Sphingolipids are bioactive lipids present in all eukaryotes. Tetrahymena thermophila is a ciliate that displays remarkable sphingolipid moieties, that is, the unusual phosphonate‐linked headgroup ceramides, present in membranes. To date, no identification has been made in this organism of the functions or related genes implicated in sphingolipid metabolism. By gathering information from the T. thermophila genome database together with sphingolipid moieties and enzymatic activities reported in other Tetrahymena species, we were able to reconstruct the putative de novo sphingolipid metabolic pathway in T. thermophila. Orthologous genes of 11 enzymatic steps involved in the biosynthesis and degradation pathways were retrieved. No genes related to glycosphingolipid or phosphonosphingolipid headgroup transfer were found, suggesting that both conserved and innovative mechanisms are used in ciliate. The knockout of gene TTHERM_00463850 allowed to identify the gene encoding a putative fatty acid 2‐hydroxylase, which is involved in the biosynthesis pathway. Knockout cells have shown several impairments in the sexual stage of conjugation since different mating types of knockout strains failed to form cell pairs and complete the conjugation process. This fatty acid 2‐hydroxylase gene is the first gene of a sphingolipid metabolic pathway to be identified in ciliates and have a critical role in their sexual stage.

中文翻译：

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嗜热四膜虫鞘脂代谢相关基因的基因组分析和参与接合有性阶段的脂肪酸 2-羟化酶的鉴定。

鞘脂是存在于所有真核生物中的生物活性脂质。嗜热四膜虫是一种纤毛虫，显示出显着的鞘脂部分，即存在于膜中的不寻常的膦酸酯连接的头部神经酰胺。迄今为止，尚未在该生物体中鉴定出与鞘脂代谢有关的功能或相关基因。通过从T. thermophila基因组数据库中收集信息以及在其他四膜虫物种中报告的鞘脂部分和酶活性，我们能够重建T. thermophila 中假定的从头鞘脂代谢途径. 检索了涉及生物合成和降解途径的 11 个酶促步骤的直系同源基因。没有发现与鞘糖脂或鞘脂头部基团转移相关的基因，这表明在纤毛虫中使用了保守和创新的机制。基因 TTHERM_00463850 的敲除允许鉴定编码假定的脂肪酸 2-羟化酶的基因，该基因参与生物合成途径。由于不同交配类型的敲除菌株未能形成细胞对并完成结合过程，因此敲除细胞在结合的有性阶段表现出多种损伤。这种脂肪酸 2-羟化酶基因是第一个在纤毛虫中发现的鞘脂代谢途径的基因，在它们的性阶段起着关键作用。