseases (STCEID), University of Texas, 78249, San Antonio, TX, USA.
Microb Cell Fact. 2021 Feb 27;20(1):52. doi: 10.1186/s12934-021-01545-y.
Mucor circinelloides WJ11 is a high-lipid producing strain and an excellent producer of γ-linolenic acid (GLA) which is crucial for human health. We have previously identified genes that encode for AMP-activated protein kinase (AMPK) complex in M. circinelloides which is an important regulator for lipid accumulation. Comparative transcriptional analysis between the high and low lipid-producing strains of M. circinelloides showed a direct correlation in the transcriptional level of AMPK genes with lipid metabolism. Thus, the role of Snf-β, which encodes for β subunit of AMPK complex, in lipid accumulation of the WJ11 strain was evaluated in the present study.
The results showed that lipid content of cell dry weight in Snf-β knockout strain was increased by 32 % (from 19 to 25 %). However, in Snf-β overexpressing strain, lipid content of cell dry weight was decreased about 25 % (from 19 to 14.2 %) compared to the control strain. Total fatty acid analysis revealed that the expression of the Snf-β gene did not significantly affect the fatty acid composition of the strains. However, GLA content in biomass was increased from 2.5 % in control strain to 3.3 % in Snf-β knockout strain due to increased lipid accumulation and decreased to 1.83 % in Snf-β overexpressing strain. AMPK is known to inactivate acetyl-CoA carboxylase (ACC) which catalyzes the rate-limiting step in lipid synthesis. Snf-β manipulation also altered the expression level of the ACC1 gene which may indicate that Snf-β control lipid metabolism by regulating ACC1 gene.
Our results suggested that Snf-β gene plays an important role in regulating lipid accumulation in M. circinelloides WJ11. Moreover, it will be interesting to evaluate the potential of other key subunits of AMPK related to lipid metabolism. Better insight can show us the way to manipulate these subunits effectively for upscaling the lipid production. Up to our knowledge, it is the first study to investigate the role of Snf-β in lipid accumulation in M. circinelloides.
卷枝毛霉（Mucor circinelloides）WJ11 是一株产高油脂的菌株，也是 γ-亚麻酸（GLA）的优秀生产者，GLA 对人类健康至关重要。我们之前已经鉴定出卷枝毛霉中编码 AMP 激活蛋白激酶（AMPK）复合物的基因，该复合物是脂质积累的重要调节剂。对产高油脂和低油脂卷枝毛霉菌株的比较转录分析表明，AMPK 基因的转录水平与脂质代谢呈直接相关性。因此，本研究评估了编码 AMPK 复合物 β 亚基的 Snf-β 在 WJ11 菌株脂质积累中的作用。
结果表明，Snf-β 敲除菌株的细胞干重的油脂含量增加了 32%（从 19%增加到 25%）。然而，在 Snf-β 过表达菌株中，细胞干重的油脂含量比对照菌株减少了约 25%（从 19%减少到 14.2%）。总脂肪酸分析表明，Snf-β 基因的表达并未显著影响菌株的脂肪酸组成。然而，由于脂质积累增加，GLA 含量从对照菌株的 2.5%增加到 Snf-β 敲除菌株的 3.3%，而在 Snf-β 过表达菌株中则降低到 1.83%。AMPK 已知可使乙酰辅酶 A 羧化酶（ACC）失活，而 ACC 催化脂质合成的限速步骤。Snf-β 的操作也改变了 ACC1 基因的表达水平，这表明 Snf-β 通过调节 ACC1 基因来控制脂质代谢。
我们的结果表明，Snf-β 基因在调节卷枝毛霉 WJ11 的脂质积累中起着重要作用。此外，评估与脂质代谢相关的 AMPK 的其他关键亚基的潜力将是有趣的。更好的认识可以为我们提供有效操纵这些亚基以扩大脂质生产的方法。据我们所知，这是第一项研究 Snf-β 在卷枝毛霉脂质积累中的作用的研究。
