Kondo Mimari, Aoki Motohide, Hirai Kazuho, Ito Ryo, Tsuzuki Mikio, Sato Norihiro
School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan.
Microorganisms. 2023 Apr 30;11(5):1177. doi: 10.3390/microorganisms11051177.
Eukaryotic photosynthetic organisms synthesize triacylglycerols, which are crucial physiologically as major carbon and energy storage compounds and commercially as food oils and raw materials for carbon-neutral biofuel production. TLC analysis has revealed triacylglycerols are present in several cyanobacteria. However, mass spectrometric analysis has shown that freshwater cyanobacterium, sp. PCC 6803, contains plastoquinone-B and acyl plastoquinol with triacylglycerol-like TLC mobility, concomitantly with the absence of triacylglycerol. contains , which is responsible for the bifunctional synthesis of plastoquinone-B and acyl plastoquinol and also for NaCl-stress acclimatizing cell growth. However, information is limited on the taxonomical distribution of these plastoquinone lipids, and their synthesis genes and physiological roles in cyanobacteria. In this study, a euryhaline cyanobacterium, sp. PCC 7002, shows the same plastoquinone lipids as those in , although the levels are much lower than in , triacylglycerol being absent. Furthermore, through an analysis of a disruptant to the homolog of in , it is found that the homolog in , similar to in , contributes bifunctionally to the synthesis of plastoquinone-B and acyl plastoquinol; however, the extent of the contribution of the homolog gene to NaCl acclimatization is smaller than that of in . These observations suggest strain- or ecoregion-dependent development of the physiological roles of plastoquinone lipids in cyanobacteria and show the necessity to re-evaluate previously identified cyanobacterial triacylglycerol through TLC analysis with mass spectrometric techniques.
真核光合生物合成三酰甘油，三酰甘油作为主要的碳和能量储存化合物在生理上至关重要，在商业上作为食用油和碳中性生物燃料生产的原料。薄层色谱分析表明，几种蓝细菌中存在三酰甘油。然而，质谱分析表明，淡水蓝细菌集胞藻属PCC 6803含有质体醌-B和具有类似三酰甘油薄层色谱迁移率的酰基质体氢醌，同时不存在三酰甘油。集胞藻属PCC 6803含有PqsA，它负责质体醌-B和酰基质体氢醌的双功能合成，也负责细胞在NaCl胁迫下的适应性生长。然而，关于这些质体醌脂质在蓝细菌中的分类分布、它们的合成基因及其生理作用的信息有限。在本研究中，一种广盐性蓝细菌嗜盐集胞藻PCC 7002显示出与集胞藻属PCC 6803相同的质体醌脂质，尽管其含量远低于集胞藻属PCC 6803，且不存在三酰甘油。此外，通过对嗜盐集胞藻PCC 7002中PqsA同源物的缺失突变体进行分析，发现嗜盐集胞藻PCC 7002中的PqsA同源物与集胞藻属PCC 6803中的PqsA类似，对质体醌-B和酰基质体氢醌的合成具有双功能作用；然而，该同源基因对NaCl适应性的贡献程度小于集胞藻属PCC 6803中的PqsA。这些观察结果表明，质体醌脂质在蓝细菌中的生理作用存在菌株或生态区域依赖性发展，并表明有必要通过质谱技术的薄层色谱分析重新评估先前鉴定的蓝细菌三酰甘油。
