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Front. Genet. | doi: 10.3389/fgene.2019.00961

Non-additive and asymmetric allelic expression of growth hormone in hybrid tilapia

 Huan Zhong1, Xiaojin Zhang2, Qian Xu3, Jinpeng Yan3, Zhuojun Han4, Huifang Zheng4, Jun Xiao1,  Zhanyang Tang1, Fenghua Wang5, Yongju Luo1 and  Yi Zhou1*
  • 1Guangxi Academy of Fishery Sciences, China
  • 2Shanghai Ocean University, China
  • 3Central South University, China
  • 4Guangxi University, China
  • 5Xinjiang Normal University, China

Hybridization is a common breeding technique that can improve germplasm through heterosis in aquaculture. However, the regulation of key gene expression, including the details of transcriptional level changes at the beginning of hybridization events, remains largely undefined, especially in teleosts. In this study, by interspecies crossing between two pure lines of Nile tilapia and blue tilapia, we obtained a hybrid tilapia population as a model to elucidate heterosis, and we traced the molecular outcomes of growth hormone (GH) expression and allele-specific expression (ASE) in hybrids. The hybrids display growth vigor compared to their parents in the 120-day growth trial. GH mRNA expression was uniquely expressed in the pituitary. The overall expression of GH in the hybrid was significantly higher than in its parents. In addition, higher GH expression was found in the hybrid than the mid-parent value, in both males and females, showing a non-additive pattern. We identified four SNP sites between Nile tilapia and blue tilapia. Subsequently, by pyrosequencing, we found asymmetric allelic expression in hybrids with higher maternal allelic transcript ratios in both males and females. Fasting significantly increased GH expression in hybrids, but asymmetric allelic expression was not affected by feeding or fasting conditions. Finally, we identified cis and trans effects via overall expression and ASE values in the hybrid, which showed that the cis and trans effects promoted the expression of maternal subgenome in the hybrid, contributing to the expression superiority of GH in hybrid tilapia. Taken together, the results of our study first illustrated the concept of GH expression superiority and its formation mechanism in hybrid fish with growth vigor.

Keywords: Growth Hormone, Tilapia, Hybrid, heterosis, Allele specific expression, non-additive expression

Received: 25 May 2019; Accepted: 09 Sep 2019.

Copyright: © 2019 Zhong, Zhang, Xu, Yan, Han, Zheng, Xiao, Tang, Wang, Luo and Zhou. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mx. Yi Zhou, Guangxi Academy of Fishery Sciences, Nanning, Guangxi Zhuang Region, China, zhouyi1982cn@126.com