中国明对虾核糖体ITS1序列分析及其在对虾科系统分析中的应用

The First Ribosomal Internal Transcribed Spacer of Fenneropenaeus chinensis and Its Applicability as a Marker for Phylogenetic Analysis

对采自不同群体的5个中国明对虾个体的核糖体RNA转录单元内间隔区1（ITS1）序列特点进行分析,并利用GeneBank数据库中已有的对虾科（Penaeidae）ITS1同源序列对对虾科虾类进行系统分析,探讨ITS1序列在对虾科系统及演化中的应用。结果表明,中国明对虾ITS1序列在个体间和个体内都表现出长度多态性,序列长度范围为637-652 bp,这种长度多态性主要是由于微卫星DNA简单重复序列的重复次数不同所造成。在中国明对虾ITS1序列中发现8个微卫星位点,根据目前已知的12种对虾的ITS1序列,发现某些微卫星位点只存于1种对虾中,如（CAGC）2-4只存在于中国明对虾中,（CGGA）4-9只存在于斑节对虾中,（GCGA）4只存在于短沟对虾中。利用ITS1序列对12种对虾进行的系统分析表明,12种对虾分为4个类群,同种的不同个体,同属的不同种各自聚支,与形态分类比较吻合。对虾科属间遗传距离范围为0.313-0.977,平均值为0.633,远高于用线粒体基因片段得出的属间的遗传距离,支持将原对虾属的6个亚属提升为属的观点。

The ribosomal DNA internal transcribed spacer 1（ITS1） of Fenneropenaeus chinensis was cloned and sequenced.The objective of the present study was to estimate phylogenies and explore the feasibility of using ITS1 as a molecular marker for studying the interspecific and intraspecific genetic variations among penaeid shrimps.Inter-and intraindividual polymorphisms of ITS1 were clearly observed in F.chinensis.The length of the ITS1 ranged from 637 to 652 bp,with a GC content of 66.9%.Repeats of microsatellite loci of ITS1 play an important role in length heteroplasmy at both between-and within-individual levels in this species.Eight microsatellite loci were found in the ITS1 sequence of F.chinensis.According to existing data,some microsatellites were found in only one species,（CAGC）2-4 in F.chinensis,（GCGA）4 in P.semisalcatus and（CGGA）4-9 in P.monodon.The DNA data of the penaeid shrimps were processed in neighbor-joining（NJ） methods to build phylogenetic relationships within the family of Penaeidae.According to the NJ tree,different individuals of the same species,different species of the same genera were grouped together,in consistence with the morphological taxonomy.The genetic distances among different genera ranged from 0.313 to 0.977 and the average was 0.633,exceeding those estimated with COI and partial 16S rRNA gene sequences,and being therefore larger than the value among subgenera.The results of the present study indicated that Fenneropenaeus,Litopenaeus,Farfanatepenaeus,Marsupenaeus and Penaeus are at a higher phylogenetic level than subgenus,which supports the opinion of the elevation of phylogenetic status of the four subgenera to genus level.These results show that ITS1 is highly divergent among different penaeid shrimps and could be an appropriate marker for molecular systematic studies at the species levels,although the presence of intragenomic variation needs to be taken into consideration.