School of Marine Sciences, Ningbo University, Ningbo, 315832, China.
College of Food and Pharmaceutical Sciences, Ningbo University, Ningbo, 315832, China.
Appl Microbiol Biotechnol. 2020 Mar;104(6):2731-2743. doi: 10.1007/s00253-020-10411-7. Epub 2020 Jan 31.
There are a large number of valuable substances in diatoms, such as neutral lipid and pigments. However, due to the lack of clear metabolic pathways, their applications are still limited. Recently, chemical modulators are found to be powerful tools to investigate the metabolic pathways of neutral lipids. Thus, in this study, to identify new neutral lipid accumulation effectors, we screened the natural products that we separated before in the model diatom Phaeodactylum tricornutum (P. tricornutum) by using Nile-red staining method. Two compounds, penicillide and verrucarin J which were isolated from two marine fungal strains, were identified to promote neutral lipid accumulation. However, penicillide and verrucarin J were also found to significantly inhibit the growth of P. tricornutum through specifically inhibiting the photosynthesis of P. tricornutum. Quantitative analysis results showed that penicillide and verrucarin J significantly increased total lipid and triacylglycerol (TAG) contents, which are consistent with previous Nile-red staining results. The expression of key genes such as DGAT2D, GPAT2, LPAT2, and PAP involved in TAG synthesis and unsaturated fatty acids also increased after penicillide and verrucarin J treatments. Besides, many TAG-rich plastoglobuli formed in plastids shown by increased lipid droplets in the cytosol. Finally, penicillide and verrucarin J were found to reduce the expression of synthetic genes of fucoxanthin, and consequently reduced the content of fucoxanthin, indicating that there might be crosstalk between lipid metabolism and fucoxanthin metabolism. Thus, our work exhibits two useful compounds that could be used to further study the metabolic pathways of neutral lipid and fucoxanthin, which will fulfill the promise of diatoms as low cost, high value, sustainable feedstock for high-value products such as neutral lipid and pigments.
硅藻中含有大量有价值的物质，如中性脂质和色素。然而，由于缺乏明确的代谢途径，它们的应用仍然有限。最近，化学调节剂被发现是研究中性脂质代谢途径的有力工具。因此，在这项研究中，为了鉴定新的中性脂质积累效应物，我们使用尼罗红染色法筛选了我们以前在模式硅藻三角褐指藻（Phaeodactylum tricornutum）中分离的天然产物。从两种海洋真菌菌株中分离得到的两种化合物，penicillide 和 verrucarin J，被鉴定为促进中性脂质积累。然而，penicillide 和 verrucarin J 也被发现通过特异性抑制三角褐指藻的光合作用，显著抑制三角褐指藻的生长。定量分析结果表明，penicillide 和 verrucarin J 显著增加了总脂质和三酰基甘油（TAG）的含量，这与之前的尼罗红染色结果一致。参与 TAG 合成和不饱和脂肪酸的关键基因如 DGAT2D、GPAT2、LPAT2 和 PAP 的表达在 penicillide 和 verrucarin J 处理后也增加了。此外，许多富含 TAG 的质体小球在细胞质中增加的脂滴的作用下在质体中形成。最后，penicillide 和 verrucarin J 被发现降低了 fucoxanthin 合成基因的表达，从而降低了 fucoxanthin 的含量，表明脂质代谢和 fucoxanthin 代谢之间可能存在串扰。因此，我们的工作展示了两种有用的化合物，可用于进一步研究中性脂质和 fucoxanthin 的代谢途径，这将实现硅藻作为低成本、高价值、可持续的生物燃料生产高价值产品（如中性脂质和色素）的承诺。
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