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

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.

Transcriptome Analysis of Maternal Gene Transcripts in Unfertilized Eggs of Misgurnus anguillicaudatus and Identification of Immune-Related Maternal Genes

“…Although the N50 statistic is not entirely appropriate for de novo transcriptome assemblies, it is still a traditionally valuable measurement for the assessment of continuity in transcriptome assembly [33,34]. Thus, the N50 value (1533 bp) of our transcriptome assembly was comparable to those obtained for published de novo transcriptomes of M. anguillicaudatus [21,[35][36][37]. The detailed length distribution of de novo assembled transcriptome is shown in Figure S1.…”

“…However, in contrast to the rather rich studies on immune factors, a study that builds a comprehensive understanding of maternal immune gene transcripts in fish species remains limited. Recently, next-generation sequencing (NGS) technologies have revolutionized our ability to analyze the dynamic gene transcripts in a specific cell, tissue, or organism at a given developmental stage [11,[19][20][21]. As the analysis of massive quantities of genes has allowed gene discovery and expression profiling, recent transcriptome data for several fishes have provided notable insights into the distinctive features in oocyte development and early embryonic development [19,[22][23][24][25].…”

Incidence of skeletal deformities in induced triploid rainbow trout Oncorhynchus mykiss (Walbaum, 1792)

“…Suppression of the second meiotic division was observed in poor-quality post-ovulatory ageing oocytes (Aegerter & Jalabert 2004;Flajšhans et al 2007). Triploid individuals can be obtained by mating tetraploid and diploid individuals, as reported in pond loach (Arai & Fujimoto 2013;Zhou et al 2018), rainbow trout (Chourrout et al 1986;Blanc et al 1987;Myers & Hershberger 1991;Quillet et al 1988) and Iberian minnow (Alves et al 2001), or by dispermic fertilization of an haploid egg (Ueda et al 1986;Grunina et al 2006). Moreover, exposure of activated eggs to chemical (colchicine, ether, deuterium oxide and specific enzyme inhibitors) or physical (sub-lethal temperature or high hydrostatic pressure HHP) shock shortly after fertilization also results in the development of triploid specimens (Piferrer et al 2009).…”

Formation of autotriploid Carassius auratus and its fertility-related genes analysis

“…In addition, a previous study reports that the triploid can channel the energy required for gonad maturation to somatic growth, causing rapid growth rates compared with their diploid counterparts [ 16 ]. However, a different study reported that triploid fish can produce normal gametes [ 17 ]. In our previous study, Carassius auratus red var.…”

“…Studies on Takifugu rubripes reported that sex-related genes play an important role at early sex differentiation stage [ 22 ]. Gonadal transcriptome profiling of triploid hybrid loaches ( Misgurnus anguillicaudatus ) and their diploid and tetraploid parents showed key genes implicated in low hybrid triploid fertility [ 17 ]. A study on Thunnus maccoyii reported sex and gonad-development-related genes in the gonads of Southern bluefin tuna through RNA-Seq [ 23 ].…”