蜜蜂全基因组中微卫星的丰度及其分布

查找出蜜蜂基因组中由1～6个碱基重复单元组成的简单序列重复,分析蜜蜂基因组中微卫星的分布频率,并比较其在各染色体中的分布频率。微卫星在蜜蜂基因组中的分布频率为1/0·804kb,其中二碱基重复序列占26·86%,是最丰富的重复单元,而六、一、三、四、五碱基重复单元序列分别占24·74%,22·19%,13·65%,10·98%,2·59%。同时发现富含A和T碱基的微卫星占主导地位,富含G和C碱基的微卫星数量较少。第4,1,3条染色体微卫星分布频率较高,而第11,14,12条染色体微卫星分布频率较低。     

桉树EST序列中微卫星含量及相关特征

通过对桉树属(Eucalyptus)的10 000条EST序列进行分析, 在其中的1 499条序列上共发现1 775个微卫星重复序列。含有微卫星的EST序列约占序列总数的15%。此外, 还发现桉树EST序列所含微卫星长度的变异速率与重复单元长度呈负相关; 微卫星的丰度与重复单元长度也呈负相关(三碱基重复微卫星除外)。在桉树EST序列中, 重复单元长度为三碱基的微卫星最为丰富。三碱基重复单元微卫星的过度富集可能是由于遗传密码选择所致。在微卫星的丰度及长度变异方面, 桉树EST序列与杨树(Populus trichocarpa)基因组注释的转录序列随重复单元长度的变化呈现出相同的规律, 但桉树EST序列中微卫星频率及三碱基重复微卫星的含量显著偏低, 推测含微卫星的基因表达丰度极有可能低于不含微卫星的基因。通过对发现的所有微卫星位点进行引物设计, 并对设计的引物进行PCR检测, 结果表明所设计的引物具有极高的扩增成功率。     

桉树EST序列中微卫星含量及相关特征

通过对桉树属（Eucalyptus）的10000条EST序列进行分析,在其中的1499条序列上共发现1775个微卫星重复序列。含有微卫星的EST序列约占序列总数的15%。此外,还发现桉树EST序列所含微卫星长度的变异速率与重复单元长度呈负相关;微卫星的丰度与重复单元长度也呈负相关（三碱基重复微卫星除外）。在桉树EST序列中,重复单元长度为三碱基的微卫星最为丰富。三碱基重复单元微卫星的过度富集可能是由于遗传密码选择所致。在微卫星的丰度及长度变异方面,桉树EST序列与杨树（Populus trichocarpa）基因组注释的转录序列随重复单元长度的变化呈现出相同的规律,但桉树EST序列中微卫星频率及三碱基重复微卫星的含量显著偏低,推测含微卫星的基因表达丰度极有可能低于不含微卫星的基因。通过对发现的所有微卫星位点进行引物设计,并对设计的引物进行PCR检测,结果表明所设计的引物具有极高的扩增成功率。     

红原鸡全基因组中微卫星分布规律研究

本文对红原鸡Gallus gallus全基因组中微卫星数量及分布规律进行了分析,查找到l～6个碱基重复类型的微卫星序列共282728个,约占全基因组序列(1.1Gb)的0.49%,分布频率为1/3.89kb,微卫星序列的长度主要在12～70个碱基长度范围内。第1、2、3条染色体上微卫星分布频率较高,而32号染色体上无微卫星分布。不同类型微卫星中,单碱基重复类型数目最多,为184192个,占总数的65.1%;其次是四、二、三、五、六碱基重复单元序列,分别占到总数的12.8%、9.7%、7.2%、4.6%、0.8%。T、A、AT、GTTT、AAAC、G、C、ATTT、AC、GT、AAAT、ATT、AAC、AAT、GTT、AG、CT、CTTT、AAAG、GTTTT、AAACA、AAGG、CCTT是红原鸡基因组中最主要的微卫星重复类型。本研究为红原鸡微卫星标记的分离筛选、遗传多样性的研究以及不同物种微卫星的比较分析奠定了基础。     

荒漠昆虫小胸鳖甲转录组微卫星的生物信息学分析

位于蛋白质编码区及非编码区(可转录区)的微卫星是常用的一种功能分子标记。本研究以荒漠拟步甲科昆虫小胸鳖甲(Microdera punctipennis)为材料,从其转录组数据库中筛选出由1~6个碱基单元组成的简单序列重复进行分析,并对其微卫星的丰度和特征进行描述。研究显示,小胸鳖甲转录组中微卫星的分布频率为7.94%。其中,单碱基重复序列占微卫星的47.17%,是最丰富的重复序列;其次为3碱基重复序列,占39.81%,而2、4、5、6碱基重复序列分别占10.94%、0.90%、0.88%和0.29%。将小胸鳖甲转录本与同为拟步甲科的赤拟谷盗(Tribolium castaneum)编码序列进行比对,分析同源序列微卫星基元(motif)发现,二者蛋白质编码区微卫星具有高度物种特异性。对小胸鳖甲低温响应转录本和总转录本进行微卫星基元和不同长度微卫星重复次数的比较发现,它们之间没有显著性差异。对含有微卫星的冷响应基因进行基因本体论(gene ontology,GO)分析,发现主要富集到生物学过程、分子功能和细胞组分3个类群。     

蚊子全基因组中微卫星的丰度及其分布

微卫星是近年大力开发的一种遗传标记,为推进按蚊遗传学相关研究,对按蚊全基因组中由 1~6 个碱基重复单元组成的简单序列重复 ( 微卫星 ) 进行了分析 . 进而对其微卫星的丰度和分布进行了比较分析,也比较了染色体各个区域 ( 外显子、内含子和基因间隔区 ) 之间的分布差异 . 微卫星在按蚊基因组中的比例约占 2.14% ,其中 X 染色体拥有微卫星的密度最大 . 对按蚊基因组中微卫星丰度而言, A 碱基和 C 碱基重复在基因组中丰度相似, AC 单元的丰度是 AG 单元的两倍多,然而 AT 和 CG 单元非常稀少;对于三四碱基而言, AGC, AAAC 和 AAAT 单元最为丰富, ACG, ACT, AGG, CCG, ATGC, CCCG, ACTG, AACT, ACGT, AGAT, CCGG, ACCT 和 AGCT 单元等均很稀少,而一些五碱基重复,在某条甚至某几条染色体中均未分布 . 除两碱基重复单元在 2L 的外显子区域丰度较高外,其他重复单元均在内含子和基因间隔区丰富 . 进一步分析显示,微卫星在每条染色体两臂的丰度和分布存在着很多的相似性 .     

大熊猫和北极熊基因组微卫星分布特征比较分析

本研究比较分析了大熊猫和北极熊全基因组序列中的1~6碱基重复的完美型微卫星序列的分布特征,通过微卫星序列搜索和统计软件MSDB分析分别得到855 018和936 238个微卫星序列,其长度总和分别是14 919 240 bp和18 434 348 bp;分别占基因组大小的0.64%和0.79%,大熊猫和北极熊基因组总丰度分别是371.8个/Mb和405.6个/Mb,二者基因组中微卫星都是单碱基重复的最多,其次是二碱基、四碱基、三碱基和五碱基,六碱基重复类型的数量最少。大熊猫和北极熊含量最丰富的重复拷贝类别主要有A、AC、AG、AAAT、AAAG、AT和C等。本研究为后续开发和筛选大量高质量的熊科物种微卫星标记提供了数据支持。     

红尾蚺和原矛头蝮基因组微卫星分布特征比较分析

本研究分析比较了红尾蚺Boa constrictor和原矛头蝮Protobothrops mucrosquamatus基因组微卫星的分布特征,通过MISA分别鉴定出398 860个和422 364个微卫星,其长度分别为8 550 741 bp和12 243 226 bp,分别占基因组序列总长度的0.59%和0.73%,在各自基因组中的丰度分别为275.46个/Mbp和252.33个/Mbp。红尾蚺基因组中单碱基重复类型微卫星最多,其次是四碱基、二碱基、三碱基、五碱基和六碱基,最丰富的5种微卫星类型是A、AC、AAAT、AG、AAT;原矛头蝮基因组中单碱基重复类型微卫星最多,其次是三碱基、四碱基、二碱基、五碱基和六碱基,最丰富的5种微卫星类型是A、AAT、AC、C、AAAT。红尾蚺和原矛头蝮微卫星在基因组不同区域丰度不同,基因间区丰度最高,其次是内含子和外显子,编码区微卫星丰度最低,表明编码区微卫星受到的选择压力最大。红尾蚺和原矛头蝮在基因中微卫星丰度分布的位置特征相似,即微卫星在基因上下游500 bp丰度最高,在内含子次之,在外显子最低。红尾蚺和原矛头蝮基因编码区所有6种重复类型微卫星中,三碱基重复类型占绝对优势。红尾蚺和原矛头蝮基因组中含有微卫星的编码序列分别有1 480条和1 397条,被GO注释的分别有736条和733条。它们的GO功能归类结果类似,但是与其他物种相比存在种系差异。本研究结果为后续开发这2种蛇的高质量微卫星标记提供了方便,也为进一步探索这些微卫星在它们基因组中的生物学功能提供了有意义的基础数据。     

林麝全基因组微卫星分布规律研究

林麝Moschus berezovskii是中国重要的资源动物,也是国家Ⅰ级重点保护野生动物。本研究使用生物信息学方法,分析林麝全基因组中完美型微卫星的分布特征。在林麝2.53 Gb的基因组序列中,共搜索到665 524个完美型微卫星,总长度为11 517 784 bp,占基因组序列总长度的0.42%,总丰度为244个/Mb。林麝基因组中,单碱基微卫星序列数量最多,为221 058个,约占总微卫星数的33.22%,丰度为81.05个/Mb,然后依次为二碱基、五碱基、三碱基、四碱基、六碱基重复类型微卫星。林麝基因组中数目最多的10种微卫星类别依次为:A、AACTG、AGC、AC、AT、AG、AAAT、AAC、AAT和AAAC,占所有基因组微卫星的93.2%,表现出明显的A、T偏好。林麝基因组微卫星序列分布研究表明,其在外显子(2 530个)上的分布数量远低于内含子(200 906个)和基因间隔区(454 596个),与前人关于微卫星在非编码区的分布多于编码区的结论一致。本研究为深入研究林麝基因组特征及筛选更多优良微卫星标记提供了基础数据。     

大蹄蝠全基因组微卫星分布特征分析

脊椎动物基因组含有丰富的微卫星信息。本研究对翼手目动物中的大蹄蝠全基因组及其基因的微卫星分布特征进行分析,并对含有微卫星编码序列的基因进行注释分析。结果表明,大蹄蝠全基因组大小为2.24 Gb,共含有497 883个微卫星,其中,数量和比例最多的是单碱基和二碱基重复类型,分别有173 953个(34.94%)和222 591个(44.71%),相对丰度分别为77.78 loci/Mb和99.52 loci/Mb。微卫星数量从单碱基重复到六碱基重复单元最多的类型分别为(A)n、(AC)n、(TAT)n、(TTTA)n、(AACAA)n和(TATCTA)n,比例分别为95.14%、55.25%、38.41%、22.17%、48.68%和20.30%。不同基因区和基因间区的数量及丰度不同,其中基因间区的微卫星数量及其丰度最大,分别为322 666个和2 541.57 loci/Mb,编码区的微卫星数量及其丰度最小,分别为1 461个和461.98 loci/Mb。基因间区和全基因组的微卫星的分布特征相似。编码区最多的微卫星类型为三碱基重复单元,外显子最多的微卫星类型为单碱基、二碱基和三碱基重...     

蜜蜂EST中的微卫星分析

为加速分子标记在蜜蜂遗传、进化与行为等方面的利用,分析了简单重复序列(Simple Sequence Repeats,SSRs)在蜜蜂EST中的分布频率与密度。所分析的蜜蜂EST数据集包含15869条序列,总长为7．9Mb。结果显示,蜜蜂ESTs中SSRs的频率为1／0．52kb,其中6碱基重复基序占总SSRs的45．0％,是最丰富的重复单元,而2、1、3、4与5碱基重复基序分别占总SSRs的17．9％、14．1％、11．6％、9．2％和2．2％。同时,在各种SSRs重复单元中,富含A碱基的重复单元占据优势地位,如：A、AT、AG、AC、AAT、AAG、AAC、AAAT、AAAG、AAAAG、AAAAT、AATAT、AAAAAG和AAAAAT重复基序,而富含G碱基的重复单元在基因编码区中含量较低。进一步分析显示：蜜蜂SSRs在冗余与非冗余EST数据集中的分布频率与密度相似,仅存在极小的偏差,表明可从现有的部分ESTs数据中方便地获取有效的微卫星标记。     

Genome-wide identification and characterization of simple sequence repeat loci in grape phylloxera, Daktulosphaira vitifoliae

A genome-wide sequence search was conducted to identify simple sequence repeat (SSR) loci in phylloxera, Daktulosphaira vitifoliae, a major grape pest throughout the world. Collectively, 1524 SSR loci containing mono-, di-, tri-, tetra-, penta-, and hexanucleotide motifs were identified. Among them, trinucleotide repeats were the most abundant in the phylloxera genome (34.4%), followed by hexanucleotide (20.4%) and dinucleotide (19.6%) repeats. Mono-, tetra- and pentanucleotide repeats were found at a frequency of 1.3, 11.2 and 12.9%, respectively. The abundance and inherent variations in SSRs provide valuable information for developing molecular markers. The high levels of allelic variation and codominant features of SSRs make this marker system a useful tool for genotyping, diversity assessment and population genetic studies of reproductive characteristics of phylloxera in agricultural and natural populations.     

Analysis of simple sequence repeats (SSRs)dynamics in fungus Fusarium graminearum

The abundance and inherent potential for variations in simple sequence repeats (SSRs) or microsatellites resulted in valuable source for genetic markers in eukaryotes. We describe the organization and abundance of SSRs in fungus Fusarium graminearum (causative agent for Fusarium head blight or head scab of wheat). We identified 1705 SSRs of various nucleotide repeat motifs in the sequence database of F. graminearum. It is observed that mononucleotide repeats (62%) were most abundant followed by di- (20%) and trinucleotide repeats (14%). It is noted that tetra-, penta- and hexanucleotide repeats accounted for only 4% of SSRs. The estimated frequency of Class I SSRs (perfect repeats ≥20 nucleotides) was one SSR per 124.5 kb, whereas the frequency of Class II (perfect repeats >10 nucleotides and ≫20 nucleotides) was one SSR per 25.6 kb. The dynamics of SSRs will be a powerful tool for taxonomic, phylogenetic, genome mapping and population genetic studies as SSR based markers show high levels of allelic variation, codominant inheritance and ease of analysis.     

德国小蠊全基因组中微卫星分布规律

【目的】分析德国小蠊 Blattella germanica 全基因组中微卫星的数量和分布规律,并对外显子中含有微卫星的基因进行功能注释。【方法】使用微卫星搜索软件查找德国小蠊基因组中微卫星的数量、重复次数以及所有微卫星的位置信息,编写Python脚本对微卫星进行定位,并通过Blast2Go和KASS程序对外显子中含有微卫星的基因进行功能注释。【结果】共找到1~6碱基重复类型的微卫星序列604 386个,总长度15 301 255 bp,约占全基因组序列（约2.04 Gb）的0.75%,分布频率为1/3.37 kb,微卫星序列的长度主要在12~60个碱基长度范围内。不同类型的微卫星中,三碱基（226 876）重复类型微卫星数量最多,占微卫星总数的37.54%;四碱基（150 355）重复类型次之,占微卫星总数的24.88%;其余依次是单碱基（141 167）、二碱基（60 877）、五碱基（21 570）和六碱基（3 541）重复类型,分别占微卫星总数的23.36%, 10.07%, 3.57%和0.59%。出现最多的重复拷贝类别有：ATT, AAT, A, T, AAAT, ATTT和AT,共411 789个微卫星,占微卫星总数的68.13%,这7种类别的微卫星数量均大于30 000个。共有2 372个微卫星在外显子上,它们分别位于1 481个基因上。GO功能注释结果表明,其中434条归类于细胞组分(cellular component),402条归类于分子功能(molecular function),660条归类于生物学过程(biological process)。KEGG通路分析结果表明,与新陈代谢相关的基因最多（380个）,其次是与机体系统相关的（276个）,与遗传信息进程相关的基因最少（92个）。【结论】本研究为进一步系统深入分析德国小蠊微卫星功能及微卫星分子标记筛选打下了基础。     

Characterization of rabbit DNA micros extracted from the EMBL nucleotide sequence database

Microsatellite polymorphisms are invaluable for mapping vertebrate genomes. In order to estimate the occurrence of microsatellites in the rabbit genome and to assess their feasibility as markers in rabbit genetics, a survey on the presence of all types of mononucleotide, dinucleotide, trinucleotide and tetranucleotide repeats, with a length of about 20 bp or more, was conducted by searching the published rabbit DNA sequences in the EMBL nucleotide database (version 32). A total of 181 rabbit microsatellites could be extracted from the present database. The estimated frequency of microsatellites in the rabbit genome was one microsatellite for every 2–3 kb of DNA. Dinucleotide repeats constituted the prevailing class of microsatellites, followed by trinucleotide, mononucleotide and tetranucleotide repeats, respectively. The average length of the microsatellites, as found in the database, was 26, 23, 23 and 22 bp for mono-, di-, tri- and tetranucleotide repeats, respectively. The most common repeat motif was AG, followed by A, AC, AGG and CCG. This group comprised about 70% of all extracted rabbit microsatellites. About 61% of the microsatellites were found in non-coding regions of genes, whereas 15% resided in (protein) coding regions. A significant fraction of rabbit microsatellites (about 22%) was found within interspersed repetitive DNA sequences.     

Mining and gene ontology based annotation of SSR markers from expressed sequence tags of Humulus lupulus

Humulus lupulus is commonly known as hops, a member of the family moraceae. Currently many projects are underway leading to the accumulation of voluminous genomic and expressed sequence tag sequences in public databases. The genetically characterized domains in these databases are limited due to non-availability of reliable molecular markers. The large data of EST sequences are available in hops. The simple sequence repeat markers extracted from EST data are used as molecular markers for genetic characterization, in the present study. 25,495 EST sequences were examined and assembled to get full-length sequences. Maximum frequency distribution was shown by mononucleotide SSR motifs i.e. 60.44% in contig and 62.16% in singleton where as minimum frequency are observed for hexanucleotide SSR in contig (0.09%) and pentanucleotide SSR in singletons (0.12%). Maximum trinucleotide motifs code for Glutamic acid (GAA) while AT/TA were the most frequent repeat of dinucleotide SSRs. Flanking primer pairs were designed in-silico for the SSR containing sequences. Functional categorization of SSRs containing sequences was done through gene ontology terms like biological process, cellular component and molecular function.     

Eucalyptus microsatellites mined in silico: survey and evaluation

Eucalyptus is an important short rotation pulpy woody plant, grown widely in the tropics. Recently, many genomic programmes are underway leading to the accumulation of voluminous genomic and expressed sequence tag sequences in public databases. These sequences can be utilized for analysis of simple sequence repeats (SSRs) and single nucleotide polymorphism (SNPs) available in the transcribed genes. In this study, in silico analysis of 15,285 sequences representing partial and full-length mRNA from Eucalyptus species for their use in developing SSRs or microsatellites were carried out. A total of 875 EST-SSRs were identified from 772 SSR containing ESTs. Motif size of 6 for dinucleotide and 5 for trinucleotide, tetranucleotide, and pentanucleotides were considered in locating the microsatellites. The average frequency of identified SSRs was 12.9%. The dinucleotide repeats were the most abundant among the dinucleotide, trinucleotide and tetranucleotide motifs and accounted for 50.9% of the Eucalyptus genome. Primer designing analysis showed that 571 sequences with SSRs had sufficient flanking regions for polymerase chain reaction (PCR) primer synthesis. Evaluation of the usefulness of the SSRs showed that EST-derived SSRs can generate polymorphic markers as all the primers showed allelic diversity among the 16 provenances of E. tereticornis.     

Comparison of simple sequence repeats in 19 Archaea

All organisms that have been studied until now have been found to have differential distribution of simple sequence repeats (SSRs), with more SSRs in intergenic than in coding sequences. SSR distribution was investigated in Archaea genomes where complete chromosome sequences of 19 Archaea were analyzed with the program SPUTNIK to find di- to penta-nucleotide repeats. The number of repeats was determined for the complete chromosome sequences and for the coding and non-coding sequences. Different from what has been found for other groups of organisms, there is an abundance of SSRs in coding regions of the genome of some Archaea. Dinucleotide repeats were rare and CG repeats were found in only two Archaea. In general, trinucleotide repeats are the most abundant SSR motifs; however, pentanucleotide repeats are abundant in some Archaea. Some of the tetranucleotide and pentanucleotide repeat motifs are organism specific. In general, repeats are short and CG-rich repeats are present in Archaea having a CG-rich genome. Among the 19 Archaea, SSR density was not correlated with genome size or with optimum growth temperature. Pentanucleotide density had an inverse correlation with the CG content of the genome.