为了探究水流对鱼类体色的影响,比较了不同流速水流养殖下斑马鱼皮肤黑色素细胞数量和基因的表达,结果表明：相对于低流速（0.010 m/s）,在高流速（0.022 m/s）下养殖斑马鱼3个月后,皮肤黑色素细胞数量显著增加,尤其是鱼体尾部区域；实时荧光定量PCR（RT-qPCR）结果显示高流速组斑马鱼皮肤黑色素细胞标记基因kita、mitfa和tyrp1a相对表达量显著升高,黄色素细胞标记基因csf1ra显著降低,虹彩细胞标记基因pnp4a无显著变化,表明高流速水流诱导黑色素细胞而抑制黄色素细胞的形成。RT-qPCR结果显示,相比于低流速组,高流速组斑马鱼皮肤中黑色素细胞形成抑制因子基因asip1的相对表达量显著减少,与黑色素细胞形成相关的黑皮质素受体基因mc1r、阿黑皮素原基因pomca无显著性变化,视黄酸合成相关的视黄醛脱氢酶基因raldh2和raldh3显著下调,提示水流刺激可通过降低asip1的表达来诱导黑色素细胞形成；水流刺激瞬时受体通道蛋白基因trpv4和压电式机械敏感通道蛋白基因piezo2的表达上调,而piezo1无显著性变化。以上结果表明,水流能诱导斑马鱼黑色素细胞的形成,可能是通过皮肤机械力感受蛋白Trpv4或Piezo2介导水流刺激减少asip1表达的结果。Asip1除了调控黑色素细胞形成以外还调控脂肪的积累,相比于低流速组,高流速组斑马鱼肥满度也显著下降,GO富集分析显示差异表达基因主要富集到甘油三酯分解代谢、高密度脂蛋白颗粒、脂质结合等条目,差异表达基因显著富集的KEGG通路有：氨基糖和核苷酸糖的代谢、PPAR信号通路、亚油酸代谢、花生四烯酸代谢等。RT-qPCR检测与脂肪代谢相关的脂肪酸过饱和酶2基因fads2显著上调,瘦素基因lep无显著性差异,提示水流可能通过Asip1影响Fads2进而影响脂肪降解。本研究首次报道了水流对鱼类体色的影响,为理解目前越来越普遍的流水养殖对鱼类体色和肥满度的影响提供了初步的理论基础。

To investigate the effects of water flow on fish body color, the number of melanophore and gene expression in zebrafish skin were investigated under water flow culture with two different flow rates 0.010 m/s (low flow rate) and 0.022 m/s (high flow rate). The results showed that compared with low flow rate, the number of skin melanophore increased significantly after 3 months of culturing zebrafish under higher flow rate, especially in the caudal region of the body of the fish, the expression levels of the skin melanophore marker genes kita, mitfa and tyrp1a were significantly increased as well. Meanwhile, the relative expression level of the xanthophore marker gene csf1ra was significantly decreased, and there was no significant change in the iridophore marker gene pnp4a, indicating that the high flow rate water induced the formation of melanophore and inhibited the formation of xanthophore. The RT-qPCR results showed that the expression of melanophore formation inhibitor gene asip1 was significantly decreased in the skin of zebrafish in the high-flow group compared with that in the low-flow group； the melanocortin receptor gene mc1r and the amelanocortinogen gene pomca, which are related to melanophore formation, were not significantly changed； and the retinoid dehydrogenase genes raldh2 and raldh3, which are related to retinoic acid synthesis, were significantly down-regulated； water flow stimulation upregulated the transient receptor channel protein gene trpv4 and the piezoelectric mechanosensitive channel protein gene piezo2, whereas there was no significant change in piezo1. The above results indicate that the high flow rate water flow induces melanophore formation in zebrafish, possibly as a result of reduced asip1 expression mediated by water flow stimulation through the skin mechanosensitive proteins Trpv4 and Piezo2. Asip1 regulates fat accumulation in addition to melanophore formation, and indeed zebrafish body fullness reduces significantly in the high water flow group compared with low flow rate group. GO enrichment analysiss showed differentially expressed genes was mainly enriched to entries for triglyceride catabolism, HDL particles, lipid binding, etc and differentially expressed genes was significantly enriched in the following KEGG pathways： aminoglycan and nucleotide sugar metabolism, PPAR signaling pathway, linoleic acid metabolism, and arachidonic acid metabolism, etc. RT-qPCR showed the fatty acid peroxidase 2 gene fads2, which is associated with lipid metabolism, was significantly up-regulated, and there was no significant difference in the leptin gene lep, indicating that water flow may affect fat degradation through Asip1 affecting Fads2. In conclusion, this study for the first time reported the effect of water flow on fish body color and proposed a preliminary signaling regulatory pathway, which provides a preliminary theoretical basis for understanding the effect of water flow culture on fish body color and fullness.

S917

国家重点研发计划(2022YFD2400401)