Yang Miao, Xie Xi, Kong Fan-Tao, Xie Kun-Peng, Yu Si-Hui, Ma Jing-Yi, Xue Song, Gong Zheng
Key Laboratory of Plant Biotechnology of Liaoning Province, School of Life Sciences, Liaoning Normal University, Dalian, China.
Dalian Key Laboratory of Marine Bioactive Polypeptide Drugs, School of Life Sciences, Liaoning Normal University, Dalian, China.
Front Plant Sci. 2022 May 6;13:860966. doi: 10.3389/fpls.2022.860966. eCollection 2022.
Carbon source serves as a crucial factor for microalgal lipid biosynthesis. The supplied exogenous inorganic or organic carbon affects lipid accumulation in microalgae under stress conditions. However, the impacts of different carbon availability on glycerolipid metabolism, triacylglycerol (TAG) metabolism in particular, still remain elusive in microalgae. starchless mutant BAFJ5 has emerged as a model system to study TAG metabolism, due to its property of hyper-accumulating TAG. In this study, the glycerolipidomic response of the starchless BAFJ5 to high light and nitrogen-deprived (HL-N) stress was deciphered in detail to distinguish glycerolipid metabolism under three carbon supply regimes. The results revealed that the autotrophically and mixotrophically grown BAFJ5 cells aerated with air containing 2% CO presented similar changes in growth, photosynthetic activity, biochemical components, and glycerolipid metabolism under HL-N conditions. But the mixotrophically grown BAFJ5 aerated with air containing 0.04% CO exhibited more superior accumulation in TAG, which was esterified with a significantly higher proportion of C18:1n9 and prominently the lower proportions of polyunsaturated fatty acids. In addition, these cells increased the relative levels of C18:2n6 in the membrane lipids, i.e., monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), in priority, and decreased that of C18:3n3 and C18:4n3 in the betaine lipid, ,,-trimethylhomoserine diacylglycerol (DGTS), subsequently, to adapt to the HL-N stress conditions, compared to the cells under the other two conditions. Thus, it was suggested that . starchless mutant appeared to present distinct metabolism for TAG biosynthesis involving membrane lipid remodeling under distinct carbon supply regimes. This study provides insights into how the different carbon supply regimes affect lipid metabolism in Chlamydomonas starchless cells, which will benefit the optimized production of storage lipids in microalgae.
碳源是微藻脂质生物合成的关键因素。在胁迫条件下，所供应的外源无机或有机碳会影响微藻中的脂质积累。然而，不同碳可用性对甘油脂质代谢，尤其是三酰甘油（TAG）代谢的影响，在微藻中仍不清楚。无淀粉突变体BAFJ5因其超积累TAG的特性，已成为研究TAG代谢的模型系统。在本研究中，详细解析了无淀粉BAFJ5在高光和缺氮（HL-N）胁迫下的甘油脂质组学反应，以区分三种碳供应模式下的甘油脂质代谢。结果表明，在HL-N条件下，以含2% CO的空气通气的自养和混合营养生长的BAFJ5细胞在生长、光合活性、生化成分和甘油脂质代谢方面呈现相似的变化。但以含0.04% CO的空气通气的混合营养生长的BAFJ5在TAG积累方面表现更优，其TAG酯化的C18:1n9比例显著更高，多不饱和脂肪酸比例显著更低。此外，与其他两种条件下的细胞相比，这些细胞优先提高了膜脂中C18:2n6的相对水平，即单半乳糖基二酰甘油（MGDG）和双半乳糖基二酰甘油（DGDG），随后降低了甜菜碱脂中C18:3n3和C18:4n3的相对水平，即，，，-三甲基高丝氨酸二酰甘油（DGTS），以适应HL-N胁迫条件。因此，有人认为无淀粉突变体在不同的碳供应模式下，似乎呈现出涉及膜脂重塑的TAG生物合成的不同代谢。本研究为不同碳供应模式如何影响衣藻无淀粉细胞中的脂质代谢提供了见解，这将有利于微藻中储存脂质的优化生产。
