As a promising species of the thraustochytrids, Schizochytrium sp. has attracted extensive attention due to its ability to produce high levels of polyunsaturated fatty acids. In Schizochytrium sp. HX-308, there was a complete anaerobic polyketide synthase (PKS) pathway and an incomplete aerobic desaturase/elongase pathway. However, it is still quite unclear which fatty acid desaturases are involved in fatty acid desaturation in Schizochytrium sp. and how they act in concert. In this work, we firstly identified five putative desaturases in Schizochytrium sp. HX-308, including Δ12, two Δ8, Δ6, and Δ5 fatty acid desaturase genes. They were heterologously expressed in Yarrowia lipolytica and the first four fatty acid desaturases were verified as functional. Δ12 desaturase contributes to a significant increase in the content of C18:2Δ^{9, 12} fatty acids, from 17.26 % to 28.46 %. The expression of two Δ8 desaturases resulted in an increase in C20:3Δ^{8, 11, 14} content, from 3.84 % to 7.29 % and 6.82 %, respectively. Δ6 desaturase enables the PO1F strain to produce a new fatty acid C18:3Δ^{6, 9, 12}, reaching 9.73 % of the total fatty acids. Although the expression of Δ5 desaturase didn't produce C20:4 Δ^{5, 8, 11, 14} fatty acids, it significantly decreased the content of C18:1Δ⁹ and C18:2Δ^{9, 12} fatty acids and largely significantly increased C18:3Δ^{6, 9, 12} and C20:2Δ^{11, 14} fatty acid content. This work will provide valuable insights into the optimization of the polyunsaturated fatty acid composition of Schizochytrium sp. through genetic engineering in the future.

作为破囊壶菌的一个有前途的物种，裂殖壶菌属。由于其能够产生高水平的多不饱和脂肪酸而引起了广泛的关注。在裂殖壶菌属中。HX-308，存在完整的厌氧聚酮化合物合成酶（PKS）途径和不完整的好氧去饱和酶/延长酶途径。然而，尚不清楚哪些脂肪酸去饱和酶参与了裂殖壶菌属中的脂肪酸去饱和。以及它们如何协同行动。在这项工作中，我们首先在裂殖壶菌属中鉴定了五种推定的去饱和酶。HX-308，包括Δ12、两个Δ8、Δ6和Δ5脂肪酸去饱和酶基因。它们在解脂耶氏酵母中异源表达前四种脂肪酸去饱和酶被证实是有功能的。Δ12 去饱和酶有助于 C18:2Δ9 ^{, 12}脂肪酸的含量显着增加，从 17.26 % 提高到 28.46 %。两种 Δ8 去饱和酶的表达导致 C20:3Δ 8、11、14^含量分别从 3.84% 增加到 7.29% 和 6.82%。Δ6去饱和酶使PO1F菌株能够产生新的脂肪酸C18:3Δ ^{6, 9, 12}，达到总脂肪酸的9.73%。Δ5去饱和酶的表达虽然不产生C20: 4Δ5,8,11,14脂肪酸，但显着降低了C18:1Δ9^和C18 : ^2Δ9,12脂肪酸的含量，显着增加了C18:3Δ ^6、9、12和 C20:2Δ ^{11, 14}脂肪酸含量。这项工作将为优化裂殖壶菌的多不饱和脂肪酸组成提供有价值的见解。未来通过基因工程。