Innovative Institute of Animal Healthy Breeding, Guangzhou Key Laboratory of Aquatic Animal Diseases and Waterfowl Breeding, College of Animal Sciences and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou 510222, Guangdong, China; Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, Guangdong, China.
Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, Guangdong, China.
Comp Biochem Physiol B Biochem Mol Biol. 2024 Jan;269:110903. doi: 10.1016/j.cbpb.2023.110903. Epub 2023 Sep 16.
The rabbitfish Siganus canaliculatus was the first marine teleost reported to possess long-chain polyunsaturated fatty acid (LC-PUFA) biosynthetic ability, and the related molecular mechanisms have been well clarified. Here, we investigated the LC-PUFA biosynthesis capability of the congeneric rabbitfish S. guttatus. First, cDNAs of genes for four key enzymes related to LC-PUFA biosynthesis, namely Δ6Δ5 fatty acyl desaturase (fads2) (1335 bp; 445 aa), Δ4 fads2 (1335 bp; 445 aa), and elongation of very long chain fatty acid proteins (elovl5) (873 bp; 291 aa) and elovl4 (906 bp; 302 aa) were cloned from the liver of S. guttatus. The Δ6Δ5 fads2, Δ4 fads2 and elovl5 genes showed high expression in brain, liver, spleen, gallbladder, and intestine but relatively low expression in eye, whereas the elovl4 gene showed specific and high expression in eye. During embryogenesis, mRNA expression of Δ4 fads2 and elovl4 was detected from 8 h post-fertilization (hpf) and then maintained a high level to 24 hpf, while mRNA expression of Δ6Δ5 fads2 and elovl5 reached a peak at 14 hpf but then declined. In addition, ambient salinity (32 ppt and 20 ppt) exerted some regulatory influence on the expression of the four genes during embryogenesis. The levels of C18 PUFA precursors and, especially, PUFA and DHA of the embryos, decreased from 17 hpf to 24 hpf. These results suggested that S. guttatus, similar to the congeneric S. canaliculatus, would have capability for LC-PUFA biosynthesis, which is still not activated at the fertilized egg stage.
尖塘鳢（Siganus canaliculatus）是首例被报道具有长链多不饱和脂肪酸（LC-PUFA）生物合成能力的海洋硬骨鱼类，其相关的分子机制已得到充分阐明。在这里，我们研究了同种尖塘鳢（S. guttatus）的 LC-PUFA 生物合成能力。首先，我们从尖塘鳢肝脏中克隆出与 LC-PUFA 生物合成相关的四个关键酶基因的 cDNA，即 Δ6Δ5 脂肪酸去饱和酶（fads2）（1335bp；445 aa）、Δ4 fads2（1335bp；445 aa）和超长链脂肪酸延伸蛋白（elovl5）（873bp；291 aa）和 elovl4（906bp；302 aa）。Δ6Δ5 fads2、Δ4 fads2 和 elovl5 基因在脑、肝、脾、胆囊和肠中表现出高表达，但在眼组织中表达相对较低，而 elovl4 基因在眼组织中特异性高表达。在胚胎发育过程中，从受精后 8 小时（hpf）开始检测到 Δ4 fads2 和 elovl4 的 mRNA 表达，然后在 24 hpf 时保持高水平，而 Δ6Δ5 fads2 和 elovl5 的 mRNA 表达在 14 hpf 时达到峰值，然后下降。此外，环境盐度（32 ppt 和 20 ppt）在胚胎发育过程中对四个基因的表达有一定的调节作用。从 17 hpf 到 24 hpf，C18 PUFA 前体水平，尤其是 PUFA 和 DHA 水平下降。这些结果表明，与同种的 S. canaliculatus 相似，S. guttatus 具有 LC-PUFA 生物合成能力，但在受精卵阶段尚未激活。
