Characterization Of Gonadal Trascriptiomes From Large Yellow Croaker Larimichthys Crocea

Large yellow croaker(Larimichthys crocea)is one of the most economically important marine species in China,which has grown-related sexual dimorphism.However,the knowledge of molecular mechanism of gonadal differentiation in large yellow croaker is still scarce,and the gene expression level during gonadal differentiation is lacking systematic research.In this study,different developmental stages of male and female gonads of large yellow croaker were sequenced by RNA-Seq technology.The main findings are as follows:1.The RNA-Seq was carried out on gonad development of 8 month-old large yellow croaker.The results show that the RNA-Seq produced a total of 250 million raw reads with an average of a 125 bp.Through quality control and splice,77405 transcripts were mapped,and these transcripts average length was 896 bp,including 13342 male higher expressed genes,3573 female higher expressed genes,4713 male specific expression genes and 46 female specific expression genes.The clustering heat map of differential genes displayed that there is a huge difference between the males and the females on gene expression patterns,and there is a good repeatability in the same sex samples.36 sex determination and differentiation related genes were searched in the optimized database,of which 12 genes were identified by RT-PCR,10 genes were consistent with the RNA-Seq results,2 genes were not.2.3 month-old and 18 month-old large yellow croaker gonads were for RNA-Seq,then aligned the processed data at the assembled genome sequences.Combined with the first part of the research,the expression level of the gonad expressed genes during each development of large yellow croaker was analyzed,with screening gonadal sex specific expressed genes.The number of mapped genes were 21,999,21,924 and 19659 in chronological order of gonad development.There were 68 genes specifically expressed in the testis,157 genes specifically expressed in the ovary and 3910 genes co-expressed on 3 month-old gonad development;1959 genes specifically expressed in the testis,45 genes specifically expressed in the ovary and 7480 genes co-expression in the medium-term;and on 18 month-old developmental gonad,there were 976 genes specifically expressed in the testis,140 genes specifically expressed in the ovary and 7233 genes co-expressed.Male’s and female’s data were mixed,the result showed that 13 genes specifically expressed in the testis,eight genes specifically expressed in the ovary and 6773 genes co-expressed.The specific expression genes in different developmental stage of large yellow croaker male and female gonads were used in statistical analysis respectively for moredetailed information about the expression changes of these genes between every two adjacent periods.3.The temporality of the development of large yellow croaker male and female gonads were studied to acquire the expression changes of sex differentiation related genes during the different development stages.In males,the expression level of 2789 genes increased and the expression level of 2944 genes decreased from 3 month-old to 8 month-old;from the mid to 18month-old testicular development,the expression level of 2436 genes increased and the expression level of 2307 genes decreased.In females,from 3 month-old to 8 month-old ovarian development,the expression level of 716 genes increased and the expression level of5061 genes decreased;from the mid to 18 month-old ovarian development,the expression level of 584 genes increased and the expression level of 247 genes decreased.The study had laid the foundation for further studying sex differentiation mechanism in large yellow croaker,as well as providing data and references for fish sex differentiation mechanism and evolutionary studies.