State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, People's Republic of China.
Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, 361102, People's Republic of China.
BMC Genomics. 2021 Sep 8;22(1):650. doi: 10.1186/s12864-021-07954-y.
Heterosis has been exploited for decades in different animals and crops due to it resulting in dramatic increases in yield and adaptability. Hybridization is a classical breeding method that can effectively improve the genetic characteristics of organisms through heterosis. Abalone has become an increasingly economically important aquaculture resource with high commercial value. However, due to changing climate, abalone is now facing serious threats of high temperature in summer. Interspecific hybrid abalone (Haliotis gigantea ♀ × H. discus hannai ♂, SD) has been cultured at large scale in southern China and has been shown high survival rates under heat stress in summer. Therefore, SD has become a good model material for heterosis research, but the molecular basis of heterosis remains elusive.
Heterosis in thermal tolerance of SD was verified through Arrhenius break temperatures (ABT) of cardiac performance in this study. Then RNA-Sequencing was conducted to obtain gene expression patterns and alternative splicing events at control temperature (20 °C) and heat stress temperature (30 °C). A total of 356 (317 genes), 476 (435genes), and 876 (726 genes) significantly diverged alternative splicing events were identified in H. discus hannai (DD), H. gigantea (SS), and SD in response to heat stress, respectively. In the heat stress groups, 93.37% (20,512 of 21,969) of the expressed genes showed non-additive expression patterns, and over-dominance expression patterns of genes account for the highest proportion (40.15%). KEGG pathway enrichment analysis showed that the overlapping genes among common DEGs and NAGs were significantly enriched in protein processing in the endoplasmic reticulum, mitophagy, and NF-κB signaling pathway. In addition, we found that among these overlap genes, 39 genes had undergone alternative splicing events in SD. These pathways and genes may play an important role in the thermal resistance of hybrid abalone.
More alternative splicing events and non-additive expressed genes were detected in hybrid under heat stress and this may contribute to its thermal heterosis. These results might provide clues as to how hybrid abalone has a better physiological regulation ability than its parents under heat stress, to increase our understanding of heterosis in abalone.
杂种优势在不同的动物和作物中已经被利用了几十年，因为它导致产量和适应性的显著提高。杂交是一种经典的育种方法，可以通过杂种优势有效地改善生物体的遗传特性。鲍鱼已经成为一种越来越重要的具有高商业价值的水产养殖资源。然而，由于气候变化，鲍鱼现在面临着夏季高温的严重威胁。中国南方已经大规模养殖了种间杂交鲍（♀Haliotis gigantea ×♂H. discus hannai，SD），并且在夏季高温胁迫下表现出很高的存活率。因此，SD 已经成为杂种优势研究的一个很好的模型材料，但杂种优势的分子基础仍然难以捉摸。
本研究通过心脏功能的 Arrhenius 断裂温度（ABT）验证了 SD 在热耐受性方面的杂种优势。然后在对照温度（20°C）和热应激温度（30°C）下进行 RNA 测序，以获得基因表达模式和选择性剪接事件。在 H. discus hannai（DD）、H. gigantea（SS）和 SD 中，分别有 356（317 个基因）、476（435 个基因）和 876（726 个基因）个显著差异的选择性剪接事件对热应激作出响应。在热应激组中，93.37%（21969 个中的 20512 个）表达基因表现出非加性表达模式，并且基因的过显性表达模式占比最高（40.15%）。KEGG 通路富集分析表明，在共差异表达基因和非加性表达基因的重叠基因中，内质网蛋白加工、线粒体自噬和 NF-κB 信号通路显著富集。此外，我们发现这些重叠基因中有 39 个基因在 SD 中发生了选择性剪接事件。这些通路和基因可能在杂交鲍的耐热性中发挥重要作用。
在热应激下，杂种中检测到更多的选择性剪接事件和非加性表达基因，这可能有助于其耐热杂种优势。这些结果可能为我们提供线索，了解杂交鲍在热应激下如何比其亲本具有更好的生理调节能力，从而增加我们对鲍鱼杂种优势的理解。
