The Microalgal Biotechnology Laboratory, The French Associates Institute for Agriculture and Biotechnology, Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Sede Boker Campus 84990, Israel.
Toulouse Biotechnology Institute Bio & Chemical Engineering, Institut National de la Recherche Agronomique, Institute National Des Sciences Appliquees, Le Centre national de la recherche scientifique, Toulouse 31077, France.
Plant Physiol. 2024 Jan 31;194(2):958-981. doi: 10.1093/plphys/kiad525.
Diatoms (Bacillariophyceae) accumulate neutral storage lipids in lipid droplets during stress conditions, which can be rapidly degraded and recycled when optimal conditions resume. Since nutrient and light availability fluctuate in marine environments, storage lipid turnover is essential for diatom dominance of marine ecosystems. Diatoms have garnered attention for their potential to provide a sustainable source of omega-3 fatty acids. Several independent proteomic studies of lipid droplets isolated from the model oleaginous pennate diatom Phaeodactylum tricornutum have identified a previously uncharacterized protein with an acyl-CoA binding (ACB) domain, Phatrdraft_48778, here referred to as Phaeodactylum tricornutum acyl-CoA binding protein (PtACBP). We report the phenotypic effects of CRISPR-Cas9 targeted genome editing of PtACBP. ptacbp mutants were defective in lipid droplet and triacylglycerol degradation, as well as lipid and eicosapentaenoic acid synthesis, during recovery from nitrogen starvation. Transcription of genes responsible for peroxisomal β-oxidation, triacylglycerol lipolysis, and eicosapentaenoic acid synthesis was inhibited. A lipid-binding assay using a synthetic ACB domain from PtACBP indicated preferential binding specificity toward certain polar lipids. PtACBP fused to eGFP displayed an endomembrane-like pattern, which surrounded the periphery of lipid droplets. PtACBP is likely responsible for intracellular acyl transport, affecting cell division, development, photosynthesis, and stress response. A deeper understanding of the molecular mechanisms governing storage lipid turnover will be crucial for developing diatoms and other microalgae as biotechnological cell factories.
硅藻（Bacillariophyceae）在胁迫条件下会在脂滴中积累中性储存脂质，当条件恢复最佳时，这些脂质可以迅速降解和再循环。由于海洋环境中营养物质和光照的可用性会波动，因此储存脂质的周转对于硅藻在海洋生态系统中的优势地位至关重要。硅藻因其可能成为ω-3 脂肪酸可持续来源而受到关注。对模式产油金藻（Phaeodactylum tricornutum）分离的脂滴进行的几项独立蛋白质组学研究鉴定出一种以前未被表征的具有酰基辅酶 A 结合（ACB）结构域的蛋白，Phatrdraft_48778，在这里称为金藻酰基辅酶 A 结合蛋白（PtACBP）。我们报告了 CRISPR-Cas9 靶向基因组编辑 PtACBP 的表型效应。ptacbp 突变体在从氮饥饿中恢复时，脂滴和三酰基甘油降解以及脂质和二十碳五烯酸合成缺陷。负责过氧化物酶体β-氧化、三酰基甘油脂解和二十碳五烯酸合成的基因转录受到抑制。使用来自 PtACBP 的合成 ACB 结构域进行的脂质结合测定表明，其对某些极性脂质具有优先的结合特异性。与 eGFP 融合的 PtACBP 显示出类似于内质网的模式，包围在脂滴的外围。PtACBP 可能负责细胞内酰基运输，影响细胞分裂、发育、光合作用和应激反应。深入了解调节储存脂质周转的分子机制对于开发硅藻和其他微藻作为生物技术细胞工厂至关重要。
