Gonadal transcriptome analysis of hybrid triploid loaches (Misgurnus anguillicaudatus) and their diploid and tetraploid parents.

He Zhou,Qi-Zheng Xu,Yin-Qiang Ma,Tian-Yu Ma,Rui Zhang,Zi-Xin Zhuang,Wei Wang,Xiaojuan Cao,Yang Liu,Yi Sui

doi:10.1371/journal.pone.0198179

Abstract

Hybrid triploid loaches (Misgurnus anguillicaudatus) were generated from natural tetraploid and diploid loaches. We studied the gonads of parents and offspring from direct and reciprocal crosses through histological and transcriptome analyses. The triploid offspring had inferior ability to form sperm and egg cells compared with diploid forms. After sequencing the transcriptomes, 655,109,158 clean reads were obtained, and 62,821 unigenes and 178,962 transcripts were assembled. Of these unigenes, 23,189 were annotated in the GO database, 18,525 in the KEGG database and 24,661 in the KOG database. 36 fertility-related genes were found to be differentially expressed between the direct cross (2n × 4n) progenies and their parents, while 53 fertility-related genes between the reciprocal cross (4n × 2n) progenies and their parents. Following protein-protein interaction network analyses, 54 differentially expressed genes, including PLCB4, cyp17a1 and Pla2g4d, were mined, yielding candidate genes involved in the poor fertility of hybrid triploid loaches. This is the first report of transcriptomes of gonads of hybrid triploid loaches and their parents, offering a substantial contribution to sequence resources for this species and providing a deep insight into the molecular mechanism controlling the fertility of hybrid triploid fish.

Highlights

Loach (Misgurnus anguillicaudatus; Cypriniformes; Cobitidae) is one of the endemic fishes of Asia and a common small freshwater fish in China
Triploid fish have the characteristics of fast growth, good meat quality, strong disease resistance, but poor fertility, so its breeding is of great significance [26]
It is generally accepted that triploid fish—being infertile—can transform the energy used in gonadal development into muscle growth, giving them a potential growth advantage

Summary

Introduction

Loach (Misgurnus anguillicaudatus; Cypriniformes; Cobitidae) is one of the endemic fishes of Asia and a common small freshwater fish in China. The loach is distributed in all parts of China. The loach exhibits a range of polyploidy: in addition to diploid, there are natural triploid [1], tetraploid [2,3,4,5] and hexaploid [3] forms in China. This ploidy has received close attention by scholars internationally. Arai et al [4,6,7,8] reported the distribution of natural triploid loach in Japan, but found no natural

Methods

Results

Conclusion