De novo transcriptome assembly of four organs of Collichthys lucidus and identification of genes involved in sex determination and reproduction

Abstract

Background Spinyhead croaker (Collichthys lucidus) is an important kind of fish for commercial fishery because of its delicious meat and abundant resource. However, the resource has been declining with the overfishing and environmental disruption. Unfortunately, the mechanism of sex determination and reproduction in Collichthys lucidus is still confusing, which has largely hindered molecular regulation and reproduction studies. Results Based on transcripts sequencing in brain, liver, ovary and testis, a de novo transcriptome assembly of Collichthys lucidus was performed. Totally, 131,168 non-redundant unigenes with an average length of 644 bp and an N50 value of 1033 bp, among which 2,143, 304, 333 and 556 were found specifically expressing in brain, liver, ovary and testis, respectively. Importantly, 1288 genes were differently expressed between ovary and testis, including 442 up- and 846 down-regulated in ovary. The differently expressed genes were involved in function of sexual reproduction, sex differentiation, development of primary male sexual characteristics, female gamete generation, and male sex differentiation. HYAL and SYCP3, two genes which were reported to play dominant roles in reproduction, may regulated the key of fertilization and meiosis in Collichthys lucidus. Meanwhile, 35,476 simple sequence repeats (SSRs) were identified, which would contribute to further genetic and mechanism researches. Conclusions The studies of genetic information, molecular regulation and reproduction of Collichthys lucidus would be expand due to the sequencing and de novo assembling on the transcripts of major organs. In addition, the identification of candidate genes involved in reproduction will be useful for protecting the resource of Collichthys lucidus.