基于28S rDNA序列的鞘藻目系统发育研究

作者进行了较广泛的样品采集,通过实验分离纯化培养得到多个鞘藻目种类的株系,并采用PCR技术新获得鞘藻目2属8个种类的部分28S rDNA序列,连同GenBank中的另两条序列,分析的物种涵盖了鞘藻目中的每个属。通过比较分析绿藻纲中包括此10条序列的共36个种类的同一基因序列,并选取Trebouxiophyceae中的椭圆小球藻(Chlorella ellipsoidea)和Fusochloris perforata作外类群,运用多种方法构建分子系统树,包括邻接法(Neighbor-Joining)、最大简

Phylogeny of freshwater parasitic copepods in the Ergasilidae (Copepoda : Poecilostomatoida) based on 18S and 28S rDNA sequences

The phylogenetic relationships among the Ergasilidae genera are poorly understood. In this study, 14 species from four genera in the Ergasilidae including Sinergasilus, Ergasilus, Pseudergasilus, and Paraergasilus were collected in China, and their phylogenetic relationships were examined using neighbor-joining, maximum parsimony, maximum likelihood, and Bayesian inference methods based on partial sequences of 18S and 28S ribosomal deoxyribonucleic acid, respectively. All the analyses suggest that the Sinergasilus and Paraergasilus are both monophyletic, but the Ergasilus is polyphyletic rather than monophyletic. Considering the relationships among the four genera, the phylogenetic analyses and subsequent hypothesis tests all suggest that Pseudergasilus clustered with some Ergasilus species may have a closer relationship with Sinergasilus rather than with Paraergasilus. It is proposed that the Sinergasilus and the Pseudergasilus species might have evolved from Ergasilus species.

Is the genus Digramma synonymous to the genus Ligula (Cestoda : Pseudophyllidea)? Evidence from ITS and 5 ' end 28S rDNA sequences

The genus Digramma (Cestoda: Pseudophyllidea) described by Cholodkovsky in 1915 differs from the genus Ligula only by the number of the reproductive organs per proglottis. However, the occurrence of transitional forms in Digramma raises much confusion concerning its generic validity. In the present study, cestodes previously designated as Digramma and Ligula were collected from lakes in the lower and middle reaches of the Yangtze River, and also from Qinghai Lake on Qingzang plateau, China. The entire internal transcribed spacer of the ribosomal DNA (ITS rDNA) and 5' end of 28S rDNA were compared between the Digramma and Ligula specimens. The low level of nucleotide variation between the two genera may imply that cestodes in the genus Digramma are paraphyletic to the Ligula genus, and Digramma is a synonym of Ligula. However, whether previously identified Digramma cestodes represent different species in the genus Ligula requires further investigation.

Phylogenetic relationships among two species of golden monkey and three species of leaf monkey inferred from rDNA variation

Restriction maps of rDNA repeats of five species of Colobinae and three outgroup taxa, Hylobates leucogenys, Macaca mulatta, and Macaca irus, were constructed using 15 restriction endonucleases and cloned 18S and 28S rRNA gene probes. The site variation between Rhinopithecus roxellana and Rhinopithecus bieti is comparable to that between Presbytis francoisi and Presbytis phayrei, implying that R. bieti is a valid species rather than a subspecies of R. roxellana. Phylogenetic analysis on the 47 informative sites supports the case for Rhinopithecus being an independent genus and closely related to Presbytis. Furthermore, branch lengths of the tree seem to support the hypothesis that the leaf monkeys share some ancestral traits as well as some automorphic characters.

Molecular Phylogeny of Geographical Isolates of Bursaphelenchus xylophilus: Implications on the Origin and Spread of this Species in China and Worldwide

The genetic diversity and phylogeny of 26 isolates of Bursaphelenchus xlophilus from China, Japan, Portugal and North America were investigated based on the D2/3 domain of 28S rDNA, nuclear ribosomal Internal Transcribed Spacer (ITS) sequences, and random amplified polymorphic DNA (RAPD) analysis. The genetic diversity analysis showed that the D2/3 domain of 28S rDNA of isolates of B. xlophilus from China, Portugal, Japan and the US were identical and differed at one to three nucleotides compared to those from Canada. ITS sequences of isolates from China and Portugal were the same; they differed at one or two nucleotides compared to those of Japanese isolates and at four and 23 nucleotides compared to those front the US and Canada, respectively. The phylogenetic analysis indicated that Chinese isolates share a common ancestor with one of the two Japanese clades and that the Canadian isolates form a sister group of the clade comprised of isolates from China, Portugal,Japan, and the US. The relationship between Japanese isolates and those from China was closer than with the American isolates. The Canadian isolates were the basal group of B. xylophilus. This suggests that B. xlophilus originated in North America and that the B. xylphilus that occurs in China could have been first introduced from Japan. Further analysis based on RAPD analysis revealed that the relationship among isolates from Guangdong, Zhejiang, Shandong, Anhui provinces and Nanjing was the closest, which suggests that pine wilt disease in these Chinese locales was probably dispersed from Nanjing, where this disease first occurred in China.

A DNA-sequence based phylogeny for triculine snails (Gastropoda : Pomatiopsidae : Triculinae), intermediate hosts for Schistosoma (Trematoda : Digenea): phylogeography and the origin of Neotricula

Partial (DNA) sequences were examined for one nuclear (28S rRNA gene) and one mitochondrial (16S rRNA) locus for nine species of pomatiopsid snail (Gastropoda: Rissooidea: Pomatiopsidae) from south-east Asia and south-west China. Fresh field samples were

耐酸产甲烷菌的分离及其复合菌剂的研究

本文从成都龙泉垃圾填埋场和宜宾造纸厂分离到耐酸性能优良的高温产甲烷菌RY3和中温产甲烷菌SH4，并将其与实验室现有的利用不同底物的产甲烷菌配伍组合成了复合菌剂。采用活性污泥作为固体附着物，研制出了固体产甲烷菌复合菌剂。 菌株RY3的pH耐受范围为5.5～10.5，最适生长pH 6.0～8.0。菌株RY3为革兰氏阳性，长杆状，多数单生，不运动；菌落浅黄色，形状近圆形；利用H2+CO2或甲酸盐作为唯一碳源生长，不利用乙酸盐，对氯霉素非常敏感。该菌最适生长温度为55℃～65℃，最适NaCl浓度为0～2%。根据形态和生理生化特性及16S rDNA序列分析将其初步定为热自养甲烷热杆菌（Methanothermobacter thermautotrophicus）。添加RY3菌液与仅添加厌氧污泥作为接种物相比一周内可使达到最大产甲烷速率所需时间缩短三分之二，甲烷总产量提高约1.8倍。菌株SH4的生长pH范围5.5～9.5，其对酸碱具有良好的适应性，培养3天后，在初始pH值为6.0～8.0的培养基中甲烷产量相差不大，且基本达到最大产量。SH4革兰氏染色阳性，短杆状，多数单生，不运动；菌落近圆形，微黄；利用H2+CO2或甲酸盐作为唯一碳源生长，不利用乙酸盐，对氯霉素非常敏感。SH4最适生长pH 为7.0，最适生长温度为35℃，最适NaCl浓度为0～1.5%。实验表明，添加SH4菌液与仅添加厌氧污泥作为接种物相比可使产甲烷启动时间缩短三分之一，甲烷总产量亦有大幅提高。从形态和生理生化特征以及16S rDNA序列分析表明SH4为嗜树木甲烷短杆菌（Methanobrevibacter arboriphilus）。 以活性污泥为附着物，与培养基和菌种经搅拌后厌氧发酵可得产甲烷菌固体复合菌剂。固体复合菌剂的pH耐受范围为5.5～9.5，温度耐受范围为15℃～65℃，表明其对环境的适应性较强。以猪粪为底物进行厌氧发酵，接种复合菌剂进行试验，以接种实验室长期富集的产甲烷厌氧污泥作为对照，在20℃时，发酵甲烷浓度与对照基本一致，但每日产气量优于对照，第15天时接种复合菌剂的发酵瓶每日产气量是对照的1.59倍；50℃时达到最大甲烷含量所需时间比对照缩短三分之二，三周内总产气量约为对照的2.7倍，甲烷总产量约为2.8倍。以不加接种物为对照，接种复合菌剂20℃时发酵甲烷含量达到50%约需2周，对照2周内甲烷含量最高仅为4.3%；50℃时接种复合菌剂发酵仅需约1周甲烷含量便可达50%，对照则至少需要2周。 In this paper, high-temperature Methanogen RY3 and middle-temperature SH4 were isolated from Chengdu Longquan refuse landfill and Yibin paper mill. They could be used to make compound inoculum that producing methane with the existing Methanogens utilized different substrate. With using anaerobic activated sludge be solid fixture, the process had been designed to produce solid compound inoculum. Strain RY3 possessed excellent capacity of acid and alkali-tolerant. The pH-tolerant scale of RY3 was 5.5～10.5 and its optimum pH value for growth was 6.0～8.0. RY3 was G+, long-rod shape, monothetic and nonmotile, the colony was pale yellow with suborbicular-shape. Formate or H2+CO2 but not acetate was utilized by RY3 as sole C-source, and it was very sensitive to chloramphenicol. Besides, strain RY3 grew fastest at 55℃～65 and 0℃～2% NaCl. Characteristics of modality and physiology with sequence analysis of the 16s rDNA gene of strain RY3 preliminarily showed that it was Methanothermobacter thermautotrophicus. The experiments indicated that the time which began to produce methane with the highest velocity could be shortened two third by adding RY3 in one week, and the total methane production also was 1.8 times than before. Strain SH4 possessed wide scale of growing pH（5.5～9.5）and excellent ability of acclimatizing itself to acid-alkali. The methane production had no apparent difference among those cultivated in different initial pH（6.0～8.0）after three days and equaled to the maximum production basically. Cells of SH4 were G+, short-rod sharp, monothetic and nonmotile. The colony was pale yellow with suborbicular-shape. Formate or H2+CO2 but not acetate was utilized by SH4 as sole C-source, and it was very sensitive to chloramphenicol. Besides, it grew fastest at pH 7.0，55 ℃～65 and 0℃～2% NaCl concentration. The experiment indicated the time that began to produce methane could be shortening one third by adding SH4. And the total methane production also rose apparently. Characteristic of modality and physiology with sequence analysis of the 16S rDNA gene of strain SH4 demonstrated it was Methanobrevibacter arboriphilus. The activated sludge was utilized as fixture, mixed with culture medium and inocolum, that the solid compound inoculum could be produced by anaerobic fermentation. The compound inoculum could grow between pH 5.5～9.5, 15℃～65. It demonstrated the compound inoculum ha℃ve great ability of adapting to circumstance. In the experiment that making pig manure be substrate and taking the anaerobic sludge producing methane that cultured in long term in laboratory to be comparison, the concentration of methane in fermentation added compound inoculum almost equal to the comparison at 20℃, but the volume of gas production could be a little higher. The gas production everyday inoculated compound inoculum was 1.59 times to comparison. The time that the concentration of methane to maximum could be shortening by two third by adding compound inoculum, and the total gas production was 2.7 times to comprison while the total methane production was 2.8 times. If take the no inoculum be the comprasion, anaerobic fermentation added compound inoculum made the concentration of methane to 50% in 2 weeks but the comparison only to 4.3% at 20℃. The time that the concentration of methane to 50% by adding compound inoculum only need 1 week, but the comparison need 2 weeks at 50℃.

Purification and characterization of the chitosanase from Aeromonas sp HG08

In this work, the characterization of a chitosanase-producing bacterium isolated from soil was reported and this strain was grouped under the genus Aeromonas by virtue of its morphological, physiological properties and 16S rDNA gene sequences. It is the first report that the genus Aeromonas could produce chitosanase. Aeromonas sp. HG08 could secrete the chitosanase ( named AsChi) with molecular weight of 70 kDa. The optimum pH and temperature of AsChi was 6.0 and 55 degrees C, respectively. The activity of AsChi was markedly enhanced by Mn2+ and inhibited by Fe3+, Cu2+, Ag+ and Hg2+; additionally, the activity of AsChi was increased with the degree of deacetylation ( DDA) of chitosan. Through viscosimetric assay, AsChi probably hydrolyzed chitosan in an endo-type fashion.

牡蛎染色体的分子生物学分析

本研究应用显带技术和荧光原位杂交(Fluorescence in situ hybridization，FISH)技术，鉴定了牡蛎的染色体；应用FISH方法定位了一系列的重复序列和大分子的P1克隆DNA；制备了染色体特异性探针。应用FISH特异性探针成功地鉴定了长牡蛎的三体10。结果如下：1．分析了G带和C带在美洲牡蛎染色体上的分布。G带在每一条染色体上的带型不同，某些染色体间(如第1对和第4对染色体，第7对和第9对染色体)的带型差别不是很明显。G带型容易受染色体收缩程度的影响。C带型重复性较好，染色体带型较清楚，分布在染色体的端粒区域和着丝粒区域。G带和C带带型能够用来鉴定牡蛎的染色体，但是重复性低和带型差异不显著，并不适合常规的染色体鉴定。2．早期胚胎和担轮幼虫制备的染色体适合于FISH分析。染色体制备方法重复性好，可适用于其它贝类的染色体制备。3．研究了重复序列基因--rDNA的定位：1)18S-5.8S rDNA在研究的五种巨蛎属Crassostrea牡蛎均只有一个位 点。太平洋种(C.gigas，C. ariakensis和C. plicatula)中，杂交信号位于最短的染色体一第10对染色体长臂的端粒区域，在大西洋种(C. virginica和C. rhizophorae)中，同一序列定位在第2对染色体短臂的端粒区域。2)18S-28S rDNA在两种蛤中有两个位点。rDNA探针定位在侏儒蛤(Mulinis Lateralis)的第15对和第19对染色体的端粒区域，同一序列定位在硬壳蛤(Mercenaria mercenaria)的第10对染色体的长臂和第12对染色体短臂的端粒区域。信号强度在两对染色体之间有差异。 3)5s rDNA位于美洲牡蛎的第5对染色体的短臂上靠近着丝粒区域和第6 对染色体的短臂的中间区域。信号强度在两对染色体之间没有显著差异。5S rDNA探针可以作为鉴定和识别第5对和第6对染色体的特异性探针。4．研究了一些重复序列的定位1)两个短的重复序列1G8，1P2均产生很强的荧光信号分布在美洲牡蛎所有的染色体上。在低严谨条件下，这些序列均产生很强的信号散布在所有的染色体上。在高严谨条件下，信号强度大大减弱，但是信号仍散布在所有的染色体上。这些重复序列散布在美洲牡蛎的整个基因组中。2)高度重复序列Cgl70产生的信号分布在长牡蛎的7对染色体的着丝粒区域，没有发现间区信号。在第1对，第2对，第4对和第7对染色体上的荧光信号强且稳定。在第5对，第8对和第10对染色体上的信号相对弱且不稳定。在剩余的染色体上(第3对，第6对和第9对染色体)没有检测到荧光信号。结果表明此卫星序列是一个着丝粒卫星序列。在美洲牡蛎的染色体上没有检测到荧光信号，表明了这个着丝粒卫星序列在这两种牡蛎中的分布存在着显著的差异。3)脊椎动物端粒序列(TTAGGG)n的FISH信号局限在四种双壳贝类(美洲牡蛎，the mangrove oyster，硬壳蛤，侏儒蛤)所有染色体的端粒区域，没有发现间区信号的存在。研究结果与已报道的研究结果表明脊椎动物端粒序列或许存在于所有双壳贝类的染色体末端。双壳贝类是目前研究过的唯一含有脊椎动物端粒序列DNA的无脊椎动物。4)研究了RAPD探针在美洲牡蛎染色体上的定位。大多数RAPD探针产生了多个信号散布在间期细胞核和所有的染色体上。引物OPX-03，OPX-04，OPX—06，OPG-02，OPM—04，OPM-11，0PS-02制备的探针在适宜的条件下产生特异性荧光 信号，分布在牡蛎的特定的染色体上。PCR特异性带产生的探针OPX—06—310和0PG-02—300产生了特异性的荧光信号：OPX—06—310产生的信号位于第5对染色体的短臂的近端粒区域，0PG—02—300探针定位到第3对染色体的短臂上。这两个探针是鉴定美洲牡蛎单条染色体的特异性探针。5．研究了大分子Pl克隆DNA(插入片断为80～100 kb)在美洲牡蛎染色体上的定位。Pl克隆DNA通过切口平移方法标记digoxigenin—11-dUTP用作FISH的探针。Cot-1 DNA作为竞争剂有效地抑制了Pl克隆序列中的重复序列产生的信号。杂交信号用fluorescein标记的anti—digoxigenin抗体来检测，用两层抗体rabbit-anti-sheep抗体和FITC anti—rabbit抗体来扩增信号。9个P1探针成功地定位在特定的染色体上。46—1探针杂交到第1对染色体的长臂靠近着丝粒区域；47-10探针定位到第2对染色体的长臂近端粒区域；Cvpl和48-13两探针定位到第3对染色体上：Cvpl位于短臂的端粒区域，48-13探针位于长臂的近着丝粒区域；48—10探针杂交到第4对染色体的长臂上；48-1探针杂交到第5对染色体长臂的近着丝粒区域；49-11探针位于第7对染色体长臂上；探针49-10和44-11位于第8对染色体长臂上。同时我们成功地将2个P1探针杂交到同一染色体分裂相中，进一步确定了Pl探针在美洲牡蛎染色体 上的定位。6．应用18S-28S rDNA探针成功地鉴定出长牡蛎非整倍体中的三体10。经鉴定AF-35，AF-39和AF-3三体家系属于三体10家系。rDNA探针分布在三条染色体上，即多出的一条染色体为染色体10。相应地在间期细胞核上有三个信号出现。AF-34和AF-36家系不属于三体10家系。rDNA探针分布在两条染色体上，相应地在间期细胞核上有两个信号出现。FISH和染色体特异性探针为非整倍体的鉴定提供了一个快速准确可靠的方法和途径。

Population genetic structure of the parasitic nematode Camallanus cotti inferred from DNA sequences of ITS1 rDNA and the mitochondrial COI gene

The population genetic structure of fish parasitic nematode, Camallanus cotti, collected from the Yangtze River, Pearl River and Minjiang River in China was investigated. From these parasites, the similar to 730 bp of the first internal transcribed spacer of ribosomal DNA (ITS1 rDNA) and the 428 bp of mitochondrial cytochrome c oxidase subunit I (COI) gene were sequenced. For the ITS1 rDNA data set, highly significant Fst values and low rates of migration were detected between the Pearl River group and both the Yangtze River (Fst = 0.70, P < 0.00001; Nm = 0.21) and Minjiang River (Fst = 0.73, P < 0.00001; Nm = 0.18) groups, while low Fst value (Fst = 0.018, P > 0.05) and high rate of migration (Nm = 28.42) were found between the Minjiang and the Yangtze rivers. When different host/locality populations (subpopulations) within each river were considered, subpopulations between the Yangtze River and Minjiang River had low Fst values (<= 0.12) and high Nm values (>3.72), while Pearl River subpopulations were significantly different from the Yangtze River and Minjiang River subpopulations (Fst >= 0.59; Nm < 1). The COI gene data set revealed a similar genetic structure. Both phylogenetic analyses and a statistical parsimony network grouped the Pearl River haplotypes into one phylogroup, while the Yangtze River and Minjiang River haplotypes formed a second group. These results suggested that the Yangtze River and Minjiang River subpopulations constituted a single reproductive pool that was distinct from the Pearl River subpopulations. In addition, the present study did not find host-related genetic differentiation occurring in the same drainage. (C) 2009 Published by Elsevier B.V.

猕猴属6个种的rDNA变异及其系统进化关系

以人28S,18S DNA为探针,用15种限制性内切酶构建了猕猴属6个种(M.mulatta、M.facsicularis、M.arctoides、M.assamensis、M.thibetana、M.nemestrina)和滇金丝猴(Rhinopithecus bieti),白颊长臂猿(Hylobates leucogenys)核糖体DNA重复单位的限制性内切酶图谱。红面猴(M.arctoides)与熊猴(M.assamensis)拥有完全相同的限制性内切酶图谱。基于内切酶图谱得到了68个信息位点并计算了各种rDNA重复型间的遗传距离。用PHYLIP version 3.5c软件包中的NEIGHBOR和RESTML程序,以滇金丝猴和白颊长臂猿为外群,构建了NJ树和最大似然树。两棵树的拓扑结构不完全一致,但恒河猴( (M.mulatta)和食蟹猴(M.facsicularis)总是位于树的基部。熊猴-红面猴(M.assamensis-M.arctoides)虽然与藏猴(M.thibetana)共享的限制性位点数更多,在NJ树上两类动物也最为接近,但在最大似然树中熊猴-红面猴却与平顶猴(M.nemestrina)聚在一起。因此,rDNA变异的数据尚不能对猕猴类动物进行有效的分组。

Phylogeny of the cuttlerishes (Mollusca : Cephalopoda) based on mitochondrial COI and 16S rRNA gene sequence data

To clarify cuttlefish phylogeny, mitochondrial cytochrome c oxidase subunit 1 (COI) gene and partial 16S rRNA gene are sequenced for 13 cephalopod species. Phylogenetic trees are constructed, with the neighbor-joining method. Coleoids are divided into two main lineages, Decabrachia and Octobrachia. The monophyly of the order Sepioidea, which includes the families Sepiidae, Sepiolidae and Idiosepiidae, is not supported. From the two families of Sepioidea examined, the Sepiolidae are polyphyletic and are excluded from the order. On the basis of 16S rRNA and amino acid of COI gene sequences data, the two genera (Sepiella and Sepia) from the Sepiidae can be distinguished, but do not have a visible boundary using COI gene sequences. The reason is explained. This suggests that the 16S rDNA of cephalopods is a precious tool to analyze taxonomic relationships at the genus level, and COI gene is fitter at a higher taxonomic level (i.e., family).

贾第虫rDNA的研究

典型的真核生物有四种rRNA（18S、5.8S、28S和5SrRNA）。一般18S、5.8S和28S的基因分别由转录间隔区（ITS）隔开而位于同一个转录单位上构成一个rRNA基因拷贝，多个rRNA基因拷贝串联形成rDNA。rDNA聚集在一起构成核仁组织区（NOR），成为核仁发生的位置。5SrRNA基因除在少数真核生物（如：酵母）中是和18S、28S rRNA基因位于同一个转录单位上外，一般是处在核仁以外的区域。贾第虫一度被认为是现存最原始的真核生物。支持这一观点的一个重要证据之一就是它还不具核仁结构。那么它的rDNA与典型真核生物的相比会有怎样的特点呢？本文在基因组的水平上对贾第虫的rDNA进行了全面调查分析，并对5S rRNA及其相关蛋白进行重点研究，得到如下结果和结论： 1）贾第虫的18S rRNA（1448bp）基因和28S rRNA（2300bp）基因比其他一些真核生物的（一般为1800bp和3400bp）要小的多，甚至比一些原核生物的相应的rRNA基因还要小。不仅如此，其5.8S rRNA基因和28SrRNA基因之间的转录间隔区（ITS2）比典型真核生物的对应区域也要短得多（只有54bp），且GC含量较高。结构预测表明该间隔区不能形成在许多真核生物中所能形成的保守的二级结构。更特别的是，贾第虫基因组中的rRNA基因序列大部分都是不完整的，并且不按照18S-5.8S-28S rRNA基因顺序排列，也没有多个完整拷贝顺序排列的区域。这提示贾第虫rRNA基因可能是以一种不同于典型真核生物的方式聚集的。因此本文认为以上这些特点可能与贾第虫不能形成典型核仁结构有关。 2）本文从贾第虫基因组中鉴定出了5S rRNA基因，并实验验证了其表达及其完整基因序列所编码的5S rRNA具有典型真核生物的T型二级结构，且具有绝大多数保守位点。RT-PCR表明该基因具有转录活性。该结果否定了前人的贾第虫没有5S rRNA的实验结果。并表明贾第虫尽管很原始，但其5S rRNA基因仍然是独立存在的和单独转录的。贾第虫基因组中总共有8个5S rRNA基因拷贝（且其中还有一个拷贝具有15个bp的异常插入）这大大低于一般真核生物的拷贝数。这些5S rRNA基因也不形成串联排列的区域。 我们还在贾第虫中鉴定出在真核生物中唯一与5S rRNA接触的核糖体蛋白L5蛋白并验证了其表达，该序列与其他真核生物的L5蛋白相似性很高，这提示贾第虫在5S rRNA基因转录出核后与L5蛋白结合形成5S RNP的过程可能与典型的真核生物是一致的。此外，我们从贾第虫中鉴定不出符合典型真核生物TFIIIA因子特征的蛋白，这提示贾第虫5S rRNA的转录起始以及转录后出核的机制可能与典型真核生物不同。过去对贾第虫的研究表明高等真核生物里RNA聚合酶III所独有的四个亚基在贾第虫中找不到同源物，而这样不完整的RNA聚合酶III已经可以在贾第虫中完成5S rRNA的转录了，这表明RNA聚合酶III所独有的这些亚基可能是为了完成其他功能而进化出来的。

Differences in the rDNA-bearing chromosome divide the Asian-Pacific and Atlantic species of Crassostrea (Bivalvia, Mollusca)

Karyotype and chromosomal location of the major ribosomal RNA genes (rDNA) were studied using fluorescence in situ hybridization (FISH) in five species of Crassostrea: three Asian-Pacific species (C. gigas, C. plicatula, and C. ariakensis) and two Atlantic species (C. virginica and C. rhizophorae). FISH probes were made by PCR amplification of the intergenic transcribed spacer between the 18S and 5.8S rRNA genes, and labeled with digoxigenin-11-dUTP. All five species had a haploid number of 10 chromosomes. The Atlantic species had 1-2 submetacentric chromosomes, while the three Pacific species had none. FISH with metaphase chromosomes detected a single telomeric locus for rDNA in all five species without any variation. In all three Pacific species, rDNA was located on the long arm of Chromosome 10 (10q)-the smallest chromosome. In the two Atlantic species, rDNA was located on the short arm of Chromosome 2 (2p)-the second longest chromosome. A review of other studies reveals the same distribution of NOR sites (putative rDNA loci) in three other species: on 10q in C. sikamea and C. angulata from the Pacific Ocean and on 2p in C. gasar from the western Atlantic. All data support the conclusion that differences in size and shape of the rDNA-bearing chromosome represent a major divide between Asian-Pacific and Atlantic species of Crassostrea. This finding suggests that chromosomal divergence can occur under seemingly conserved karyotypes and may play a role in reproductive isolation and speciation.

Phylogenetic relationships of five species of Dorippinae (Crustacea, Decapoda) revealed by 16S rDNA sequence analysis

A molecular phylogeny is presented for the subfamily Dorippinae (including 9 individuals, representing 5 species and 4 genera), based on the sequence data from 16S rRNA gene. Two-cluster test between lineages in these phylogenetic trees has been performed. On the basis of rate constancy, the rate of nucleotide substitutions of 16S rDNA sequence data is estimated as 0.27% per million years. The analysis strongly supports the recognition of the Dorippinae as a monophyletic subfamily. Phylogenetic tree indicates that the subfamily Dorippinae is divided into two main clades, and genus Dorippe appears basal in the subfamily, diverging from other species 36.6 Ma ago. It is also clear that the Heikea is closely related to the genus Neodorippe. The divergence time between them is 15.8 Ma.