| Rhopilema esculenta is a large edible economic jellyfish mainly distributed in the Bohai Sea,Yellow Sea and East Sea.Jellyfish flavor is delicious and has remarkable medicinal efficacy,which is popular among consumers at home and abroad.In order to meet the market demand of jellyfish,fishermen have been overfishing for a long time,causing a sharp decline in jellyfish natural resources and quality of germplasm.Therefore,it is necessary to evaluate the germplasm quality and nutritional quality of jellyfish.this article through a comprehensive analysis of natural jellyfish in different areas through two aspects of germplasm resources and nutritional quality,it provided theoretical basis for germplasm resources protection,food tracking and production of label of origin.In this study,microsatellite DNA was used as a molecular marker for the evaluation of jellyfish germplasm resources.Base on high-throughput sequencing platform to sequence the transcriptome,the microsatellite markers were isolated and screened.With florescent labeled oligo and capillary electrophoresis,we analysis the germplasm resources of jellyfish form different areas.Then,the quality of jellyfish was evaluated by conbining the result of nutritional components.The detailes is as follows:(1)Charactreization of R.esculenta transcriptome and discovery of microsatellite markersIn order to provide high quality molecular markers for the evaluation of germplasm resources of jellyfish,the jellyfish transcriptome was sequenced using the Illumina Hiseq 2500 transcriptome sequencing plaform,According to the software Trinity assembled to get 149,239 Transcript and 119,874 Unigene.The sequencesare annotated of gene function.Among the 119,874 Unigenes,the largest number of Unigene annotated in the GO database was 18,466(15.4%);the smallest number of Unigene annotated in the NT database was 1,812(1.51%).By comparing and annotating with Nr database,it is concluded that the closest species related to jellyfish are Nematostella vectensis.Using the software MISA to search for SSR loci in all Unigenes,5,088 microsatellite loci were identified.128 microsatellite sequences were randomly selected from the microsatellite library for PCR amplification.101 loci were amplified to obtain a single clear band.After that,30 polymorphic locus were detected in the jellyfish population.The further test in Liaoning population indicated that 30 loci showed polymorphism.The number of alleles were between 4 to 17,the observed heterozygosity(Ho)and expected heterozygosity(He)ranged from 0.0251 to 0.7667 and from 0.0251 to 0.8663 respectively,and the polymorphic information content(PIC)ranged from 0.0248 to 0.7888,of which 15 loci are highly polymorphic,11 loci are moderate polymorphic and 4 loci are low polymorphic.The data show that the microsatellite markers developed in this paper are of high quality and can be used for evaluation of jellyfish germplasm resources and analysis of genetic diversity of jellyfish populations.(2)Evaluation of germplasm resources on four population of R.esculenta by microsatellite markersSynthesizing fluorescent primers of the 30 microsatellite markers,and amplifing by PCR in four geographical populations of Dagang in Tianjin,Panjin in Liaoning,Sheyang in Jiangsu and Yantai in Shandong.Amplification products were separated by capillary electrophoresis.The results showed that the average alleles of four populations were 4.03-6.80,the observed heterozygosity and expected heterozygosity were 0.3906-0.5059 and 0.4353-0.5986,respectively,PIC ranged from 0.3902-0.5497.It indicates that the genetic diversity level of the four populations is was moderate,and the level of genetic diversity is higher than that of tianjin dagang.The order of genetic diversity level was Tianjin > Shandong > Jiangsu > Liaoning.Fst ranged from 0.043 to 0.068,which indicated a moderate level of genetic differentiation among all the populations.(3)Comparative analysis of main nutritional of R.esculenta in different producing areasThe basic nutrient component(protein,fat,ash,polysaccharide content)and amino acid composition of R.esculenta from different producing areas were analyzed.The results showed that: the four producing areas jellyfish have the characteristics of high protein,low fat.The content of crude protein range from 49.95% to 51.96%,the fat content range from 0.39 %to 0.67%,the content of ash and polysaccharide range from 36.02% to 42.09%and from 1.28% to 1.83%.The contents of crude protein,ash,crude fat and polysaccharides of jellyfish among different producing areas were significantly different.The jellyfish in four producing are rich in amino acids,there is no significant difference in amino acid content.The total amount of amino acids is 15.79-18.93 g / 100 g,the content of essential amino acids is 4.54-6.25 g / 100 g,accounting for 29%-33% of total amino acids,and the proportion of pharmacodynamic amino acids is larger,range from 68% to 69%. |
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