Sequencing And Analysis Of Nuclear RDNA Internal Transcribed Spacers(ITS-1) Of Macrobrachium Nipponense

Macrobrachium nipponense, also named river prawn, belongs to Arthopoda,Crustacean, Decapoda, Palaemonide, Macrobrachium in taxonomy. Macrobrachiumnipponense widely distributed in China and characterized by rapid growth, strongreproduction and extensive adaptability was an important breed in freshwater aquacultureand one of the most productive species. Macrobrachium nipponense is one of importantfreshwater species for aquaculture in China. However, serious retrogression of economictraits appeared recently in Macrobrachium nipponense culture, such as prematuration, smallsize, low marketing rate weak disease-resistance which greatly lowered its profits.In orderto realize the sustainable development of Macrobrachium nipponense culture, it's necessaryto carry out resources protection and genetic improvement and investigation on geneticbackground and genetic divergence is the basis.Nuclear rDNA Internal Transcribed spacer(ITS) are composed of ITS-1 fragmentbetween 18S and 5.8S rRNA and ITS-2 fragment between 5.8S and 28S rRNA. Lessselective pressure and extensive variation were found on ITS due to its absence in matureribosome rDNA. On the other hand, primers were designed conveniently because of highconservation of 18S, 5.8S and 28S rRNA. Analysis on genetic divergences betweenindividuals and populations and genetic background were carried out by using the extensivevariation of ITS sequences.In this paper, ITS technology was applied to genetic research of Macrobrachiumnipponense. Internal Transcribed Spacer (ITS-1) region of nuclear rDNA fromMacrobrachium nipponense were amplified by PCR with suitable primers and a clearamplification band appeared in electrophoresis. ITS-1 sequence with 1763 bp in size wasproduced with DNAStar software after T-carrier connection, clone and sequencing of thepurified PCR products. ITS-1 sequence above was the longest one among reported ITS-1sequences so far. The contents of A, T, G and C were 29.92%, 27.71%, 28.36% and 14.26%respectively. G+C content was 42.44%, and A+T content was higher than G+C content.Repeat sequences were observed in ITS-1 of Macrobrachium nipponense.TTTATTAAAGAAGAAA repeated six times and (GA)_n(n=5, 6, 5 respectively) appearedin three regions of ITS-1. Sequence comparison revealed there were 13 bases of transitions,9 of transversions, 4 of deletions and 2 of insertions.Our research filled in the gap in ITS technique application and broadended genetic background knowledge of Macrobrachium nipponense. The results were helpful to geneticbreeding of Macrobrachium nipponense.