24 resultados para QUANTITATIVE GENETIC-ANALYSIS

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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Recombinant "all-fish" growth hormone gene (GH) was microinjected Into the fertilized eggs of carp. A comparison between the growth traits of transgenics and non-transgenics was carried out, and the transgenic individuals with significant "fast-growing" effect were successfully gained. A comparison on the reproductivities was also given out between the transgenics and their non-transgenic siblings, and showed that the reproductive capacity of transgenics was substantially equivalent to those of the non-transgenics. On the other hand, the genetic separation and the characteristic distribution of the F-1 generation were genetically analyzed, which gave solid evidence for the hypothesis that 2-3 chromosomes are integrated with transgene. In addition, the distinct biological effects for multisite-integrated transgenes were further discussed. The present study opens a door for the breeding of "fast-growing" transgenic fish.

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Inter-simple sequence repeat (ISSR) analysis was used to assess eleven pairs of Undaria pinnatifida (Harv.) Suringar male and female gametophytes. After screening fifty primers, 18 ISSR primers were selected for final analysis. A total of 104 loci were obtained, of which 77 were polymorphic, among the gametophytes studied. Genetic relationships were analyzed with simple matching (S), Jaccard's (J) and Dice's (D) distance coefficients. Little genetic variations were found among the selected Undaria gametophytes, for instance, the genetic distances ranging from 0.010 to 0.125 with Dice coefficients. UPGMA dendrograms showed that 11 pairs of Undaria gametophytes were distributed into five groups. Most Undaria strains cultivated in China exhibited closely genetic relationships with the strains from Japan. However, gametophytes from Qingdao appeared as distinct clades from other Undaria strains with all three distance coefficients used. Mantel test showed that the three distance measurements generated congruent clustering patterns on the same data. Our results demonstrated the feasibility of applying ISSR markers for genetic analysis of Undaria gametophytes. (c) 2006 Elsevier B.V. All rights reserved.

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Eleven pairs of Undaria pinnatifida (Harv.) Suringar gametophytes were identified with random amplified polymorphic DNA (RAPD) technique. After screening 100 primers, 20 ten-base primers were determined for the RAPD analysis. A total of 312 polymorphic loci were obtained, of which 97.7% were polymorphic. The primer S198 was found to distinguish all the selected Undaria pinnatifida gametophytes. The genetic distances between each two of the twenty-two U. pinnatifida gametophytes ranged from 0.080 to 0.428, while the distances to the Laminaria was 0.497 on average. After reexamination, two sequences characterized amplification region (SCAR) markers were successfully converted, which could be applied to U. pinnatifida germplasm identification. All these results demonstrated the feasibility of applying RAPD markers to germplasm characterization and identification of U. pinnatifida gametophytes, and to provide a molecular basis for Undaria breeding.

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Twenty microsatellite markers (Po1, Po13, Po33, Po35, Po42, Po48, Po56, Po89, Po91, kop6, kop7, kop8, kop12, kop15, kop18, kop21, kop22, kop23, kop26, Po-strl) were used to assess the meiogynogenetic and mitogynogenetic stocks of the left-eyed flounder, Paralichthys olivaceus, which were derived from single pair crossing. Twelve of the 20 loci utilized showed heterozygosity in the female and were mapped in relation to their centromeres in the meiogynogenetic diploid flounder. Microsatellite-centromere map distance, calculated under the assumption of complete interference, ranged from 15.8 cM for kop22 to 50 cM for Po13, Po56 and Po89. Excluding the kop22, the heterozygosities of the rest of the loci were close to 100%, suggesting the occurrence of near complete interference on the chromosome arms that carried these loci. In the mitogynogenetic diploid flounder, each individual showed exact homozygousity and the segregation profiles did not deviate from the Mendelian 1: 1 pattern. The results indicated that there was no lethal gene linked with the loci analyzed. Such high interference accounted for the high recombination rates and large map distances. The Po13 and Po56 loci, Po91 and kop18 loci, kop15 and kop21 loci are tightly linked on the same chromosome arm in pairs.

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Inter-simple sequence repeat (ISSR) analysis was used to assess genetic diversity among 10 pairs of male and female Laminaria gametophytes. A total of 58 amplification loci was obtained from 10 selected ISSR primers, of which 34 revealed polymorphism among the gametophytes. Genetic distances were calculated with the Dice coefficient ranging from 0.006 to 0.223. A dendrogram based on the unweighted pair-group method arithmetic (UPGMA) average showed that most male and female gametophytes of the same species were clustered together and that 10 pairs of gametophytes were divided into four groups. This was generally consistent with the taxonomic categories. The main group consisted of six pairs of gametophytes, which were selected from Laminaria japonica Aresch. by intensive inbreeding through artificial hybridization. One specific marker was cloned, but was not converted successfully into a sequence characterized amplified region (SCAR) marker. Our results demonstrate the feasibility of applying ISSR markers to evaluate Laminaria germplasm diversities.

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Sex evolution has been a debating focus in evolutionary genetics. In lower vertebrates of reptiles, amphibians, and fish, a species or a bioform reproduces either sexually or asexually but never both. A few species were found to consist of all females in fish. These all-female species can propagate by asexual reproduction modes, such as gynogenesis and hybridogenesis. However, the coexistence of sexuality and asexuality in a single species was recently noted only in a cyprinid fish silver crucian carp, Carassius auratus gibelio. This fish had been demonstrated to be capable of gynogenesis stimulated by sperm from other related species. Surprisingly, natural populations of this fish consist of a minor but significant portion (approx. 20%) of males. As different clones with specific phenotypic and genetic characteristics have been found, and RAPD markers specific to each clone have recently been identified, this fish offers many advantages for analyzing whether or not genetic recombination occurs between different clones. In this study, artificial propagation was performed in clone F and clone D. Ovulated eggs from clone F were divided into two parts and respectively inseminated with sperm from a clone D male and from a red common carp (Cyprinus carpio) male. The control clone D individuals were selected from gynogenetic offspring of clone D activated by sperm of red common carp. The phenotype and sex ratio in the experimental groups were also observed. Using RAPD molecular markers, which allow for reliable discrimination and genetic analysis of different clones, we have revealed direct molecular evidence for gonochoristic reproduction in the gynogenetic silver crucian carp and confirmed a previous hypothesis that the silver crucian carp might reproduce both gynogenetically and gonochoristically. Therefore, we conclude that the silver crucian carp possesses two reproductive modes, i.e., gynogenetic and gonochoristic reproduction. The response mechanism of two reproductive development modes may be the first discovery in vertebrates. Additionally, we discuss the evolutionary implication between gynogenetic and gonochoristic reproduction modes and the contribution of the minor proportion of males to genetic flexibility in the gynogenetic silver crucian carp.

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高等植物种子胚乳贮藏蛋白是种子发芽时的主要氮源,也是人类和动物食用植物蛋白的主要来源。大麦种子胚乳贮藏蛋白主要是醇溶蛋白(hordeins),占大麦胚乳总蛋白的50–60%。根据大麦醇溶蛋白的大小和组成特点,大麦醇溶蛋白被划分为三种类型:富硫蛋白亚类(B,γ-hordeins)、贫硫蛋白亚类(C-hordeins)以及高分子量蛋白亚类(D-hordeins)。B组和C组醇溶蛋白是大麦胚乳的两类主要贮藏蛋白,它们分别占大麦总醇溶蛋白成分的70–80%和10–12%。遗传分析表明,大麦B、C、D和γ-组醇溶蛋白分别是由位于大麦第五染色体1H(5)上的Hor2、Hor1、Hor3和Hor5位点编码。Hor2位点编码大量分子量相同但组成不同的B组醇溶蛋白(B-hordein)。B-hordein的种类、数量和分布是影响大麦酿造、食用及饲养品质的重要因素之一。为深入了解B-hordein基因家族的结构和染色体组织,探明Hor2位点基因表达的发育调控机制,最终达到改良禾谷类作物籽粒品质的目的,本研究以青藏高原青稞为材料,采用同源克隆法,分别克隆B-hordein基因和启动子,通过原核生物表达验证B-hordein基因功能,并利用实时定量PCR探索B-hordein基因表达时空关系,取得如下研究结果: 1. 以具有特殊B组醇溶蛋白亚基组成的9份青藏高原青稞为材料,根据GenBank中三个B-hordein基因序列(GenBank No. X03103, X53690和X53691)设计一对引物,通过PCR扩增,获得23个B-hordein基因克隆并对其进行了序列分析。核苷酸序列分析表明,所有克隆均包含完整的开放阅读框。有11个克隆都存在一个框内终止密码子,推测这11个克隆可能是假基因。推测的氨基酸序列分析表明,所有大麦B-hordein具有相似的蛋白质基本结构,均包括一个高度保守的信号肽、中间重复区以及C-端结构域。不同大麦种重复区内重复基元的数目有较大差异。青稞材料Z07–2和Z26的B-hordeins仅具有12个重复基元结构,更接近于野生大麦。这些重复基元数目的差异导致了重复区序列长度和结构的变异。这种现象极可能是由于醇溶谷蛋白基因在进化过程中染色体的不平衡交换或复制滑动所造成的。对所克隆基因和禾本科代表性醇溶谷蛋白基因进行聚类分析,结果表明所有来自栽培大麦的B-hordeins聚类成一个亚家族,来自野生大麦的B-hordeins以及普通小麦的LMW-GS聚类成另外一个亚家族,表明这两个亚家族的成员存在显著差异。此外,我们发现B-hordein基因推测的C-末端序列具有一些有规律的特征:即具有相同C-末端序列的B-hordein基因在系统发生树中聚类为同一个亚组(除BXQ053,BZ09-1,BZ26-5分别单独聚为一类外)。这个特征将有助于我们对所有B组醇溶蛋白基因家族成员进行分类,避免了在SDS-PAGE电泳图谱上仅依靠大小分类的局限性。 2. 根据上述克隆的青稞B-hordein基因的5’端序列设计三条基因特异的反向引物,以青稞Z09和Z26的基因组DNA为模板,采用SON-PCR和TAIL-PCR技术分离克隆出8个B-hordein基因的上游调控序列(命名为Z09P和Z26P)。序列分析表明,推测的TATA box位于–80 bp,CAAT–like box位于–140 bp处。此外,Z09P和Z26P中有六个序列在–300 bp处均存在一个由高度保守的EM基序和类GCN4基序构成的胚乳盒(Endosperm Box,EB),在约–560 bp处存在一个胚乳盒类似结构。而Z09P-2和Z26P-3不存在保守的胚乳盒或其类似结构,预示着这两个启动子所调控的基因表达可能受不同类型反式作用因子的调节,推测该启动子对基因的表达调控具有多样性。 3. 将B-hordein基因的开放阅读框定向克隆到表达载体pET-30a中,将其导入大肠杆菌表达菌株BL21中进行外源基因的诱导表达以验证所克隆基因的功能。结果表明仅含重组子pET-BZ07-2和pET-BZ26-5的BL21细菌有目的表达蛋白产生。在诱导3 h时的蛋白表达量最高;3 mM IPTG诱导的蛋白表达量要高于1 mM IPTG诱导的表达量。这为分离纯化B-hordein蛋白以及进一步研究其对大麦籽粒品质的影响奠定基础。 4. 根据从青稞Z09和Z26中分离克隆的B-hordein基因序列设计一对基因特异的引物,同时,选择大麦α-微管蛋白基因(GenBank no. U40042)为看家基因并设计特异引物,利用实时荧光定量PCR检测了青稞籽粒4个胚乳发育时间段的B-hordein基因表达,荧光定量结果显示:两份材料中B-hordein基因的表达量均随发育过程的进行而逐渐升高。Z09中B-hordein基因在开花后7天开始转录,而Z26开花4天后就有低水平B-hordein的表达,这表明Z26中B-hordein基因可能比Z09表达的较早或者Z09中B-hordein基因表达水平较低以致于不能被检测到。此外,在4个不同的胚乳发育时期中,Z26中B-hordein基因的表达量均高于Z09材料。在开花12天到18天的过程中,Z09和Z26中B-hordein基因的表达水平有一个急剧性的升高。这说明在不同胚乳发育时期,Hor2位点的B-hordein等位基因变异体存在mRNA的差异表达。 Seed endosperm storage proteins in higher plants are the main resources of nitrogen for germinating and plant proteins for human and animals. Barley prolamins (also called hordeins) are the major storage proteins in the endosperm and account for 50–60% of total proteins. Hordeins are classically divided into three groups: sulphur-rich (B, γ-hordeins), sulphur-poor (C-hordeins) and high molecular weight (HMW, D-hordeins) hordeins based on the size and composition. B-hordeins and C-hordeins are two major groups and each respectively account for about 70-80% and 10-12% of the total hordein fraction in barley endosperm. Genetic analysis showed that B-, C-, C-, γ-hordeins are encoded by Hor2, Hor1, Hor3 and Hor5 locus on the chromosome 1H (5). Hor2 locus is rich in alleles that encode numerous heterogeneous B-hordein polypeptides. It is reported that B-hordein species, quantity and distribution are significant factors affecting malting, food and feed quality of barley. To understand comprehensively the structure and organization of B-hordein gene family in hull-less barley and explore the developmental control mechanisms of Hor2 locus gene expression and eventually to better exploitation in crop grain quality improvement, we isolated and cloned B-hordein genes and promotors of hull-less barley from Qinghai-Tibet Plateau by PCR, and testified their expression founction in bacteria expression system and explore their spatial and temporal expression pattern by quantitative real time PCR. Our results are as followed, 1. Twenty-three copies of B-hordein gene were cloned from nine hull-less barley cultivars of Qinghai-Tibet Plateau with special B-hordein subunits and molecularly characterized by PCR, based on three B-hordein genes published previously (GenBank No. X03103, X53690 and X53691). DNA sequences analyses confirmed that the six clones all contained a full-length coding region of the barley B-hordein genes. Eleven clones all contain an in-frame stop codon and they are probably pseudogenes. The analysis of deduced amino acid sequences of the genes shows that they have similar structures including signal peptide domain, central repetitive domain, and C-terminal domain. The number of the repeats was largerly variable and resulted in polypeptides in different sizes or structures among the genes. Twelve such repeated motifs were found in Z07–2 and Z26, and they are close to those of the wild barleys, and it is most probably caused by unequal crossing-over and/or slippage during replication as suggested for the evolution of other prolamins. The relatedness of prolamin genes of barley and wheat was assessed in the phylogenetic tree based on their polypeptides comparison. Our phylogenetic analysis suggested that the predicted B-hordeins of cultivated barley formed a subfamily, while the B-hordeins of wild barleys and the two most similar sequences of LMW-GS of T. aestivum formed another subfamily. This result indicated that the members of the two subfamilys have a distinctive difference. In addition, we found the B-hordeins with identical C-terminal end sequences were clustered into a same subgroup (except BXQ053,BZ09-1 and BZ26-5 as a sole group, respectively), so we believe that B-hordein gene subfamilies possibly can be classified on the basis of the conserved C-terminal end sequences of predicted polypeptide and without the limit of SDS-PAGE protein banding patterns. 2. The specific primers were designed according to the published sequences of barley B-hordein genes from Z09 and Z26. Using total DNA isolated from them as the templates, eight clones (designated Z09Pand Z26P) of upstream sequences of the known B-hordein genes was obtained by TAIL-PCR and SON-PCR. Sequences analysis shows that the putative TATA box was present at position –80 bp and CAAT-like box at position –140 bp. Besides, a putative Endosperm Box including an Endosperm Motif (EM) and a GCN4-Like Motif was found at position –300 bp in six clones, and another Endosperm-like box was found at positon –560 bp. While the Endosperm Box or Endosperm-like box was not found in Z09P-2 and Z26P-3. This may indicate that gene expression drived by the two promtors was probably controlled by different trans-acting factors and the genetic control mechanism of corresponding gene expression may be diverse. 3. The B-hordein genic region coding for the mature peptide was cloned into expression vector pET-30a and transformed into bacterial strain BL21 for identifying gene expression fountion. Protein SDS–PAGE analysis showed that only the transformed lysate with the pET-BZ07-2 and pET-BZ26-5 constructs produced proteins related to B-group hordeins of barley, and the mounts of proteins induced by 3 mM IPTG and 3 h were higher than other conditions. This established a base for isolating and putifying B-hordein and further exploring their effects on barley grain quality. 4. The gene-specific primers of B-hordein genes from Z09 and Z26 were used for the quantification of B-hordein gene expression. The α-tubulin gene from Hordeum vulgare subsp. vulgare (GenBank accession number U40042) was used as a control gene. The result shows the transcription of the B-hordein genes in Z09 was found 7 days after flowering, while the transcription of the B-hordein genes in Z26 was found 4 days after flowering, but at a very low level, and it suggested that the B-hordein genes in Z26 probably expressed earlier than those in Z09, or the B-hordein genes in Z09 expressed at so a lower level than Z26 that it can not detected. In addition, B-hordein genes in Z26 accession showed higher expression levels than those in Z09 in four developing stages. Furthermore, a progressive increase in the expression levels of the B-hordein genes between 12 and 18 days after anthesis was observed in both Z09 and Z26. It implies that the B-hordein allelic variants encoded by Hor2 locus exist the differential expression in mRNA levels of during barley endosperm development.

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In Laminaria japonica Aresch breeding practice, two quantitative traits, frond length (FL) and frond width (FW), are the most important phenotypic selection index. In order to increase the breeding efficiency by integrating phenotypic selection and marker-assisted selection, the first set of QTL controlling the two traits were determined in F-2 family using amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers. Two prominent L. japonicas inbred lines, one with "broad and thin blade" characteristics and another with "long and narrow blade" characteristics, were applied in the hybridization to yield the F-2 mapping population with 92 individuals. A total of 287 AFLP markers and 11 SSR markers were used to construct a L. japonica genetic map. The yielded map was consisted of 28 linkage groups (LG) named LG1 to LG28, spanning 1,811.1 cM with an average interval of 6.7 cM and covering the 82.8% of the estimated genome 2,186.7 cM. While three genome-wide significant QTL were detected on LG1 (two QTL) and LG4 for "FL," explaining in total 42.36% of the phenotypic variance, two QTL were identified on LG3 and LG5 for the trait "FW," accounting for the total of 36.39% of the phenotypic variance. The gene action of these QTL was additive and partially dominant. The yielded linkage map and the detected QTL can provide a tool for further genetic analysis of two traits and be potential for maker-assisted selection in L. japonica breeding.

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本文研究了毛乌素沙地6个不同生态环境的柠条群体和1个锡盟草原站的小叶锦鸡儿群体的同工酶和种子蛋白的遗传变异。利用Brown等(/975)同工酶遗传分析方法对同工酶和种子蛋白的多态性进行了遗传分析。运用Shannon信息指数和Nei指数分析测定了锦鸡儿群体的遗传结构。结果表明: (l) Brown同工酶遗传分析的方法适合于柠条同工酶的遗传分析。 (2用LAP酶对柠条群体进行了精细的遗传结构研究。结果表明毛乌素沙地柠条群体的异交性。GST=D.134,即大部分的变异存在于群体内部,小部分的变异存在于群体之间。柠条群体的繁育系统与水分胁迫有关。随着生境变旱,繁育系统有向近交变化的趋势。 (3) Brown同工酶遗传分析方法也可以运用于种子蛋白遗传分析,柠条种子蛋白各亚基的遗传是孟德尔方式。 (4)由种子蛋白变异所统计测定的柠条群体的遗传分化系数GST=0.l81(Nei指数)或0.179(Shannon指数,Kongkiatngam改进)。群体变异水平按表型多样性依次为人工毛条群体>锡盟群体>滩地群体>硬梁群体>软梁群体>丘下群体>丘上群体。按遗传多样性依次为人工毛条群体>软梁群体>锡盟群体>滩地群体和硬梁群体>丘上群体>丘下群体。群体间基因流水平Nm>/,遗传距离D<0.1。 还试验对玉兰、合欢、紫藤、绿豆几种植物种子蛋白变异的遗传分析。最后对同工酶,种子蛋白遗传分析和群体遗传结构进行了讨论并提出今后工作的一些建议。

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当前分子生物学的方法以惊人的速度渗透到生命科学研究的各个领域。植物对不断变化的环境逐步适应的过程中,积累了丰富的遗传多样性。与此同时,人类活动空间的不断扩大已经严重威胁到其他生命的生存和繁衍,越来越多的物种以越来越快的速度在我们还没有来得及认识它们时就已经永远地消失了。加快物种鉴定和保护的步伐就必须发展更多能充分揭示物种遗传多样性的实验技术,从具有丰富遗传多样性的野生资源中寻找到更多能够服务于人类可持续发展的基因资源。本文以杨树杂交后代过氧化物同工酶和RAPD分析为基础,论证了我们改进的RAPD方法用于遗传分析的可行性。在前期工作的基础上,进一步测定了野大豆自然群体的耐盐性变异,并且用微卫星和RAPD分析的方法研究分子标记与DXA变异、植株耐盐性之间的关系。对四个可能与抗盐性有关的RAPD片段进行克隆、测序,并进行序列比较。由此得出以下结论: 1、在本文的实验条件下,杨树同工酶和RAPD分析均表明,RAPD标记在亲本及其杂交后代中性状比例符合孟德尔遗传规律,尽管有时也会出现遗传负载等机制引起的基因分布扭曲现象。 2、初步研究了个体发育阶段和环境条件对植株耐盐性的影响。结果表明,植物耐盐性不仅仅与外界的盐度有关,而且受发育阶段和其它环境条件(如,温度)的影响。但也发现了某些个体在各种条件下都具有较高的耐盐性,而且,不易受到其它环境条件的影响。 3、微卫星标记的结果表明,10对引物中的8对引物共检测到时17个等位基因,平均每对引物2.125个等位基因。本文的实验条件下,双核苷酸和三核苷酸的引物对扩增产物都没有出现“ghosts"条带或“打滑”现象。 4、有4个RAPD标记可能与野大豆群体的耐盐性有关,分别是OPCO8460bp、OPCO8213bp、OPCO2690bp、以及OPCO5270bp。测序结果与GenBank中的序列作同源性比较,结果显示,OPCO2_(690bp)与小麦、松树等植物的吉普赛性的逆转录转座子的部分区域(24--53)有很高的同源性(86-89%)。此外,OPCO2690bp与栽培大豆胞质谷氨酰胺合成酶(gs15)基因的启动子有高达95%的同源性。 5、本文实验条件下,RAPD扩增产物在限制性内切酶消化后,消化产物的多态性未见增大,也没有发现与耐盐性相关的多态位点。 6、野大豆自然群体DNA变异的研究中也可以应用SWAPP方法。

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Comparative genetic analysis between human and chimpanzee may detect genetic divergences responsible for human-specific characteristics. Previous studies have identified a series of genes that potentially underwent Darwinian positive selection during huma

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Giant panda hair samples obtained by noninvasive methods served as a source of DNA for amplification of seven giant panda microsatellite loci utilizing the polymerase chain reaction. Thirteen giant pandas held in Chinese zoos were tested for identification of paternity. Some males listed as sires have been excluded as the biological father of captive-born giant pandas. Because of the death of some potential sires, paternity is still not assigned for some giant pandas, although there is a high likelihood that paternity assignment could be made if postmortem samples are available for genetic analysis. The DNA microsatellite variation assayed by the test we have developed provides a rapid, highly informative, and noninvasive method for paternity identification in giant pandas. (C) 1994 Wiley-Liss, Inc.

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In this study, an IL-8 homologue has been cloned and identified from a reptile, Chinese soft-shelled turtle for the first time. The full-length cDNA of turtle IL-8 was 1188 bp and contained a 312 bp open reading frame (ORF) coding for a protein of 104 amino acids. The chemokine CXC domain, which contained Glu-Leu-Arg (ELR) motif and four cysteine residues, was well conserved in turtle IL-8. The 4924 bp genomic DNA of turtle IL-8 contained four exons and three introns. Phylogenetic analysis showed that the amino acid sequence of turtle IL-8 clustered together with birds. RT-PCR analysis showed that turtle IL-8 mRNA was constitutively expressed liver, spleen, kidney, heart, blood and intestine tissues of control turtles. Real-time quantitative PCR analysis further indicated that the turtle IL-8 mRNA expression was apparent in various tissues at 8 h and up-regulated significantly during 8 h-7 d after Aeromonas hydrophila infection. The present studies will help us to understand the evolution of IL-8 molecule and the inflammatory response mechanism in reptiles. (C) 2009 Elsevier Ltd. All rights reserved.

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Full-length and partial genome sequences of four members of the genus Aquareovirus, family Reoviridae (Golden shiner reovirus, Grass carp reovirus, Striped bass reovirus and golden ide reovirus) were characterized. Based on sequence comparison, the unclassified Grass carp reovirus was shown to be a member of the species Aquareovirus C The status of golden ide reovirus, another unclassified aquareovirus, was also examined. Sequence analysis showed that it did not belong to the species Aquareovirus A or C, but assessment of its relationship to the species Aquareovirus B, D, E and F was hampered by the absence of genetic data from these species. In agreement with previous reports of ultrastructural resemblance between aquareoviruses and orthoreoviruses, genetic analysis revealed homology in the genes of the two groups. This homology concerned eight of the 11 segments of the aquareovirus genome (amino acid identity 17-42%), and similar genetic organization was observed in two other segments. The conserved terminal sequences in the genomes of members of the two groups were also similar. These data are undoubtedly an indication of the common evolutionary origin of these viruses. This clear genetic relatedness between members of distinct genera is unique within the family Reoviridae. Such a genetic relationship is usually observed between members of a single genus. However, the current taxonomic classification of aquareoviruses and orthoreoviruses in two different genera is supported by a number of characteristics, including their distinct G+C contents, unequal numbers of genome segments, absence of an antigenic relationship, different cytopathic effects and specific econiches.

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To study nuclear transfer in the leach (Paramisgurnus dabryanus Sauvage), blastula and gastrula cells were fused with UV-inactivated oocytes by cell-to-cell electrofusion. To facilitate nuclear transfer, blastula and gastrula cells were cultured or incubated at 4 degreesC in different solutions. TC-199 medium supplemented with 20% calf serum was the best culture solution, and effectively retained the totipotence of blastula or gastrula cells for up to 10 days, It was found that gastrula cells incubated at 4 degreesC had the same totipotence as blastula cells, The optimal UV dosage for inactivation of the oocyte chromatin was 180-240 mJ cm(-2). Electrofusion was carried out in a cone-shaped fusion chamber, which permitted the recipient oocyte and the donor blastula cell to contact one another. The electrofusion procedure resulted in a 10% success rate of normal-appearing fish. Genetic analysis indicated that the nuclear material originated from the donor cell (blastomere) and the oocyte pronucleus did not take part in development.