Abstract
Flathead gray mullet (Mugil cephalus) is a cosmopolitan mugilid species popular in fishery and aquaculture with an economic preference for all-female population. However, it displays neither sexual dimorphisms nor heteromorphic sex chromosomes. We have previously presented a microsatellite-based linkage map for this species locating a single sex determination region (SDR) on linkage group 9 (LG9) with evidence for XX/XY sex determination (SD) mechanism. In this work, we refine the critical SDR on LG9, and propose positional- and functional- candidate genes for SD. To elucidate the genetic mechanism of SD, we assembled and compared male and female genomic sequences of 19 syntenic genes within the putative SDR on mullet’s LG9, based on orthology to tilapia’s LG8 (tLG8) physical map. A total of 25 sequence-based markers in 12 genes were developed. For all markers, we observed association with sex in at least one of the two analyzed M. cephalus full-sib families, but not in the wild-type population. Recombination events were inferred within families thus setting the SDR boundaries to a region orthologous to ∼0.9 Mbp with 27 genes on tLG8. As the sexual phenotype is evident only in adults, larvae were assigned into two putative sex-groups according to their paternal haplotypes, following a model of XY/XX SD-system. A total of 107 sex-biased differentially expressed genes in larvae were observed, of which 51 were mapped to tLG8 (48% enrichment), as compared to 5% in random control. Furthermore, 23 of the 107 genes displayed sex-specific expression; and 22 of these genes were positioned to tLG8, indicating 96% enrichment. Of the 27 SDR genes, BCCIP, DHX32A, DOCK1, and FSHR (GTH-RI) are suggested as positional and functional gene candidates for SD.
Highlights
Teleostei is a large infraclass including about 34,200 fish species1
MSH2 was found in O. niloticus but not in D. labrax LG1
Nineteen genes on tilapia’s LG8 (tLG8) that are colored in red were assembled from M. cephalus male and female DNA sequencing data
Summary
Teleostei is a large infraclass including about 34,200 fish species1 It presents diversity of mechanisms for sex determination (SD), which involve environmental and social effects, genetic and epigenetic influences (Devlin and Nagahama, 2002; Baroiller et al, 2009; Martinez et al, 2014; Mei and Gui, 2015). Among different animal species only several genes have been established as initiators of the SD cascade that results in the two alternative forms of female and male Such master genes of SD frequently have truncated copies of the original genes i.e., AMH, DMRT1, SOX3, IRF9, AMHR2, and GSDF (Li and Gui, 2018; Matsuda, 2018). Fine mapping of SD region (SDR) has been pursued in a number of fish species; e.g., Takifugu niphobles, Channa argus, Seriola dorsalis, Poecilia reticulata and most of tilapia species; none of the above six master genes of SD have been detected in their SDR (Gammerdinger et al, 2016; Ieda et al, 2018; Purcell et al, 2018; Dor et al, 2019; Wang et al, 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
