Abstract Elongation of very long-chain fatty acids 4 (Elovl4) proteins, belong to the fatty acyl elongase families that are involved in long-chain polyunsaturated fatty acids (LC-PUFA) biosynthesis in animals. Thus far, very little is known about the roles of Elovl4 in fish. Previously, we reported an elovl4 gene named as elovl4b in rabbitfish (Siganus canaliculatus). In this study, a novel elovl4-like gene with a 957-bp open reading frame encoding a 318 amino-acid protein, which shared 67.3% similarity with rabbitfish Elovl4b and more than 80% similarity with Elovl4a from other teleost, was identified in S. canaliculatus, and thus was termed as elovl4a. Multiple protein sequences alignment, gene synteny and phylogenetic analysis indicated that two obviously different elovl4 genes are widespread in various teleost. Different with elovl4b (mainly expressed in eye and slightly expressed in brain), rabbitfish elovl4a was primarily distributed in brain, slightly examined in eye and gonad tissues while hardly detectable in other tissues. The transcription of cerebral elovl4a was significantly higher in fishes cultured in seawater (32‰) than that of those maintained at a brackish water environment (15‰), when fishes were fed with a vegetable oil (VO) enriched diet. However, the transcriptional pattern was totally inverse when fishes were fed with a fish oil (FO) enriched diet. In the brackish water, diet types had no effect on the transcription of cerebral elovl4a. Whereas in seawater, the transcription of cerebral elovl4a was significantly higher in fishes fed with the VO diet in comparison with those fed with the FO diet. Our findings suggest that elovl4a can be regulated by both nutritional and osmotic factors, and it may play an important role in endogenous biosynthesis of LC-PUFA in the neural system of rabbitfish. This study may help us to understand the effects of nutritional and osmotic factors on the LC-PUFA biosynthesis, as well as contribute to the optimization or enhancement of LC-PUFA biosynthesis in teleost.

中文翻译：

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一种新的 elovl4 基因的全基因组鉴定及其响应兔鱼（Siganus canaliculatus）营养和渗透调节的转录

摘要 超长链脂肪酸延长 4 (Elovl4) 蛋白属于脂肪酰基延长酶家族，参与动物的长链多不饱和脂肪酸 (LC-PUFA) 生物合成。到目前为止，对 Elovl4 在鱼类中的作用知之甚少。以前，我们报道了在兔鱼（Siganus canaliculatus）中命名为 elovl4b 的 elovl4 基因。在这项研究中，在 S . canaliculatus，因此被称为elovl4a。多蛋白序列比对、基因同线性和系统发育分析表明，两个明显不同的elovl4基因广泛存在于各种硬骨鱼中。与elovl4b（主要在眼部表达，脑部微表达）不同，兔鱼elovl4a主要分布于脑部，在眼部和性腺组织中略有检测，在其他组织中几乎检测不到。当鱼类饲喂富含植物油 (VO) 的饮食时，在海水中养殖的鱼类 (32‰) 的脑 elovl4a 转录显着高于维持在咸水环境中的鱼类 (15‰)。然而，当鱼喂食富含鱼油 (FO) 的饮食时，转录模式完全相反。在微咸水中，饮食类型对大脑 elovl4a 的转录没有影响。而在海水中，与喂食 FO 饮食的鱼相比，喂食 VO 饮食的鱼的脑 elovl4a 转录显着更高。我们的研究结果表明，elovl4a 可以受营养和渗透因子的调节，并且它可能在兔鱼神经系统中 LC-PUFA 的内源生物合成中起重要作用。这项研究可能有助于我们了解营养和渗透因子对 LC-PUFA 生物合成的影响，并有助于优化或增强硬骨鱼中 LC-PUFA 的生物合成。