State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China; College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen 361102, China; Tianjin Key Laboratory of Aqua-Ecology and Aquaculture, College of Fisheries, Tianjin Agricultural University, Tianjin 300384, China.
State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China; College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen 361102, China.
Fish Shellfish Immunol. 2018 Jan;72:679-689. doi: 10.1016/j.fsi.2017.11.009. Epub 2017 Nov 7.
Hybridization is an effective way of improving germplasm in abalone, as it often generates benign traits in the hybrids. The hybrids of Haliotis discus hannai and H. gigantea have shown heterosis in terms of disease resistance than one or both parental species. In the present study, to elucidate the physiological and molecular mechanism of this heterosis, we analyzed the dynamic changes of several immune indexes including survival rate, total circulating haemocyte count (THC), phagocytic activity, reactive oxygen species level (ROS) and phenoloxidase activity (PO) in two parental species, H. discus hannai (DD) and H. gigantea (GG), and their reciprocal hybrids H. discus hannai ♀ × H. gigantea ♂ (DG), H. gigantea ♀ × H. discus hannai ♂ (GD) challenged with a mixture of Vibrio harveyi, V. alginolyticus and V. parahaemolyticus (which have been demonstrated to be pathogenic to abalone). Besides, we cloned and analyzed three important immune genes: heat shock protein 70 (hsp70), ferritin and cold shock domain protein (csdp) in H. discus hannai and H. gigantea, then further investigated their mRNA level changes in the four abalone genotypes after bacterial challenge. Results showed that these physiological and molecular parameters were significantly induced by bacterial exposure, and their changing patterns were obviously different between the four genotypes: (1) Survival rates of the two hybrids were higher than both parental species after bacterial exposure; (2) DG had higher THC than the other three genotypes; (3) Phagocytosis responded slower in the hybrids than in the parental species; (4) DD's ROS level was lower than the other three genotypes at 48 h post infection; (5) Phenoloxidase activity was lower in DD during the infection compared to the other genotypes; (6) mRNA levels of hsp70 and csdp, were always lower in at least one parental species (DD) than in the hybrids after the bacterial exposure. Results from this study indicate that the hybrids are more active or efficient in immune system function, hence they could effectively defense against a bacterial invasion, leading to higher survival rates after challenge. This study provides physiological and molecular evidences for interpreting the disease resistant heterosis in this abalone hybrid system, which could help us in a better understanding and utilization of heterosis in abalone aquaculture.
杂交是改良鲍鱼种质的有效方法，因为它通常会在杂种中产生良性特征。与一个或两个亲本种相比，盘鲍（Haliotis discus hannai）和皱纹盘鲍（H. gigantea）的杂种在抗病性方面表现出杂种优势。在本研究中，为了阐明这种杂种优势的生理和分子机制，我们分析了两个亲本种（H. discus hannai（DD）和 H. gigantea（GG））以及它们的正反交杂种（H. discus hannai♀×H. gigantea♂（DG）和 H. gigantea♀×H. discus hannai♂（GD））在受到哈维氏弧菌、溶藻弧菌和副溶血弧菌混合物刺激时几种免疫指标的动态变化，这些菌已被证明对鲍鱼具有致病性。此外，我们克隆并分析了 H. discus hannai 和 H. gigantea 中的三个重要免疫基因：热休克蛋白 70（hsp70）、铁蛋白和冷休克结构域蛋白（csdp），然后进一步研究了它们在细菌刺激后四种鲍鱼基因型中的 mRNA 水平变化。结果表明，这些生理和分子参数均被细菌暴露显著诱导，并且它们在四种基因型之间的变化模式明显不同：（1）细菌暴露后，两种杂种的存活率均高于两个亲本种；（2）DG 的总循环血细胞计数（THC）高于其他三种基因型；（3）杂种的吞噬作用比亲本种响应更慢；（4）感染后 48 小时，DD 的 ROS 水平低于其他三种基因型；（5）感染期间，DD 的酚氧化酶活性比其他基因型低；（6）细菌暴露后，至少一种亲本种（DD）的 hsp70 和 csdp 的 mRNA 水平始终低于杂种。本研究结果表明，杂种在免疫系统功能方面更为活跃或高效，因此它们可以有效抵御细菌入侵，从而在受到挑战后提高存活率。本研究为解释该鲍鱼杂交系统中抗病杂种优势提供了生理和分子证据，有助于我们更好地理解和利用鲍鱼养殖中的杂种优势。
