Effects of hatching enzymes on egg envelope digestion in the male‐brooding seahorse
Effects of hatching enzymes on egg envelope digestion in the male‐brooding seahorse
复制标题
孵化酶对雄性育雏海马卵膜消化的影响
DOI：
10.1002/mrd.23474
复制
发表时间：
2021
影响因子：
2.5
通讯作者：
Q. Lin
中科院分区：
文献类型：
--
作者：
Huixian Zhang;Bo Zhang;M. Kawaguchi;Q. Lin
本研究旨在评价孵化酶对雄性孵化海马孵化期卵膜消化的影响。从直立海马体中克隆了两种孵化酶基因--高绒毛膜溶血酶(HCE)和低绒毛膜溶血酶(LCE)的互补DNA，并对其进行了功能分析。基因组同时性分析证实，硬骨鱼具有LCE基因同源性。相反，HCE的基因组位置在海龙鱼中被发现是保守的，但在其他硬骨鱼中不是，这表明易位到一个新的基因组位置发生了。整体原位杂交结果显示，孵化的腺体细胞表达HCE和LCE基因。为了确定HCE和LCE在孵化过程中的消化机制，制备了重组HCE和LCE，并用受精卵包膜和合成肽检测了它们的酶活性。海马、HCE和LCE独立消化和软化了衬里海马的卵囊。虽然HCE和LCE共处理后卵被膜消化较多，但未观察到包膜增溶现象。事实上，HCE和LCE对四种不同的合成肽都表现出相似的底物特异性，这些合成肽是从鸡蛋被膜蛋白的裂解部位设计的。其他真鱼纲鱼类的HCE和LCE蛋白表现出不同的特异性，在HCE和LCE的协同作用下，卵膜被溶解。这些结果表明，斑马LCE的功能发生了退化。我们的结果暗示了雄性妊娠卵胎生鱼类进化适应的消化机制。
In the present study, we aimed to evaluate the effects of hatching enzymes on the egg envelope digestion during the hatching period in the male brooding seahorse. The complementary DNAs encoding two hatching‐enzyme genes, high choriolytic enzyme (HCE) and low choriolytic enzyme (LCE), were cloned and functionally characterized from the lined seahorse (Hippocampus erectus). The genomic‐synteny analysis confirmed that teleosts shared LCE gene synteny. In contrast, the genomic location of HCE was found to be conserved with pipefish, but not other teleosts, suggesting that translocation into a novel genomic location occurred. Whole‐mount in situ hybridization showed that HCE and LCE mRNAs were expressed in hatching gland cells. To determine the digestion mechanisms of HCE and LCE in hatching, recombinant HCE and LCE were generated and their enzyme activities were examined using fertilized egg envelopes and synthetic peptides. Seahorse HCE and LCE independently digested and softened the egg envelopes of the lined seahorse. Although the egg envelope was digested more following HCE and LCE co‐treatment, envelope solubilization was not observed. Indeed, both HCE and LCE showed similar substrate specificities toward four different synthetic peptides designed from the cleavage sites of egg envelope proteins. HCE and LCE proteins from other euteleostean fishes showed different specificities, and the egg envelope was solubilized by the cooperative action of HCE and LCE. These results suggest that the function of LCE was degenerated in the lined seahorse. Our results imply a digestion mechanism for evolutionary adaptation in ovoviviparous fish with male pregnancy.