Abstract
BackgroundBlunt snout bream (Megalobrama amblycephala) is an herbivorous freshwater fish species native to China and has been recognized as a main aquaculture species in the Chinese freshwater polyculture system with high economic value. Right now, only limited EST resources were available for M. amblycephala. Recent advances in large-scale RNA sequencing provide a fast, cost-effective, and reliable approach to generate large expression datasets for functional genomic analysis, which is especially suitable for non-model species with un-sequenced genomes.Methodology and Principal FindingsUsing 454 pyrosequencing, a total of 1,409,706 high quality reads (total length 577 Mbp) were generated from the normalized cDNA of pooled M. amblycephala individuals. These sequences were assembled into 26,802 contigs and 73,675 singletons. After BLAST searches against the NCBI non-redundant (NR) and UniProt databases with an arbitrary expectation value of E−10, over 40,000 unigenes were functionally annotated and classified using the FunCat functional annotation scheme. A comparative genomics approach revealed a substantial proportion of genes expressed in M. amblycephala tanscriptome to be shared across the genomes of zebrafish, medaka, tetraodon, fugu, stickleback, human, mouse, and chicken, and identified a substantial number of potentially novel M. amblycephala genes. A total number of 4,952 SSRs were found and 116 polymorphic loci have been characterized. A significant number of SNPs (25,697) and indels (23,287) were identified based on specific filter criteria in the M. amblycephala.ConclusionsThis study is the first comprehensive transcriptome analysis for a fish species belonging to the genus Megalobrama. These large EST resources are expected to be valuable for the development of molecular markers, construction of gene-based linkage map, and large-scale expression analysis of M. amblycephala, as well as comparative genome analysis for the genus Megalobrama fish species. The identified SSR and SNP markers will greatly benefit its breeding program and whole genome association studies.
Highlights
Blunt snout bream (Megalobrama amblycephala Yih, 1955), commonly known as Wuchang fish, is an endemic species in China
This study is the first comprehensive transcriptome analysis for a fish species belonging to the genus Megalobrama
These large Expressed Sequence Tag (EST) resources are expected to be valuable for the development of molecular markers, construction of gene-based linkage map, and large-scale expression analysis of M. amblycephala, as well as comparative genome analysis for the genus Megalobrama fish species
Summary
Blunt snout bream (Megalobrama amblycephala Yih, 1955), commonly known as Wuchang fish, is an endemic species in China. M. amblycephala is a species of rayfinned fish in the genus Megalobrama, which includes other three species M. skolkoii, M. hoffmanni and M. pellegrini [3]. Among these four species, M. amblycephala has been widely favored for its delicacy and recognized as a main aquaculture species in the freshwater polyculture system since 1960s in China [4]. Blunt snout bream (Megalobrama amblycephala) is an herbivorous freshwater fish species native to China and has been recognized as a main aquaculture species in the Chinese freshwater polyculture system with high economic value. Recent advances in large-scale RNA sequencing provide a fast, cost-effective, and reliable approach to generate large expression datasets for functional genomic analysis, which is especially suitable for non-model species with un-sequenced genomes
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