Proteomic analysis of muscle between hybrid abalone and parental lines Haliotis gigantea Reeve and Haliotis discus hannai Ino
G Di1,2, X Luo1, W You1, J Zhao1, X Kong2 and C Ke1
To understand the potential molecular mechanism of heterosis, protein expression patterns were compared from hybrids of
Haliotis gigantea (G) and Haliotis discus hannai (D) using two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight/time-of-flight analyses. Expression differences were observed in muscle samples from the four groups with 673±21.0 stained spots for H. discus hannai ♀×H. discus hannai ♂ (DD), 692±25.6 for H. gigantea ♀×H. gigantea ♂ (GG), 679±16.2 for H. discus hannai ♀×H. gigantea ♂ (DG) (F1 hybrid) and 700±19 for H. gigantea ♀×H. discus hannai ♂ (GD) (F1 hybrid). Different 2-DE image muscle protein spots had a mirrored relationship between purebreds and the F1 hybrid, suggesting that all stained spots in F1 hybrid muscle were on 2-DEs from parents. DD and DG clustered together first, and then clustered with GD, whereas the distance of DD and GG was maximal according to hierarchical cluster analysis. We identified 136 differentially expressed protein spots involved in major biological processes, including energy metabolism and stress response. Most energy metabolism proteins were additive, and stress-induced proteins displayed additivity or overdominance. In these 136 identified protein spots, hybrid offspring with additivity or over-dominance accounted for 68.38%.
Data show that a proteomic approach can provide functional prediction of abalone interspecific hybridization.
Heredity advance online publication, 11 February 2015; doi:10.1038/hdy.2014.124
The abalone is an aquatic animal of economic importance and China produces the most abalone (exceeding 50 000 tons per annum). In
China, long-term artificial reproduction and rafferty mating of farmed abalone has led to severe inbreeding and germplasm degradation manifested by individual miniaturization and poor disease resistance.
Along with deterioration of the aquacultural environment, disease outbreaks and other issues cause massive deaths of cultured abalone (Zhang et al., 2004). Recently, hybridization has been shown to be effective and useful for shellfish genetic improvement programs (Elliott, 2000). Heterosis, or the strengthening of different hybrid characteristics, suggests the possibility of obtaining genetically superior individuals by combining parental virtues.
In China, Haliotis discus hannai Ino is an economically important gastropod with large-scale cultivation dating back to the late 1980s (Luo et al., 2010). Several problems emerged in the H. discus hannai industry associated with long-term cultivation, such as quality degeneration, and declines in disease resistance. Haliotis gigantea is a valued commercial species along the coast of Japan, and our research team first introduced H. gigantea from Japan into the Fujian Province for mariculture in 2003 and subsequent artificial propagation was successful (Luo et al., 2010). The meat of H. gigantea is crisp and tender, and H. gigantea has excellent disease resistance (Luo et al., 2010), all traits that make it an important commercial aquaculture species for China. To improve growth and disease resistance, hybridization of H. gigantea and H. discus hannai was performed.
With karyotype analysis, amplified fragment length polymorphism, microsatellite and mitochondrial 16S rRNA and cytochrome c oxidase subunit I gene sequences, morphological, cytological and molecular characterizations of hybrids and pure progenies were conducted, and hybrid status was confirmed (Luo et al., 2010). We confirmed (in 2012) that the growth rate of hybrids was faster than H. discus hannai and H. gigantea at 100 days postfertilization. Survival of the reciprocal hybrid was significantly higher than H. discus hannai as well. Previous work (Luo 2009; Luo et al., 2013) indicated that interspecific hybrid abalone (H. discus hannai×H. gigantea) grow better and have greater environmental adaptability than parental species at 540 days postfertilization; thus the hybrid exhibits heterosis.
Although hybrid vigor has been exploited in agricultural crops, the molecular mechanisms responsible for this basic biological phenomenon are not well understood (Xiang et al., 2013). Recently, some studies suggest that hybridization between two parents can cause changes in gene expression, which may be responsible for heterosis (Xiang et al., 2013). Although relatively new genomics for genetic breeding studies concentrate on transcriptomics, the value of proteomic analysis is appreciated (Karr, 2007). Complex regulatory routes from posttranslational modifications to protein turnover cannot be studied at the cDNA level, and changes in gene expression 1State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, PR China and 2College of Fisheries, Henan Normal
University, Xinxiang, PR China
Correspondence: Professor C Ke, State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, Fujian Province 361005, PR China.
Received 8 June 2014; revised 12 November 2014; accepted 14 November 2014
Heredity (2015), 1–11 & 2015 Macmillan Publishers Limited All rights reserved 0018-067X/15 www.nature.com/hdy do not necessarily reflect the changes in protein abundance (Xiang et al., 2013). Although transcriptomic analysis has increased our understanding of the heterosis, changes at the mRNA level may not indicate changes at the protein level (Guo et al., 2013).
Proteins are effectors of genetic information and have specific biological functions. Proteins, as performers of gene function, determine phenotypes, which can be thought of as snapshots of genome expression (Jin et al., 2014). Individual protein expression can be treated as inheritance of quantitative characteristics, even without prior information of protein identity, as most often relates to non-model species (Vasemägi and Primmer, 2005). Lately, twodimensional gel electrophoresis (2-DE) has been used to determine correlations between polymorphisms of individual proteins and hybrid vigor for agronomic traits (Xie et al., 2006; Hoecker et al., 2008; Dahal et al., 2012). Proteomic approaches can help characterize molecular phenotypes of hybrids compared with parental species and may identify relevant genetic markers (Guo et al., 2013). Thus proteomics holds promise for sustainable agriculture (Eldakak et al., 2013).