| Apostichopus japonicus has important commercial,nutritional and scientific value.Due to the long-term inbreeding and repeated breeding of the cultured sea cucumber,the growth rate of the sea cucumber is reduced.How to improve the quality of the existing sea cucumber and prevent its quality from falling has become a problem to be solved.Hybridization is one of the effective ways for breeding of aquatic animals.It can not only enrich the genetic structure,enable the combination of different types of parental superior traits,but also acquire new varieties with heterosis,and play a role in the improvement of aquatic animal species and the prevention of germplasm degradation.Great effect.The content of the experiment is divided into two parts.In the first part,in order to explore the intrinsic molecular mechanism of the growth advantage of sea cucumber hybrids,we used the intraspecific hybridization of sea cucumber(R)from Russia's Far East sea area and local sea cucumber(C)from Liaoning,China to select five families(RR,CC,and RC1,RC3,and RC7).Six body tissues:body wall,longitudinal muscle,papillae,tube foot,intestine,respiratory tree of 12-month-old and 13-month-old sea cucumbers were used to perform qPCR on the eight growth trait candidate genes of sea cucumber.Relative quantitative analysis of expression in different tissues and families.The results showed that the expression of EGFR,MAPK7,c-myc,and GDF-8 was higher in other tissues than in other tissues.Fibropellin and FGFR-1 genes had the highest expression levels in their tube foot and intestine,while MAP3K1 had the highest expression levels.There was no significant difference in the expression levels of MAP2K4 and MAP2K4.Compared with Chinese sea cucumber,all three hybrid families showed heterosis of growth.The expression of each gene in the RC3 family was active and the growth was greater than that of RC1,RC7 and CC families.In addition,the mRNA expression of sea cucumbers at 12 months is generally greater than 13 months,which is presumably related to the body mass of sea cucumbers of 12 months of age greater than 13months.In the second part of the experiment,we constructed six transcriptome library of Individual size difference of Apostichopus japonicus,pure lines of Apostichopus japonicus and a hybrid lineage of China and Russian.After transcriptome sequencing,a total of 49.69 Gb clean reads were obtained with the Q30 bases above 90.47%.The data of the samples were compared with those of the sea cucumber reference genomes,and the comparison efficiency ranged from62.30%to 68.73%.For the results,alternative splicing,optimization of gene structure,and excavation of new genes were performed.A total of 5191 novel genes were discovered,among which 2592 genes were annotated.Based on the results of the comparison,gene expression analysis was performed to identify differential genes based on their expression levels in different samples,and functional annotation and enrichment analysis was performed.And heterosis was generated in the little generation,and there were great differences among different individuals of sea cucumber.In the differential gene analysis,1874 differentially expressed genes were screened from the Chinese sea cucumber size difference group;2,591 differential genes were obtained from the differential grouping of sea cucumbers,and 3,006 differential genes were obtained from the differential grouping of sea cucumbers.The GO gene enrichment analysis was performed on the differential genes.The number of differential genes enriched in different GO secondary terms was different in different differential groups.In the KEGG enrichment analysis of the differential genes,three different differential groups were enriched.The number of differential genes is not the same,and the enriched pathways are also different.In the differential grouping of the sea cucumbers,the main enrichment pathways are endoplasmic reticulum protein processing,carbon metabolism,and amino acid biosynthesis;in the differential family of hybrid families,The main enrichment pathways are:fatty acid degradation pathway,fatty acid synthesis pathway,peroxisomes pathway,and folic acid metabolism pathway;and the main enrichment pathways in the Russian Saitama difference grouping are:carbon metabolism pathway,amino acid biosynthesis pathway,glycolysis pathway.The differential genes of F_?VS F_?,R_?VS R_?,and C_?VS C_?were analyzed,and the expression of all 5646 differential genes in F1,R1,and C1 was analyzed for the trend of gene co-expression.The K value was 2.In the analysis results,the expression tendency of 3650 genes in C_?,F_?,and R_?was decreased,and the expression trend of 1996 genes was increased.The growth of sea cucumber requires the co-regulation of a large number of genes.Therefore,the difference in the growth of sea cucumbers in three different families is the result of a large number of genes in the sea cucumber.The study of this experiment can provide an important basis for the optimization of sea cucumber breeding. |
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