Identification and differential expression of piRNAs in the gonads of Amur sturgeon (Acipenser schrenckii).

Lihong Yuan,Jinping Chen,Xiujuan Zhang,Haiying Jiang,Linmiao Li

doi:10.7717/peerj.6709

Abstract

ObjectiveSturgeons are considered living fossils, and have a very high conservation and economic value. Studies on the molecular mechanism of sturgeon gonadal development and sex differentiation would not only aid in understanding vertebrate sex determination but also benefit sturgeon aquaculture. Piwi-interacting RNAs (piRNAs) have been shown to function in germline or gonadal development. In this study, we performed small RNA deep sequencing and microarray hybridization to identify potential sturgeon piRNAs.MethodsMale and female sturgeon gonads were collected and used for small RNA sequencing on an Illumina HiSeq platform with the validation of piRNA expression by microarray chip. The program Bowtie and k-mer scheme were performed to filter small RNA reads and discover potential sturgeon piRNAs. A known piRNA database, the coding sequence (CDS), 5′ and 3′ untranslated region (UTR) database of the A. Schrenckii transcriptome, Gene Ontology (GO) database and KEGG pathway database were searched subsequently to analyze the potential bio-function of sturgeon piRNAs.ResultsA total of 875,679 putative sturgeon piRNAs were obtained, including 93 homologous to known piRNAs and hundreds showing sex-specific and sex-biased expression. Further analysis showed that they are predominant in both the ovaries and testes and those with a sex-specific expression pattern are nearly equally distribution between sexes. This may imply a relevant role in sturgeon gonadal development. KEGG pathway and GO annotation analyses indicated that they may be related to sturgeon reproductive processes.ConclusionOur study provides the first insights into the gonadal piRNAs in a sturgeon species and should serve as a useful resource for further elucidation of the gene regulation involved in the sex differentiation of vertebrates. These results should also facilitate the technological development of early sex identification in sturgeon aquaculture.

Highlights

Sturgeons are referred to as living fossils and have considerable value in aquaculture as sturgeon eggs (Bemis, Findeis & Grande, 1997; Ludwig, 2008)
Our study revealed a large number of sturgeon-specific Piwi-interacting RNAs (piRNAs) and provided candidates for further study of sturgeon gonadal development
We have identified a large number of potential novel piRNAs and provided the first description of the presence of piRNAs with likely roles in sturgeon gonadal development and sex differentiation

Summary

Introduction

Sturgeons (order: Acipenseriformes, infraclass: Chondrostei) are referred to as living fossils and have considerable value in aquaculture as sturgeon eggs (caviar) (Bemis, Findeis & Grande, 1997; Ludwig, 2008). Sturgeons contain 25 caviar-producing species, 17 of which are members of the Acipenser genus (Bemis, Findeis & Grande, 1997). Due to the huge profits associated with the sale of sturgeon caviar, over-exploitation of wild stocks occurred worldwide throughout the 20th century, and major sturgeon fisheries are in decline (Pikitch et al, 2005). Given the decline of wild stocks and conservation, great efforts have been made to develop commercial sturgeon aquaculture to meet the demand for caviar, originally in Europe and North America but more recently in Russia, Iran and China (Raymakers & Hoover, 2010; Wei et al, 2011). It is estimated that approximately 50% of the caviar in trade is from farmed stocks (Bronzi, Rosenthal & Gessner, 2011)

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