Transcriptomics Of Sex Dimorphism In The Cynoglossus Semilaevis

Fish individual growth traits is an important economic character,which is closely linked with the fish farming production in aquatic products with a high attention in the basic research.Growth and reproduction are the most basic characteristics of organisms.The growth of vertebrates is regulated by the "hypothalamus-pituitary-liver" axis.Vertebrate reproduction is mainly regulated by the "brain/hypothalamic-pituitary-gonadal" axis.Growth and reproduction are closely related but different.On the one hand,the development of gonads is closely related to the development of the body during development.Fish growth hormone receptors,insulin-like growth factors are expressed in various tissues including the gonads.This means that the growth hormone secreted by the pituitary gland can affect the growth of the body and the development of the gonad,thereby coordinating the growth and development of both.On the other hand,during the oviposition cycle of females,the growth of the ovary is not related to the growth of the body.The gonad differentiation is accompanied by cell differentiation and tissue growth.Therefore,growth hormone,growth hormone receptors,insulin-like growth factor growth regulatory axis and some local regulators are also present in the gonad,which can accurately regulate ovarian development and maturation.The growth of fish individual performance is the body growth and reproduction regulation axis interaction,mutual influence the effects of the mechanism of balance.The Chinese tongue sole(Cynoglossus semilaevis)belongs to Pleuronectiformes,Cynoglossidae,and Cynoglossus.It is mainly distributed in the coastal region of China's Yellow Sea and Bohai Sea.It is a unique rare marine fish cultured in China because of its chromosomedetermining type of ZZ/ZW,and the difference in male and female growth,the growth rate of female fish is 2-4 times than that of males.In recent years,the Chinese tongue sole(Cynoglossus semilaevis)has become an important fish to study in the sex determination mechanism of fish.The genome-wide fine maps of the Chinese tongue sole(Cynoglossus semilaevis)have been mapped and the Z and W chromosome structures have been mapped out to reveal the mechanism of the evolution of chromosomes and the apparent regulatory mechanism of sexual reversion.However,the current research on the growth difference is limited to several important factors in growth axis of the Chinese tongue sole(Cynoglossus semilaevis)such as growth hormone,growth hormone receptor,growth hormone releasing hormone,insulin-like growth factor and their expression of IGF-IR and in pituitary adenylyl cyclase were studied at different developmental stages and between different sexes.Studies on the mechanism of interaction between growth regulatory axis and reproductive regulatory axis of the Chinese tongue sole(Cynoglossus semilaevis)have not been reported.This paper reviews the recent research on the regulation of growth hormone by neuroendocrine factor and reproductive endocrine regulation axis.In the experiment,15 male and 15 female fish of two years old were used,and four tissues including brain,pituitary,liver,and gonads were subjected to RNA extraction and transcriptome sequencing.Each sequencing library yielded 37,733,991 high-quality clean reads,four tissues in the male and female groups,and 806,1482,818 and 14,695 differentially expressed genes in the brain,pituitary,liver and gonads(differentiation?2 and q< 0.05).The activity of nucleic acid-binding transcription factors,G protein-coupled receptor activity,MAPK signaling pathway,steroid biosynthesis,and neuroactive ligandreceptor interactions are all possible related to gender growth differences through GO functional enrichment and KEGG pathway enrichment analysis.In addition,a weighted gene co-expression network analysis showed that there were two modules(yellowgreen and salmon4)showing a significant positive correlation between male and female individuals.A series of key genes were screened from the network maps drawn from these two modules,including nipped-B-like protein A(nipbla),the transcriptional activator Pur-beta-like(purb),and BDNF/NT-3 growth factors,Receptor(ntrk2)and so on.Twenty differentially expressed genes in the transcriptome were selected(araf,egr1,egr4,gdf8,igfbp5,mapk5,ntrk2,lepr,lrp3,purb,fos,gna12,jun,lrp1 b,lrp2,lrpap1,pdgfra,pias2,sos1,un),and high-throughput sequencing data were verified by quantitative PCR experiments.The expression trends of the various significant differentially expressed genes were basically consistent with the sequencing results.Semi-quantitative PCR,real-time fluorescence quantitative PCR and in situ hybridization were used to study the expression patterns of two key genes: nipbla and purb in the tissues of both sexes.Based on the above experimental studies,the study of these regulatory networks and the subsequent specific functions of key genes will further enhance our in-depth understanding of the intrinsic molecular mechanisms underlying the differential growth of male and female individuals in fish.