State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; Joint International Research Laboratory of Metabolic and Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China; Biomass Energy Research Center, Shanghai Jiao Tong University, Shanghai 200240, China.
Instrumental Analysis Center, Shanghai Jiao Tong University, Shanghai 200240, China.
Biochim Biophys Acta Mol Cell Biol Lipids. 2019 Dec;1864(12):158522. doi: 10.1016/j.bbalip.2019.158522. Epub 2019 Sep 2.
Organisms use various adaptive strategies against phosphate stress, including lipid remodeling. Here, the response of major membrane lipids to phosphate stress was analyzed in Synechococcus sp. PCC 7942. Unlike plants and eukaryotic microalgae, no significant increases in neutral lipids were found, whereas glycolipids content increased to as high as 6.13% (of dry cell weight, DCW) and phospholipids decreased to 0.34% (of DCW) after 16 days of cultivation without phosphate. Glycolipids accumulation were mainly attributed to the significant increase of digalactosyldiacylglycerol (DGDG) by 50% and sulfoquinovosyldiaclglycerol (SQDG) by 90%, both of which acted as complementary lipids for phosphatidylglycerol (PG) in the cyanobacterial membrane. Also, a notable increase in content (by 48%) of C18 fatty acids (especially C18:1) was observed in all glycolipids at the expense of C12 and C14 (72%). These changes may contribute to membrane fluidity and photosynthetic activity for basic cell metabolism and phosphate stress adaptation. Lipidomic analyses showed the reduction of PG 18:1/16: 0 (by 52%) with the increase of DGDG 18:1/16:0 (133%) and SQDG 18:1/16:0 (245%), strongly suggesting a direct conversion of PG to DGDG and SQDG. Moreover, the decreasing amount of monogalactosyldiacylglycerol (MGDG) 16:1/16:0 (22%) was consistent with the increase of free fatty acids (125%) on day 2 of phosphate absence, which suggested that MGDG is more likely to provide a pool of fatty acids for de novo synthesis of glycolipids. This study provides valuable insight into cyanobacteria adaptation strategies to phosphate stress by membrane lipid remodeling and unveils the underlying acyl chain fluxes into glycolipids.
生物利用各种适应性策略来应对磷酸盐胁迫，包括脂类重塑。在这里，分析了磷酸盐胁迫下聚球藻 PCC 7942 主要膜脂的响应。与植物和真核微藻不同，在没有磷酸盐的情况下培养 16 天后，并未发现中性脂质显著增加，而糖脂含量增加到高达 6.13%（干重，DCW），磷脂减少到 0.34%（DCW）。糖脂的积累主要归因于二半乳糖基二酰基甘油（DGDG）显著增加 50%和硫酸奎诺糖基二酰基甘油（SQDG）增加 90%，两者都作为蓝细菌膜中磷脂酰甘油（PG）的补充脂质。此外，所有糖脂中的 C18 脂肪酸（特别是 C18:1）含量显著增加（增加 48%），而 C12 和 C14（72%）则减少。这些变化可能有助于膜流动性和光合作用活性，以维持基本细胞代谢和适应磷酸盐胁迫。脂质组学分析表明，PG 18:1/16:0（减少 52%）减少，而 DGDG 18:1/16:0（增加 133%）和 SQDG 18:1/16:0（增加 245%）增加，强烈表明 PG 直接转化为 DGDG 和 SQDG。此外，在没有磷酸盐的第 2 天，单半乳糖基二酰基甘油（MGDG）16:1/16:0（减少 22%）的减少量与游离脂肪酸（增加 125%）的增加量一致，这表明 MGDG 更有可能为糖脂的从头合成提供脂肪酸池。本研究通过膜脂重塑提供了对蓝细菌适应磷酸盐胁迫的策略的有价值的见解，并揭示了酰链通量到糖脂的潜在机制。
