Cloning And Application Of The Full-length Sequences Of The Ribosomal Gene Cluster Unit Of Ulva Prolifera Which Was The Main Species Of The Green Tide In The Yellow Sea Of China

Ulva prolifera is a large marine green algal belonging to the family of Ulvaceae,widely distributed in all the world's oceans.In 2008,the largest green tide in the world was erupted in the Yellow Sea in China.The green tide not only brought tremendous impact on the tourism,aquaculture industry and people's life in coastal areas of Shandong Province and Jiangsu Province,but also greatly negative impact on the local ecology environment.The study found that the direct cause of the formation of a green tide in the Yellow Sea in China is the result of the outbreak of major marine green algae dominated by U.prolifera,which are floating on the sea surface.After the occurrence of the Green Tide,although the relevant departments took some urgent measures to deal with it,the effect was not obvious,and the green tide will reoccur after a year.In order to reduce the disasters caused by the green tide,it is necessary to study the biology of its main species U.prolifera.In this paper,genomic DNA of U.prolifera was extracted by using plant genomic DNA extraction kit.The full-length sequence of ribosomal gene cluster unit of U.prolifera in the Yellow Sea of China was amplified by PCR,sequenced and sequenced.The results showed that the full-length sequence of ribosomal gene cluster unit of the U.prolifera was 8948 bp,of which 18 S r DNA 1760 bp,28 S r DNA 3259 bp,ITS1 205 bp,5.8S r DNA 160 bp,ITS2 176 bp and IGS 3388 bp.The base composition of each part of the sequence analysis found that ITS and IGS sequences have obvious preference for cytosine,and 18 S r DNA and 28 S r DNA sequences have obviouspreference for guanine.The GC content of the full-length sequence of U.prolifera gene cluster was 54.12%.The GC content of ITS and IGS sequences was higher than the GC content of the conserved sequence,indicating that the internal transcribed spacer sequences and intergenic sequences had higher mutation rate and faster evolution rate than the conserved sequences.In addition,a large number of simple direct repeat sequences,tandem repeats,short symmetric sequences and palindromic sequences were found in IGS sequences.IGS sequences were used to classify four different kinds of Ulva species from nine samples.According to the results of IGS sequence analysis,it was found that the length of IGS sequences of different species of Ulva species was quite different.The length of IGS sequences was similar among U.compressa,U.flexuosa and U.prolifera.IGS sequence similarity analysis and genetic distance analysis showed that U.prolifera and U.flexuosa have the largest similarity and the smallest genetic distance,the similarity between the two sequences is 49.4%,the genetic distance is 1.031 ~ 1.082;U.compressa and U.flexuosa have the largest similarity and the smallest genetic distance,the similarity between the two sequences is 73.7 ~ 74.0%,the genetic distance is 0.098.Among the phylogenetic trees constructed,although there are some differences between IGS phylogenetic tree topology and ITS phylogenetic tree,four kinds of Ulva are clustered into different independent branches.So,we know that there is a big gene sequence difference in vary Ulva species,and the IGS sequence can be used for species identification and classification in green algae.Since IGS sequence can be used to study the genetic relationship of the same species in different geography groups,this paper studies the origin of U.prolifera by partial IGS sequences.After comparative analysis,it was found that the IGS sequences of the green-tide species floating on the Yellow Sea were identical,which means that they are the same species of the same type.and the IGS sequences of floating U.prolifera samples were similar to those of the Boao(BA)of Hainan province,Wendeng(WD)and Rushan(RS)of Shandong province,and the Pyropia farming raft(PFR)of Jiangsu province,which indicating that the source of green tide in the YellowSea is closely related to the U.prolifera in Shandong,the U.prolifera in Jiangsu province and the U.prolifera in Hainan province.In addition,different types of U.plifera were found in Haiyang of Shandong Province,Dafeng of Jiangsu Province and Xiangshan of Zhejiang Province.The results of this study provide new evidence and ideas for the research of origin of green tide.