CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510300, PR China; Sanya Institute of Ocean Eco-Environmental Engineering, Sanya, 572000, PR China.
Zhongkai university of Agriculture and Engineering, Guangzhou, 510225, PR China.
Dev Comp Immunol. 2023 May;142:104654. doi: 10.1016/j.dci.2023.104654. Epub 2023 Feb 2.
Seahorses are one of the most amazing ovoviviparous fishes in the ocean because males, and not females, have evolved a brood pouch for incubating embryos. During male pregnancy, paternal seahorses need to develop effective immune protection for embryos in the brood pouch from potential infection by pathogens. Lysozymes (Lyz) are a group of antibacterial enzymes of the innate immune system that play an important role in resisting pathogen invasion. However, the immune function of lysozymes in the brood pouch of the pregnancy-lined seahorse (Hippocampus erectus) remains unknown. In this study, we found three different lysozymes in the lined seahorse: HeLyzC, HeLyzG1, and HeLyzG2. Synteny analysis revealed that HeLyzG1 and HeLyzG2 were generated by species-specific expansion rather than tandem duplication. Tissue expression patterns showed that the highest mRNA expression levels of the three lysozymes occurred in the brood pouches. Immunostimulation-induced expression analysis showed that all three HeLyzs in the brood pouches up-regulated their mRNA expression levels after Vibrio parahaemolyticus infection, but only the HeLyzG2 was upregulated after Poly(I:C) injection. Similarly, except for HeLyzC, upregulated expressions of HeLyzG1 and HeLyzG2 were found quickly in brood pouches injected with LPS. The upregulated levels of HeLyzC and HeLyzG2 in brood pouches during pregnancy were significantly higher than those in non-pregnancy, implying that seahorse lysozymes might function in the immune defense in brood pouches during pregnancy. In addition, the expression levels of HeLyzs were low in embryos in the brood pouch but significantly increased in neonates. This implies that embryos in the brood pouch might not necessarily express more lysozymes by themselves due to paternal immune protection. In conclusion, our study demonstrated that HeLyzs play an important role in immune protection during male seahorse gestation, and the synergistic effect of multiple HeLyzs may contribute to improved neonatal survival.
海马是海洋中最令人惊奇的卵胎生鱼类之一，因为雄性（而不是雌性）进化出了育囊来孵化胚胎。在雄性怀孕过程中，亲海马需要为育囊中的胚胎发育出有效的免疫保护，以防止潜在的病原体感染。溶菌酶（Lyz）是先天免疫系统中的一组抗菌酶，在抵抗病原体入侵方面发挥着重要作用。然而，怀孕线纹海马（Hippocampus erectus）育囊中线溶酶的免疫功能尚不清楚。在这项研究中，我们在线纹海马中发现了三种不同的溶菌酶：HeLyzC、HeLyzG1 和 HeLyzG2。基因同线性分析表明，HeLyzG1 和 HeLyzG2 是由种特异性扩张而不是串联重复产生的。组织表达模式表明，这三种溶菌酶的 mRNA 表达水平在育囊中最高。免疫刺激诱导表达分析表明，三种 HeLyzs 在育囊中均在感染副溶血弧菌后上调其 mRNA 表达水平，但仅在注射 Poly(I:C)后上调 HeLyzG2。同样，除了 HeLyzC 之外，在注射 LPS 后，HeLyzG1 和 HeLyzG2 在育囊中也迅速上调表达。怀孕期间育囊中 HeLyzC 和 HeLyzG2 的上调水平明显高于非怀孕期，这表明海马溶菌酶可能在怀孕期间育囊中发挥免疫防御作用。此外，HeLyzs 在育囊中的胚胎中的表达水平较低，但在新生儿中显著增加。这意味着胚胎在育囊中可能不一定因父系免疫保护而自身表达更多的溶菌酶。总之，我们的研究表明，HeLyzs 在雄性海马怀孕期间的免疫保护中发挥着重要作用，多种 HeLyzs 的协同作用可能有助于提高新生儿的存活率。
