Karyotype of the invasive species Pterois volitans (Scorpaeniformes: Scorpaenidae) from Margarita Island, Venezuela

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic characterization of the Passiflora edulis Sims x Passiflora cincinnata Mast. interspecific hybrid and its parents.

The genus Passiflora L. consists of approximately 530 widely distributed species, including Passiflora edulis, which has drawn interest because of its commercial and agronomic value. Passiflora cincinnata is another important species owing to its long flowering period and resistance or tolerance to diseases and pests. In the present study, the meiotic segregation and pollen viability of an interspecific hybrid (P. edulis x P. cincinnata) and its parents were analyzed. The genomic contents were characterized using chromomycin A3 (CMA3)/40-60-diamidino-2-phenylindole (DAPI) staining, fluorescent in situ hybridization with 5S/45S ribosomal DNA (rDNA), genomic in situ hybridization (GISH), and inter-simple sequence repeat (ISSR) markers. The results indicated the diploid chromosome number for the parents and interspecific hybrid was 2n = 18. We also observed regular meiosis, one pair of S rDNA sites, and two pairs of 45S rDNA sites that colocalized with two pairs of CMA3 /DAPI- bands. The GISH data revealed three distinct chromosomal groups in the hybrid. The genetic origins of the interspecific hybrid, and its relationship with its parents were also confirmed using ISSR markers.

Patterns of rDNA and telomeric sequences diversification: contribution to repetitive DNA organization in Phyllostomidae bats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Assessment of prey overlap between a native (Polistes humilis) and an introduced (Vespula germanica) social wasp using morphology and phylogenetic analyses of 16S rDNA

In newly invaded communities, interspecific competition is thought to play an important role in determining the success of the invader and its impact on the native community. In southern Australia, the native Polistes humilis was the predominant social wasp prior to the arrival of the exotic Vespula germanica (Hymenoptera: Vespidae). Both species forage for similar resources (water, pulp, carbohydrate and protein prey), and concerns have arisen about potential competition between them. The aim of this study was to identify the protein foods that these wasps feed on. As many prey items are masticated by these wasps to the degree that they cannot be identified using conventional means, morphological identification was complemented by sequencing fragments of the mitochondrial 16S rRNA gene. GenBank searches using blast and phylogenetic analyses were used to identify prey items to at least order level. The results were used to construct complete prey inventories for the two species. These indicate that while P. humilis is restricted to feeding on lepidopteran larvae, V. germanica collects a variety of prey of invertebrate and vertebrate origin. Calculated values of prey overlap between the two species are used to discuss the implications of V. germanica impacting on P. humilis. Results obtained are compared to those gained by solely 'conventional' methods, and the advantages of using DNA-based taxonomy in ecological studies are emphasized.

Transposable elements in a marginal plant population

Background
How new forms arise in nature has engaged evolutionary biologists since Darwin's seminal treatise on the origin of species. Transposable elements (TEs) may be among the most important internal sources for intraspecific variability. Thus, we aimed to explore the temporal dynamics of several TEs in individual genotypes from a small, marginal population of Aegilops speltoides. A diploid cross-pollinated grass species, it is a wild relative of the various wheat species known for their large genome sizes contributed by an extraordinary number of TEs, particularly long terminal repeat (LTR) retrotransposons. The population is characterized by high heteromorphy and possesses a wide spectrum of chromosomal abnormalities including supernumerary chromosomes, heterozygosity for translocations, and variability in the chromosomal position or number of 45S and 5S ribosomal DNA (rDNA) sites. We propose that variability on the morphological and chromosomal levels may be linked to variability at the molecular level and particularly in TE proliferation.

Results
Significant temporal fluctuation in the copy number of TEs was detected when processes that take place in small, marginal populations were simulated. It is known that under critical external conditions, outcrossing plants very often transit to self-pollination. Thus, three morphologically different genotypes with chromosomal aberrations were taken from a wild population of Ae. speltoides, and the dynamics of the TE complex traced through three rounds of selfing. It was discovered that: (i) various families of TEs vary tremendously in copy number between individuals from the same population and the selfed progenies; (ii) the fluctuations in copy number are TE-family specific; (iii) there is a great difference in TE copy number expansion or contraction between gametophytes and sporophytes; and (iv) a small percentage of TEs that increase in copy number can actually insert at novel locations and could serve as a bona fide mutagen.

Conclusions
We hypothesize that TE dynamics could promote or intensify morphological and karyotypical changes, some of which may be potentially important for the process of microevolution, and allow species with plastic genomes to survive as new forms or even species in times of rapid climatic change.

Initiation of transcription of rDNA in rice

Three direct repeats of 320, 340 and 238 nucleotides were detected upstream to the 5′ end of the 18S rRNA gene of an rDNA unit present on a 9.8 kb EcoRT fragment of the rice DNA. The primer extension analysis showed that the site of initiation of transcription is in the 1st repeat at an A, the 623rd nucleotide upstream to the 5′ end of the 18S rRNA gene. Different stretches of the intergenic spacer DNA linked to the Chloramphenicol acetyl transferase gene were transcribed in the intact nuclei of rice embryos. The S1 nuclease protection analysis of the transcripts using [32P]-labelled Chloramphenicol acetyl transferase gene as the probe showed the presence of multiple promoters for rDNA transcription.

松属单维管束亚属植物rDNA的染色体定位研究

松属植物的基因组十分庞大（大于20000Mbp），其中约90%是由重复序列组成的，我们对其结构和组成仍知之甚少。松属在系统分类上分为两个亚属:单维管束亚属和双维管束亚属。基因组大小研究发现单维管束亚属植物的基因组更大。rDNA作为一类有功能的多基因家族重复序列，其自身特性决定了它在基因组研究中的重要性。FISH技术为rDNA在染色体上物理定位提供了有力的工具。尽管现在对松属rDNA FISH已有不少报道，但主要集中在双维管束亚属，对单维管束亚属的研究几乎是空白。本研究选择5个单维管束亚属松属植物P. bungeana, P. koraiensis, P. armandii, P. wallichiana, P. strobus，进行rDNA FISH研究。旨在弄清18S-25S rDNA和5S rDNA在单维管束亚属植物染色体上的位点数目和分布模式。结合前人对松属双维管束亚属植物的工作，对单、双维管束亚属植物之间rDNA FISH结果进行比较，从而可以从整体上认识松属植物的18S-25S rDNA和5S rDNA在染色体上的分布式样。在此基础上进一步探讨18S-25S rDNA和5S rDNA这些重复序列在松属植物基因组结构和组成中的地位和作用。本研究主要结果如下： 1.rDNA FISH在松属染色体核型分析中的作用 本研究中5种松属单维管束亚属植物染色体数目均为2n=24，除最短一条染色体为亚中部着丝粒染色体外，其余11条均为中部着丝粒染色体，长度和臂比也十分接近，同源染色体的不容易鉴定，很难排出精确的核型。在我们的研究结果中，5个松属植物中，除了白皮松外，18S-25S rDNA和5S rDNA分布在12对染色体中的10对染色体上，这些位点可作为染色体标记，大大提高了同源染色体鉴定的准确度，但是染色体之间排序问题依然没有很好地解决。核型比较认为种间是否存在部分同源染色体关系也不是十分明确，仅Ⅺ号和Ⅻ号染色体有这种关系，这主要由于Ⅺ号和Ⅻ号染色体容易准确地鉴别出来。核型分析的精确仍有待增加标记来提高。 2．rDNA位点数目在松属两个亚属间的比较及其与基因组大小的关系 松属植物18S-25S rDNA位点通常为5-10个，5S rDNA位点为1-4个。其中单维管束亚属18S-25S rDNA位点通常为9-10个（除白皮松为4个外），5S rDNA位点为2- 4个;双维管束亚属为18S-25S rDNA位点通常为5-10个，5S rDNA位点通常为1-2个。而二倍体被子植物18S-25S rDNA位点通常为1-5个5S rDNA位点为1-3个。暗示18S-25S rDNA和5S rDNA位点数目多少和基因组大小还是有一定的相关性。因为松属植物的基因组比典型的二倍体被子植物大得多，单维管束亚属植物的的C-值又普遍比双维管束亚属植物的高。白皮松虽有些例外，18S-25S rDNA位点数目少，但信号强度大得多，代表拷贝数高，因此其基因组大小可以从rDNA拷贝数上得到解释。 3．18S-25S rDNA和5S rDNA位点在松属两个亚属之间的分布模式比较 18S-25S rDNA和5S rDNA位点在松属两个亚属染色体上的分布方式有明显不同，每个亚属均有两种分布形式，并形成各自稳定的分布模式。在单维管束植物中，18S-25S rDNA和5S rDNA位点或相邻分布于同一染色体同一臂上，5S rDNA位于臂的远端;或两位点分布于不同的染色体。而在双维管束植物中18S-25S rDNA和5S rDNA或相邻分布于同一染色体同一臂上，18S-25S rDNA在臂的远端;或两位点分布于同一染色体两条臂上。在两个亚属中，当18S-25S rDNA和5S rDNA位点位于同一条染色体臂上时，相对位置正好相反。这完全不同的rDNA分布模式的形成，可能与松属这两个亚属植物的物种形成和分化过程中染色体发生倒位或易位有关，暗示这两个亚属的基因组结构存在分化。但这各自的分布模式是否可以作为判断亚属的特征依据仍有待加大样本量证实。 4．rDNA 位点分布及变异具有系统学意义 rDNA FISH 结果符合分类中亲缘关系越近，分布模式越相似的原则，因而认为rDNA 位点在染色体上的分布模式，具有系统学意义。基于已知的松属植物rDNA FISH结果构建的系统关系，符合传统分类系统中对亚组划分。rDNA FISH结果与分子系统学的研究结果相比较认为，松属单维管亚属5种松中，以乔松和北美乔松关系最近，与同一个亚组的华山松稍远，与另一个亚组的红松更远。而白皮松作为一个特有的孑遗类群，系统位置比较特殊，分子系统学研究认为其处于基部的位置，本研究表明其rDNA位点有明显的特点：位点数目少，但信号强，反映了拷贝数多。那是否它就代表了祖先类群的位点分布模式，需要更多的基部类群的rDNA FISH结果支持。

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.

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。

Distribution of rDNA in the nucleus of Giardia lamblia - Detection by Ag-I silver stain

OBJECTIVE: To determine whether rDNA of Giardia lamblia forms a nucleolus organizer region (NOR)-like structure and is in a very primitive state. STUDY DESIGN: G lamblia was used as the experimental animal, with Euglena gracilis as the control. The distribution was demonstrated indirectly by the modified Ag-I silver technique, which can specifically indicate the NOR under both light and electron microscopes. RESULTS: In the ultrathin sections of silver-stained Euglena cells, all the silver grains were concentrated in the fibrosa of the nucleolus, while no grains found in the cytoplasm, nucleoplasm, condensed chromosomes or pars granulosa of the nucleus. In the silver-stained Giardia cells, no nucleolus was found; a few silver grains were scattered in the nucleus but were not concentrated in any specific region. CONCLUSION: The distribution of silver grains in G lamblia showed that the transcription of rDNA occurs inside the nucleus, though no nucleolus is present. It is possible that chromosomes are in a very primitive state in diplomonad cells; as each chromosome has few prRNA genes, the transcription is independent of a nucleolus. These results imply that the rDNA of Giardia does not form a NOR-like structure and seems to represent a very primitive state in the evolution of the nucleolus.

Dynamic regulation of ARGONAUTE4 within multiple nuclear bodies in Arabidopsis thaliana.

DNA methylation directed by 24-nucleotide small RNAs involves the small RNA-binding protein ARGONAUTE4 (AGO4), and it was previously shown that AGO4 localizes to nucleolus-adjacent Cajal bodies, sites of snRNP complex maturation. Here we demonstrate that AGO4 also localizes to a second class of nuclear bodies, called AB-bodies, which are found immediately adjacent to condensed 45S ribosomal DNA (rDNA) sequences. AB-bodies also contain other proteins involved in RNA-directed DNA methylation including NRPD1b (a subunit of the RNA Polymerase IV complex, RNA PolIV), NRPD2 (a second subunit of this complex), and the DNA methyltransferase DRM2. These two classes of AGO4 bodies are structurally independent--disruption of one class does not affect the other--suggesting a dynamic regulation of AGO4 within two distinct nuclear compartments in Arabidopsis. Abolishing Cajal body formation in a coilin mutant reduced overall AGO4 protein levels, and coilin dicer-like3 double mutants showed a small decrease in DNA methylation beyond that seen in dicer-like3 single mutants, suggesting that Cajal bodies are required for a fully functioning DNA methylation system in Arabidopsis.

探讨rDNA ITS区作为果蝇Drosophila nasuta分子系统发育研究的价值

国家自然科学基金;中国科学院基金