Surm Joachim M, Prentis Peter J, Pavasovic Ana
School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, 2 George Street, Brisbane, Qld 4000, Australia.
School of Earth, Environmental and Biological Sciences, Science and Engineering Faculty, Queensland University of Technology, 2 George Street, Brisbane, Qld 4000, Australia.
PLoS One. 2015 Aug 26;10(8):e0136301. doi: 10.1371/journal.pone.0136301. eCollection 2015.
Recent research has identified marine molluscs as an excellent source of omega-3 long-chain polyunsaturated fatty acids (lcPUFAs), based on their potential for endogenous synthesis of lcPUFAs. In this study we generated a representative list of fatty acyl desaturase (Fad) and elongation of very long-chain fatty acid (Elovl) genes from major orders of Phylum Mollusca, through the interrogation of transcriptome and genome sequences, and various publicly available databases. We have identified novel and uncharacterised Fad and Elovl sequences in the following species: Anadara trapezia, Nerita albicilla, Nerita melanotragus, Crassostrea gigas, Lottia gigantea, Aplysia californica, Loligo pealeii and Chlamys farreri. Based on alignments of translated protein sequences of Fad and Elovl genes, the haeme binding motif and histidine boxes of Fad proteins, and the histidine box and seventeen important amino acids in Elovl proteins, were highly conserved. Phylogenetic analysis of aligned reference sequences was used to reconstruct the evolutionary relationships for Fad and Elovl genes separately. Multiple, well resolved clades for both the Fad and Elovl sequences were observed, suggesting that repeated rounds of gene duplication best explain the distribution of Fad and Elovl proteins across the major orders of molluscs. For Elovl sequences, one clade contained the functionally characterised Elovl5 proteins, while another clade contained proteins hypothesised to have Elovl4 function. Additional well resolved clades consisted only of uncharacterised Elovl sequences. One clade from the Fad phylogeny contained only uncharacterised proteins, while the other clade contained functionally characterised delta-5 desaturase proteins. The discovery of an uncharacterised Fad clade is particularly interesting as these divergent proteins may have novel functions. Overall, this paper presents a number of novel Fad and Elovl genes suggesting that many mollusc groups possess most of the required enzymes for the synthesis of lcPUFAs.
近期研究已确认海洋软体动物是ω-3长链多不饱和脂肪酸（lcPUFAs）的优质来源，这基于它们内源性合成lcPUFAs的潜力。在本研究中，我们通过查询转录组和基因组序列以及各种公开可用数据库，生成了一份来自软体动物门主要目类的脂肪酸去饱和酶（Fad）和极长链脂肪酸延长酶（Elovl）基因的代表性列表。我们在以下物种中鉴定出了新的且未表征的Fad和Elovl序列：梯形蚶、白纹蜒螺、黑纹蜒螺、太平洋牡蛎、加州海兔、皮氏枪乌贼和栉孔扇贝。基于Fad和Elovl基因翻译后的蛋白质序列比对，Fad蛋白的血红素结合基序和组氨酸盒以及Elovl蛋白的组氨酸盒和十七个重要氨基酸高度保守。对排列好的参考序列进行系统发育分析，分别重建Fad和Elovl基因的进化关系。观察到Fad和Elovl序列都有多个解析良好的进化枝，这表明基因重复的多轮发生最能解释Fad和Elovl蛋白在软体动物主要目类中的分布。对于Elovl序列，一个进化枝包含功能已表征的Elovl5蛋白，而另一个进化枝包含推测具有Elovl4功能的蛋白。其他解析良好的进化枝仅由未表征的Elovl序列组成。Fad系统发育中的一个进化枝仅包含未表征的蛋白，而另一个进化枝包含功能已表征的δ-5去饱和酶蛋白。未表征的Fad进化枝的发现尤其有趣，因为这些不同的蛋白可能具有新功能。总体而言，本文展示了许多新的Fad和Elovl基因，表明许多软体动物类群拥有合成lcPUFAs所需的大部分酶。
