Orosová, Martina; Ivica, Králová-Hromadová; Eva, Bazsalovicsová; Marta, Spakulová
Karyotype and chromosomal characteristics, i.e. number and location of ribosomal DNA (rDNA) clusters, and sequence variation of the ribosomal internal transcribed spacer 2 (ITS2) were studied in a monozoic (unsegmented) tapeworm, Caryophyllaeides fennica (Caryophyllidea), using conventional and Ag-staining, fluorescent in situ hybridization (FISH) with 18S rDNA probe, and PCR amplification, cloning and sequencing of the complete ribosomal ITS2 spacer. The karyotype of this species was composed of ten pairs of metacentric (m) chromosomes (2n=20). All chromosomes except the pair No. 2 displayed DAPI-positive heterochromatin in centromeric regions. In addition, two distinct interstitial DAPI-positive bands were identified on chromosome pair No. 7. FISH with 18S rDNA probe revealed four clusters of major ribosomal genes situated in the pericentromeric region of the short arms in two pairs of metacentric chromosomes Nos. 8 and 9. Hybridization signals were stronger in the pair No. 8, indicating a higher amount of rDNA repeats at this nucleolar organizer region (NOR). Analysis of 15 ITS2 rDNA sequences (five recombinant clones from each of three individuals) showed 13 structurally different ribotypes, distinguished by 26 nucleotide substitutions and variable numbers and combinations of short repetitive motifs that allowed sorting the sequences into four ITS2 variants. These results contribute to recently published evidence for the intraindividual ribosomal ITS sequence variability in basal tapeworms with multiple rDNA loci and imply that both phenomena may be mutually linked.
Yu, Shoukai; Lemos, Bernardo
Ribosomal RNAs (rRNAs) account for >60% of all RNAs in eukaryotic cells and are encoded in the ribosomal DNA (rDNA) arrays. The rRNAs are produced from two sets of loci: the 5S rDNA array resides exclusively on human chromosome 1, whereas the 45S rDNA array resides on the short arm of five human acrocentric chromosomes. The 45S rDNA gives origin to the nucleolus, the nuclear organelle that is the site of ribosome biogenesis. Intriguingly, 5S and 45S rDNA arrays exhibit correlated copy number variation in lymphoblastoid cells (LCLs). Here we examined the genomic architecture and repeat content of the 5S and 45S rDNA arrays in multiple human genome assemblies (including PacBio MHAP assembly) and ascertained contacts between the rDNA arrays and the rest of the genome using Hi-C datasets from two human cell lines (erythroleukemia K562 and lymphoblastoid cells). Our analyses revealed that 5S and 45S arrays each have thousands of contacts in the folded genome, with rDNA-associated regions and genes dispersed across all chromosomes. The rDNA contact map displayed conserved and disparate features between two cell lines, and pointed to specific chromosomes, genomic regions, and genes with evidence of spatial proximity to the rDNA arrays; the data also showed a lack of direct physical interaction between the 5S and 45S rDNA arrays. Finally, the analysis identified an intriguing organization in the 5S array with Alu and 5S elements adjacent to one another and organized in opposite orientation along the array. Portraits of genome folding centered on the ribosomal DNA array could help understand the emergence of concerted variation, the control of 5S and 45S expression, as well as provide insights into an organelle that contributes to the spatial localization of human chromosomes during interphase. PMID:27797956
Zhou, Hong; Wang, Yapei; Lv, Qiongying; Zhang, Juan; Wang, Qing; Gao, Fei; Hou, Haoli; Zhang, Hao; Zhang, Wei; Li, Lijia
The ribosomal RNA (rRNA) gene encodes rRNA for protein synthesis. Aberrant expression of the rRNA gene has been generally observed in tumor cells and levels of its promoter methylation as an epigenetic regulator affect rRNA gene transcription. The possible relationship between expression and promoter methylation of rDNA has not been examined in human clinical cervical cancer. Here we investigate rRNA gene expression by quantitative real time PCR, and promoter methylation levels by HpaII/MspI digestion and sodium bisulfite sequencing in the development of human cervical cancer. We find that indeed rRNA levels are elevated in most of cervical intraepithelial neoplasia (CIN) specimens as compared with non-cancer tissues. The rDNA promoter region in cervical intraepithelial neoplasia (CIN) tissues reveals significant hypomethylation at cytosines in the context of CpG dinucleotides, accompanied with rDNA chromatin decondensation. Furthermore treatment of HeLa cells with the methylation inhibitor drug 5-aza-2’-deoxycytidine (DAC) demonstrates the negative correlation between the expression of 45S rDNA and the methylation level in the rDNA promoter region. These data suggest that a decrease in rDNA promoter methylation levels can result in an increase of rRNA synthesis in the development of human cervical cancer. PMID:27695092
Cluster, P. D.; Allard, R. W.
DNA samples from 980 plants of Avena barbata from 48 ecologically diverse sites in California and Oregon were assayed to determine their genotype for two duplicated loci governing rDNA variants. More than 40 different rDNA genotypes were observed among which 5 made up 96% of our sample in environmentally homogeneous sites; predominant genotypes were less frequent and recombinant genotypes were more frequent in environmentally heterogeneous sites. The spatial distribution of each predominant rDNA genotype was nearly an exact overlay on both macro- and microgeographical scales of a distinctive habitat and also of the distribution of an eight-locus morphological-allozyme variant genotype. In all, seven different habitat-genotype combinations (ecotypes) were distinguishable on the basis of their morphological-allozyme-rDNA genotypes. None of these seven genotypes has been found in ancestral Spanish populations; thus the above predominant multilocus genotypes (ecotypes) of the colonial populations evidently evolved subsequent to the recent introduction (within 150-200 generations) of A. barbata to California. The precise associations of specific alleles and genotypes of the morphological allozyme and rDNA loci with different specifiable habitats leads us to the conclusion that natural selection favoring particular multilocus combinations of alleles in different habitats was the main guiding force in shaping the internal genetic structure of local populations as well as the overall adaptive landscape of A. barbata over California and Oregon. PMID:7713443
Allard, R. W.; Maroof, MAS.; Zhang, Q.; Jorgensen, R. A.
Twenty rDNA spacer-length variants (slvs) have been identified in barley. These slvs form a ladder in which each variant (with one exception) differs from its immediate neighbors by a 115-bp subrepeat. The 20 slvs are organized in two families, one forming an eight-step ladder (slvs 100-107) in the nucleolus organizer region (NOR) of chromosome 7 and the other a 12-step ladder (slvs 108a-118) in the NOR of chromosome 6. The eight shorter slvs (100-107) segregate and serve as markers of eight alleles of Mendelian locus Rrn2 and the 12 longer slvs (108a-118) segregate and serve as markers of 12 alleles of Mendelian locus Rrn1. Most barley plants (90%) are homozygous for two alleles, including one from each the 100-107 and the 108a-118 series. Two types of departures from this typical pattern of molecular and genetic organization were identified, one featuring compound alleles marked by two slvs of Rrn1 or of Rrn2, and the other featuring presence in Rrn1 of alleles normally found in Rrn2, and vice versa. The individual and joint effects on adaptedness of the rDNA alleles are discussed. It was concluded that selection acting on specific genotypes plays a major role in molding the strikingly different allelic and genotypic frequency distributions seen in populations of wild and cultivated barley from different ecogeographical regions. PMID:2249766
Yang, Mingsheng; Zhang, Yalin
The tribe Satyrini is one of the most diverse groups of butterflies, but no robust phylogenetic hypothesis for this group has been achieved. Two rarely used 16s and 28s ribosomal and another seven protein-coding genes were used to reconstruct the phylogeny of the Satyrini, with further aim to evaluate the informativeness of the ribosomal genes. Our maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) analyses consistently recovered three well-supported clades for the eleven sampled subtribes of Satyrini: clade I includes Eritina and Coenonymphina, being sister to the clade II + clade III; clade II contains Parargina, Mycalesina and Lethina, and the other six subtribes constitute clade III. The placements of the taxonomically unstable Davidina Oberthür and geographically restricted Paroeneis Moore in Satyrina are confirmed for the first time based on molecular evidence. The close relationships of Callerebia Butler, Loxerebia Watkins and Argestina Riley are well-supported. We suggest that Rhaphicera Butler belongs to Lethina. The partitioned Bremer support (PBS) values of MP analysis show that the 16s rDNA contributes well to the nodes representing all the taxa from subtribe to species levels, and the 28s rDNA is informative at the subtribe level. Furthermore, our ML analyses show that the ribosomal genes 16s rDNA and 28s rDNA are informative, because most node support values are lower in the ML tree after the removal of them than that in ML tree constructed based on the full nine-gene dataset. This indicates that some other ribosomal genes should be tentatively used through combining with traditionally used protein-coding genes in further analysis on phylogeny of Satyrini, providing that proper representatives are sampled.
Lagacé, L.; Pitre, M.; Jacques, M.; Roy, D.
The bacterial community of maple sap was characterized by analysis of samples obtained at the taphole of maple trees for the 2001 and 2002 seasons. Among the 190 bacterial isolates, 32 groups were formed according to the similarity of the banding patterns obtained by amplified ribosomal DNA restriction analysis (ARDRA). A subset of representative isolates for each ARDRA group was identified by 16S rRNA gene fragment sequencing. Results showed a wide variety of organisms, with 22 different genera encountered. Pseudomonas and Ralstonia, of the γ- and β-Proteobacteria, respectively, were the most frequently encountered genera. Gram-positive bacteria were also observed, and Staphylococcus, Plantibacter, and Bacillus were the most highly represented genera. The sampling period corresponding to 50% of the cumulative sap flow percentage presented the greatest bacterial diversity according to its Shannon diversity index value (1.1). γ-Proteobacteria were found to be dominant almost from the beginning of the season to the end. These results are providing interesting insights on maple sap microflora that will be useful for further investigation related to microbial contamination and quality of maple products and also for guiding new strategies on taphole contamination control. PMID:15066796
Radeva, Galina; Selenska-Pobell, Sonja
Bacterial diversity was assessed in water samples collected from several uranium mining wastes in Ger many and in the United States by using 16S rDNA and ribosomal intergenic spacer amplification retrievals. The results obtained using the 16S rDNA retrieval showed that the samples collected from the uranium mill tailings of Schlema/Alberoda, Germany, were predominated by Nitrospina-like bacteria, whereas those from the mill tailings of Shiprock, New Mexico, USA, were predominated by gamma-Pseudomonas and Frauteria spp. Additional smaller populations of the Cytophaga-Flavobacterium-Bacteroides group and alpha- and delta-Proteobacteria were identified in the Shiprock samples as well. Proteobacteria and Cytophaga-Flavobacterium-Bacteroides were also found in the third uranium mill tailings studied, Gittersee/Coschütz, Germany, but the groups of the predominant clones were rather small. Most of the clones of the Gittersee/Coschütz samples represented individual sequences, which indicates a high level of bacterial diversity. The samples from the fourth uranium waste studied, Steinsee Deponie B1, Germany, were predominantly occupied by Acinetobacter spp. The ribosomal intergenic spacer amplification retrieval provided results complementary to those obtained by the 16S rDNA analyses. For instance, in the Shiprock samples, an additional predominant bacterial group was identified and affiliated with Nitrosomonas sp., whereas in the Gittersee/Coschütz samples, anammox populations were identified that were not retrieved by the applied 16S rDNA approach.
Bellavia, Daniele; Dimarco, Eufrosina; Caradonna, Fabio
We previously reported the characterization 5S ribosomal DNA (rDNA) clusters in the common sea urchin Paracentrotus lividus and demonstrated the presence of DNA methylation-dependent silencing of embryo specific 5S rDNA cluster in adult tissue. In this work, we show genetic and epigenetic characterization of 18S-26S rDNA clusters in this specie. The results indicate the presence of three different 18S-26S rDNA clusters with different Non-Transcribed Spacer (NTS) regions that have different chromosomal localizations. Moreover, we show that the two largest clusters are hyper-methylated in the promoter-containing NTS regions in adult tissues, as in the 5S rDNA. These findings demonstrate an analogous epigenetic regulation in small and large rDNA clusters and support the logical synchronism in building ribosomes. In fact, all the ribosomal RNA genes must be synchronously and equally transcribed to perform their unique final product.
microgametes are released from one microgametocyte during exflagellation while only one female macrogamete differentiates from a macrogametocyte...protein synthesis. In contrast to other eukaryotes, the rRNA genes in Plasmodium species are unique in terms of their genomic arrangement and...development and evolution. In this study, three structurally distinct rRNA genes, including one novel" type, have been characterized from the genomic DNA of
Xu, Jiru; Moore, John E; Millar, B Cherie
The aim of the investigation reported in this paper was to identify the bacterial microflora on monetary coinage from 17 countries by employment of polymerase chain reaction (PCR) sequenced-based molecular identification of rDNA from bacterial cultures. Silver, bronze, and other alloy coins (approximately 300 g) from 17 currencies were enriched individually by aerobic culturing in tryptone soya broth for 72 hours at 30 degrees C. Next, 20 microL of broth was inoculated onto Columbia blood agar supplemented with 5 percent volume-pervolume (v/v) defibrinated horse blood for 72 hours at 30 degrees C, and resulting colonies were purified by further subculture, as detailed above, for a further 72 hours. All colonies were identified by initial PCR amplification of a partial region of the 16S rDNA gene locus, which was then sequenced, and the sequence was aligned according to the BLASTn algorithm. Twenty-five isolates were obtained from the coinage; of these, 25 (100 percent) were Gram positive, and the most prevalent genus observed was Bacillus (B. megaterium, B. lentus, B. litoralis, B. subtilis, B. circulans and other Bacillus spp.), which accounted for 10 of 25 isolates (40 percent) and was isolated from 10 of 17 countries (58.8 percent). It was followed in prevalence by Staphylococcus spp. (Staph. aureus, Staph. epidermidis, Staph. hominis, Staph. schleiferi), which accounted for 7 of 25 isolates (28 percent) and were isolated from 7 of 17 countries (41.2 percent). Given the organisms identified in this study, it is not believed that monetary coinage presents any particular risk to public health. The authors support the principles of basic hygiene, however, in terms of proper handwashing and the avoidance of handling money when working with food or dressing wounds and skin lesions, In conclusion, the study demonstrated that money from 17 countries was contaminated by environmental Gram-positive flora, in particular Bacillus spp., and that the universal 16S rDNA
Background In flowering plants and animals the most common ribosomal RNA genes (rDNA) organisation is that in which 35S (encoding 18S-5.8S-26S rRNA) and 5S genes are physically separated occupying different chromosomal loci. However, recent observations established that both genes have been unified to a single 35S-5S unit in the genus Artemisia (Asteraceae), a genomic arrangement typical of primitive eukaryotes such as yeast, among others. Here we aim to reveal the origin, distribution and mechanisms leading to the linked organisation of rDNA in the Asteraceae by analysing unit structure (PCR, Southern blot, sequencing), gene copy number (quantitative PCR) and chromosomal position (FISH) of 5S and 35S rRNA genes in ~200 species representing the family diversity and other closely related groups. Results Dominant linked rDNA genotype was found within three large groups in subfamily Asteroideae: tribe Anthemideae (93% of the studied cases), tribe Gnaphalieae (100%) and in the "Heliantheae alliance" (23%). The remaining five tribes of the Asteroideae displayed canonical non linked arrangement of rDNA, as did the other groups in the Asteraceae. Nevertheless, low copy linked genes were identified among several species that amplified unlinked units. The conserved position of functional 5S insertions downstream from the 26S gene suggests a unique, perhaps retrotransposon-mediated integration event at the base of subfamily Asteroideae. Further evolution likely involved divergence of 26S-5S intergenic spacers, amplification and homogenisation of units across the chromosomes and concomitant elimination of unlinked arrays. However, the opposite trend, from linked towards unlinked arrangement was also surmised in few species indicating possible reversibility of these processes. Conclusions Our results indicate that nearly 25% of Asteraceae species may have evolved unusual linked arrangement of rRNA genes. Thus, in plants, fundamental changes in intrinsic structure of rDNA units
Griffin, John N.; Sondalle, Samuel B.; del Viso, Florencia; Baserga, Susan J.; Khokha, Mustafa K.
The production of ribosomes is ubiquitous and fundamental to life. As such, it is surprising that defects in ribosome biogenesis underlie a growing number of symptomatically distinct inherited disorders, collectively called ribosomopathies. We previously determined that the nucleolar protein, NOL11, is essential for optimal pre-rRNA transcription and processing in human tissue culture cells. However, the role of NOL11 in the development of a multicellular organism remains unknown. Here, we reveal a critical function for NOL11 in vertebrate ribosome biogenesis and craniofacial development. Nol11 is strongly expressed in the developing cranial neural crest (CNC) of both amphibians and mammals, and knockdown of Xenopus nol11 results in impaired pre-rRNA transcription and processing, increased apoptosis, and abnormal development of the craniofacial cartilages. Inhibition of p53 rescues this skeletal phenotype, but not the underlying ribosome biogenesis defect, demonstrating an evolutionarily conserved control mechanism through which ribosome-impaired craniofacial cells are removed. Excessive activation of this mechanism impairs craniofacial development. Together, our findings reveal a novel requirement for Nol11 in craniofacial development, present the first frog model of a ribosomopathy, and provide further insight into the clinically important relationship between specific ribosome biogenesis proteins and craniofacial cell survival. PMID:25756904
Son, Ora; Kim, Sunghan; Shin, Yun-jeong; Kim, Woo-Young; Koh, Hee-Jong; Cheon, Choong-Ill
The ribosomal protein S6 (RPS6) is a downstream component of the signaling mediated by the target of rapamycin (TOR) kinase that acts as a central regulator of the key metabolic processes, such as protein translation and ribosome biogenesis, in response to various environmental cues. In our previous study, we identified a novel role of plant RPS6, which negatively regulates rDNA transcription, forming a complex with a plant-specific histone deacetylase, AtHD2B. Here we report that the Arabidopsis RPS6 interacts additionally with a histone chaperone, nucleosome assembly protein 1(AtNAP1;1). The interaction does not appear to preclude the association of RPS6 with AtHD2B, as the AtNAP1 was also able to interact with AtHD2B as well as with an RPS6-AtHD2B fusion protein in the BiFC assay and pulldown experiment. Similar to a positive effect of the ribosomal S6 kinase 1 (AtS6K1) on rDNA transcription observed in this study, overexpression or down regulation of the AtNAP1;1 resulted in concomitant increase and decrease, respectively, in rDNA transcription suggesting a positive regulatory role played by AtNAP1 in plant rDNA transcription, possibly through derepression of the negative effect of the RPS6-AtHD2B complex. - Highlights: • Nucleosome assembly protein 1 (AtNAP1) interacts with RPS6 as well as with AtHD2B. • rDNA transcription is regulated S6K1. • Overexpression or down regulation of AtNAP1 results in concomitant increase or decrease in rDNA transcription.
Naganowska, Barbara; Zielińska, Anna
Double-target fluorescent in situ hybridization (FISH) was used to determine the genomic distribution of ribosomal RNA genes in five Lupinus species: L. cosentinii (2n=32), L. pilosus (2n=42), L. angustifolius (2n=40), L. luteus (2n=52) and L. mutabilis (2n=48). 18S-25S rDNA and 5S rDNA were used as probes. Some interspecific variation was observed in the number and size of the 18S-25S rDNA loci. All the studied species had one chromosome pair carrying 5S rDNA.
Abirached-Darmency, Mona; Prado-Vivant, Emilce; Chelysheva, Liudmila; Pouthier, Thomas
Within Fabaceae, legume species have a variable genome size, chromosome number, and ploidy level. The genome distribution of ribosomal genes, easily detectable by fluorescent in situ hybridization (FISH), is a good tool for anchoring physical and genetic comparative maps. The organisation of 45S rDNA and 5S loci was analysed by FISH in the 4 closely related species: Pisum sativum, Medicago truncatula, Medicago sativa (2 diploid taxa), and Lathyrus sativus. The 2 types of rDNA arrays displayed interspecific variation in locus number and location, but little intraspecific variation was detected. In the model legume, M. truncatula, the presence of 2 adjacent 45S rDNA loci was demonstrated, and the location of the rDNA loci was independent of the general evolution of the genome DNA. The different parameters relative to clustering of the rDNA loci in specific chromosome regions and the possible basis of rDNA instability are discussed.
Intra-individual internal transcribed spacer 1 (ITS1) and ITS2 ribosomal sequence variation linked with multiple rDNA loci: a case of triploid Atractolytocestus huronensis, the monozoic cestode of common carp.
Králová-Hromadová, Ivica; Stefka, Jan; Spakulová, Marta; Orosová, Martina; Bombarová, Marta; Hanzelová, Vladimíra; Bazsalovicsová, Eva; Scholz, Tomás
Complete sequences of the ribosomal internal transcribed spacers (ITS1 and ITS2) and karyological characters of the monozoic (unsegmented) tapeworm Atractolytocestus huronensis Anthony, 1958 (Cestoda: Caryophyllidea) from Slovakia were analysed, revealing considerable intra-genomic variability and triploidy in all analysed specimens. Analysis of 20 sequences of each ITS1 and ITS2 spacer yielded eight and 10 different sequence types, respectively. In individual tapeworms, two to four ITS1 and three to four ITS2 sequence types were found. Divergent intra-genomic ITS copies were mostly induced by nucleotide substitutions and different numbers of short repetitive motifs within the sequence. In addition, triploidy was found to be a common feature of A. huronensis. The karyotype of Slovakian A. huronensis possesses three sets of chromosomes (3n=24, n=4m+3st+1minute chromosome), similar to the previously described triploidy in conspecific tapeworms from North America. Fluorescent in situ hybridisation (FISH) with a ssrDNA probe revealed two distinct rDNA clusters for each homologue of the triplet number 2. To date, A. huronensis is the only cestode species in which intra-individual ITS sequence variants were found in parallel with its triploid nature and multiple rDNA loci. Some of these molecular and genetic features were observed in several other species of basal or nearly basal tapeworms of the orders Caryophyllidea and Diphyllobothriidea, which indicates that the phenomena may be characteristic for evolutionarily lower tapeworms and deserve more attention in future studies.
Rosato, Marcela; Kovařík, Aleš; Garilleti, Ricardo; Rosselló, Josep A.
Genes encoding ribosomal RNA (rDNA) are universal key constituents of eukaryotic genomes, and the nuclear genome harbours hundreds to several thousand copies of each species. Knowledge about the number of rDNA loci and gene copy number provides information for comparative studies of organismal and molecular evolution at various phylogenetic levels. With the exception of seed plants, the range of 45S rDNA locus (encoding 18S, 5.8S and 26S rRNA) and gene copy number variation within key evolutionary plant groups is largely unknown. This is especially true for the three earliest land plant lineages Marchantiophyta (liverworts), Bryophyta (mosses), and Anthocerotophyta (hornworts). In this work, we report the extent of rDNA variation in early land plants, assessing the number of 45S rDNA loci and gene copy number in 106 species and 25 species, respectively, of mosses, liverworts and hornworts. Unexpectedly, the results show a narrow range of ribosomal locus variation (one or two 45S rDNA loci) and gene copies not present in vascular plant lineages, where a wide spectrum is recorded. Mutation analysis of whole genomic reads showed higher (3-fold) intragenomic heterogeneity of Marchantia polymorpha (Marchantiophyta) rDNA compared to Physcomitrella patens (Bryophyta) and two angiosperms (Arabidopsis thaliana and Nicotiana tomentosifomis) suggesting the presence of rDNA pseudogenes in its genome. No association between phylogenetic position, taxonomic adscription and the number of rDNA loci and gene copy number was found. Our results suggest a likely evolutionary rDNA stasis during land colonisation and diversification across 480 myr of bryophyte evolution. We hypothesise that strong selection forces may be acting against ribosomal gene locus amplification. Despite showing a predominant haploid phase and infrequent meiosis, overall rDNA homogeneity is not severely compromised in bryophytes. PMID:27622766
Rosato, Marcela; Kovařík, Aleš; Garilleti, Ricardo; Rosselló, Josep A
Genes encoding ribosomal RNA (rDNA) are universal key constituents of eukaryotic genomes, and the nuclear genome harbours hundreds to several thousand copies of each species. Knowledge about the number of rDNA loci and gene copy number provides information for comparative studies of organismal and molecular evolution at various phylogenetic levels. With the exception of seed plants, the range of 45S rDNA locus (encoding 18S, 5.8S and 26S rRNA) and gene copy number variation within key evolutionary plant groups is largely unknown. This is especially true for the three earliest land plant lineages Marchantiophyta (liverworts), Bryophyta (mosses), and Anthocerotophyta (hornworts). In this work, we report the extent of rDNA variation in early land plants, assessing the number of 45S rDNA loci and gene copy number in 106 species and 25 species, respectively, of mosses, liverworts and hornworts. Unexpectedly, the results show a narrow range of ribosomal locus variation (one or two 45S rDNA loci) and gene copies not present in vascular plant lineages, where a wide spectrum is recorded. Mutation analysis of whole genomic reads showed higher (3-fold) intragenomic heterogeneity of Marchantia polymorpha (Marchantiophyta) rDNA compared to Physcomitrella patens (Bryophyta) and two angiosperms (Arabidopsis thaliana and Nicotiana tomentosifomis) suggesting the presence of rDNA pseudogenes in its genome. No association between phylogenetic position, taxonomic adscription and the number of rDNA loci and gene copy number was found. Our results suggest a likely evolutionary rDNA stasis during land colonisation and diversification across 480 myr of bryophyte evolution. We hypothesise that strong selection forces may be acting against ribosomal gene locus amplification. Despite showing a predominant haploid phase and infrequent meiosis, overall rDNA homogeneity is not severely compromised in bryophytes.
Zhao, Ya-E; Wu, Li-Ping; Hu, Li; Xu, Yang; Wang, Zheng-Hang; Liu, Wen-Yan
Due to the difficulty of DNA extraction for Demodex, few studies dealt with the identification and the phyletic evolution of Demodex at molecular level. In this study, we amplified, sequenced, and analyzed a complete (Demodex folliculorum) and an almost complete (D12 missing) (Demodex brevis) ribosomal DNA (rDNA) sequence and also analyzed the primary sequences of divergent domains in small-subunit ribosomal RNA (rRNA) of 51 species and in large-subunit rRNA of 43 species from four superfamilies in Acari (Cheyletoidea, Tetranychoidea, Analgoidea, and Ixodoidea). The results revealed that 18S rDNA sequence was relatively conserved in rDNA-coding regions and was not evolving as rapidly as 28S rDNA sequence. The evolutionary rates of transcribed spacer regions were much higher than those of the coding regions. The maximum parsimony trees of 18S and 28S rDNA appeared to be almost identical, consistent with their morphological classification. Based on the fact that the resolution capability of sequence length and the divergence of the 13 segments (D1-D6, D7a, D7b, and D8-D12) of 28S rDNA were stronger than that of the nine variable regions (V1-V9) of 18S rDNA, we were able to identify Demodex (Cheyletoidea) by the indels occurring in D2, D6, and D8.
Xu, Yan-Hao; Yang, Fei; Cheng, You-Lin; Ma, Lu; Wang, Jian-Bo; Li, Li-Jia
Fluorescence in situ hybridization (FISH) and double FISH experiments were carried out to ascertain the chromosomal distribution patterns of the 45S and 5S ribosomal DNAs in the three species of Cucurbitaceae. Five pairs of 45S rDNA loci and two pairs of 5S rDNA signals were detected on chromosomes of Cucurbita moschata Duch. Luffa cylindrical Roem. contained five pairs of 45S rDNA loci and one pair of 5S rDNA loci. In Benincasa hispida Cogn., two pairs of 45S rDNA sites and one pair of 5S rDNA site were detected. In this species, 5S rDNA and one pair of the 45S loci were collocated closely in chromosome 7S. 45S rDNA chromosomal distribution patterns were highly conserved among the three species, althoufh their number varied markedly. The 5S rDNA sites on chromosomes among the three species were highly polymorphic. We further discussed differentially evolutionary processes of 45S and 5S rDNA in plant genomes.
Madalena, Christiane Rodriguez Gutierrez; Amabis, José Mariano; Stocker, Ann Jacob; Gorab, Eduardo
The chromosomal localization of ribosomal DNA (rDNA) was studied in polytene and diploid tissues of four sciarid species, Trichosia pubescens, Rhynchosciara americana, R. milleri and Schwenkfeldina sp. While hybridization to mitotic chromosomes showed the existence of a single rDNA locus, ribosomal probes hybridized to more than one polytene chromosome region in all the species analyzed as a result of micronucleolar attachment to specific chromosome sites. Micronucleoli are small, round bodies containing transcriptionally active, probably extrachromosomal rDNA. In T. pubescens the rDNA is predominantly localized in chromosome sections X-10 and X-8. In R. americana the rDNA is frequently found associated with centromeric heterochromatin of the chromosomes X, C, B and A, and also with sections X-1 and B-13. Ribosomal probes in R. milleri hybridized with high frequency to pericentric and telomeric regions of its polytene complement. Schwfenkfeldina sp. displays a remarkably unusual distribution of rDNA in polytene nuclei, characterized by the attachment of micronucleoli to many chromosome regions. The results showed that micronucleoli preferentially associate with intercalary or terminal heterochromatin of all sciarid flies analyzed and, depending on the species, are attached to a few (Trichosia), moderate (Rhynchosciara) or a large (Schwenkfeldina sp.) number of polytene chromosome sites.
Huang, Shijiao; Xu, Xiaowei; Wang, Guopeng; Lu, Guoliang; Xie, Wenbing; Tao, Wei; Zhang, Hongyin; Jiang, Qing; Zhang, Chuanmao
RNA-polymerase-I-dependent ribosomal DNA (rDNA) transcription is fundamental to rRNA processing, ribosome assembly and protein synthesis. However, how this process is initiated during the cell cycle is not fully understood. By performing a proteomic analysis of transcription factors that bind RNA polymerase I during rDNA transcription initiation, we identified that the DNA replication initiator Cdc6 interacts with RNA polymerase I and its co-factors, and promotes rDNA transcription in G1 phase in an ATPase-activity-dependent manner. We further showed that Cdc6 is targeted to the nucleolus during late mitosis and G1 phase in a manner that is dependent on B23 (also known as nucleophosmin, NPM1), and preferentially binds to the rDNA promoter through its ATP-binding domain. Overexpression of Cdc6 increases rDNA transcription, whereas knockdown of Cdc6 results in a decreased association of both RNA polymerase I and the RNA polymerase I transcription factor RRN3 with rDNA, and a reduction of rDNA transcription. Furthermore, depletion of Cdc6 impairs the interaction between RRN3 and RNA polymerase I. Taken together, our data demonstrate that Cdc6 also serves as a regulator of rDNA transcription initiation, and indicate a mechanism by which initiation of rDNA transcription and DNA replication can be coordinated in cells.
Zhang, Weimin; Zhao, Guanghou; Luo, Zhouqing; Lin, Yicong; Wang, Lihui; Guo, Yakun; Wang, Ann; Jiang, Shuangying; Jiang, Qingwen; Gong, Jianhui; Wang, Yun; Hou, Sha; Huang, Jing; Li, Tianyi; Qin, Yiran; Dong, Junkai; Qin, Qin; Zhang, Jiaying; Zou, Xinzhi; He, Xi; Zhao, Li; Xiao, Yibo; Xu, Meng; Cheng, Erchao; Huang, Ning; Zhou, Tong; Shen, Yue; Walker, Roy; Luo, Yisha; Kuang, Zheng; Mitchell, Leslie A; Yang, Kun; Richardson, Sarah M; Wu, Yi; Li, Bing-Zhi; Yuan, Ying-Jin; Yang, Huanming; Lin, Jiwei; Chen, Guo-Qiang; Wu, Qingyu; Bader, Joel S; Cai, Yizhi; Boeke, Jef D; Dai, Junbiao
We designed and synthesized a 976,067-base pair linear chromosome, synXII, based on native chromosome XII in Saccharomyces cerevisiae SynXII was assembled using a two-step method, specified by successive megachunk integration and meiotic recombination-mediated assembly, producing a functional chromosome in S. cerevisiae. Minor growth defect "bugs" detected in synXII, caused by deletion of tRNA genes, were rescued by introducing an ectopic copy of a single tRNA gene. The ribosomal gene cluster (rDNA) on synXII was left intact during the assembly process and subsequently replaced by a modified rDNA unit used to regenerate rDNA at three distinct chromosomal locations. The signature sequences within rDNA, which can be used to determine species identity, were swapped to generate a Saccharomyces synXII strain that would be identified as Saccharomyces bayanus by standard DNA barcoding procedures.
Voronov, A S; Shibalev, D V; Kupriianova, N S
A first report on structural organization of ribosomal DNA arrays in some members of the order Squamata is presented. The data obtained point to unusually small (for vertebrates) size of the rDNA repetitive unit (approximately, 10 to 15 kb) in the lizard species examined. Analysis of BAC library of Uta stansburiana (Iguania) showed that haploid genome of this lizard contained a single cluster, consisting of about ten rDNA repeats. Determination of the extent of rDNA unit repetition in some other representatives of the order Squamata, using the method of comparative real-time PCR, showed that the number of rDNA units varied from one or several dozens in Iguanina to several hundred repeats in Scincomorpha and Varonoidea. The results are discussed in terms of an ambiguous position of the family Iguania on the evolutionary trees constructed based on morphological and molecular data.
Fritze, C E; Verschueren, K; Strich, R; Easton Esposito, R
The yeast SIR2 gene maintains inactive chromatin domains required for transcriptional repression at the silent mating-type loci and telomeres. We previously demonstrated that SIR2 also acts to repress mitotic and meiotic recombination between the tandem ribosomal RNA gene array (rDNA). Here we address whether rDNA chromatin structure is altered by loss of SIR2 function by in vitro and in vivo assays of sensitivity to micrococcal nuclease and dam methyltransferase, respectively, and present the first chromatin study that maps sites of SIR2 action within the rDNA locus. Control studies at the MAT alpha locus also revealed a previously undetected MNase-sensitive site at the a1-alpha 2 divergent promoter which is protected in sir2 mutant cells by the derepressed a1-alpha 2 regulator. In rDNA, SIR2 is required for a more closed chromatin structure in two regions: SRR1, the major SIR-Responsive Region in the non-transcribed spacer, and SRR2, in the 18S rRNA coding region. None of the changes in rDNA detected in sir2 mutants are due to the presence of the a1-alpha 2 repressor. Reduced recombination in the rDNA correlates with a small, reproducible transcriptional silencing position effect. Deletion and overexpression studies demonstrate that SIR2, but not SIR1, SIR3 or SIR4, is required for this rDNA position effect. Significantly, rDNA transcriptional silencing and rDNA chromatin accessibility respond to SIR2 dosage, indicating that SIR2 is a limiting component required for chromatin modeling in rDNA. PMID:9351831
Wang, Wencai; Ma, Lu; Becher, Hannes; Garcia, Sònia; Kovarikova, Alena; Leitch, Ilia J; Leitch, Andrew R; Kovarik, Ales
In all eukaryotes, the highly repeated 35S ribosomal DNA (rDNA) sequences encoding 18S-5.8S-26S ribosomal RNA (rRNA) typically show high levels of intragenomic uniformity due to homogenisation processes, leading to concerted evolution of 35S rDNA repeats. Here, we compared 35S rDNA divergence in several seed plants using next generation sequencing and a range of molecular and cytogenetic approaches. Most species showed similar 35S rDNA homogeneity indicating concerted evolution. However, Cycas revoluta exhibits an extraordinary diversity of rDNA repeats (nucleotide sequence divergence of different copies averaging 12 %), influencing both the coding and non-coding rDNA regions nearly equally. In contrast, its rRNA transcriptome was highly homogeneous suggesting that only a minority of genes (<20 %) encode functional rRNA. The most common SNPs were C > T substitutions located in symmetrical CG and CHG contexts which were also highly methylated. Both functional genes and pseudogenes appear to cluster on chromosomes. The extraordinary high levels of 35S rDNA diversity in C. revoluta, and probably other species of cycads, indicate that the frequency of repeat homogenisation has been much lower in this lineage, compared with all other land plant lineages studied. This has led to the accumulation of methylation-driven mutations and pseudogenisation. Potentially, the reduced homology between paralogs prevented their elimination by homologous recombination, resulting in long-term retention of rDNA pseudogenes in the genome.
Paredes, Silvana; Maggert, Keith A.
The rDNA arrays in Drosophila contain the cis-acting nucleolus organizer regions responsible for forming the nucleolus and the genes for the 28S, 18S, and 5.8S/2S RNA components of the ribosomes and so serve a central role in protein synthesis. Mutations or alterations that affect the nucleolus organizer region have pleiotropic effects on genome regulation and development and may play a role in genomewide phenomena such as aging and cancer. We demonstrate a method to create an allelic series of graded deletions in the Drosophila Y-linked rDNA of otherwise isogenic chromosomes, quantify the size of the deletions using real-time PCR, and monitor magnification of the rDNA arrays as their functions are restored. We use this series to define the thresholds of Y-linked rDNA required for sufficient protein translation, as well as establish the rate of Y-linked rDNA magnification in Drosophila. Finally, we show that I-CreI expression can revert rDNA deletion phenotypes, suggesting that double-strand breaks are sufficient to induce rDNA magnification. PMID:19171942
Adams, S P; Leitch, I J; Bennett, M D; Chase, M W; Leitch, A R
All Aloe taxa (∼400 species) share a conserved bimodal karyotype with a basic genome of four large and three small submetacentric/acrocentric chromosomes. We investigated the physical organization of 18S-5.8S-26S and 5S ribosomal DNA (rDNA) using fluorescent in situ hybridization (FISH) to 13 Aloe species. The organization was compared with a phylogenetic tree of 28 species (including the 13 used for FISH) constructed by sequence analysis of the internal transcribed spacer (ITS) of 18S-5.8S-26S rDNA. The phylogeny showed little divergence within Aloe, although distinct, well-supported clades were found. FISH analysis of 5S rDNA distribution showed a similar interstitial location on a large chromosome in all species examined. In contrast, the distribution of 18S-5.8S-26S rDNA was variable, with differences in number, location, and size of loci found between species. Nevertheless, within well-supported clades, all species had the same organizational patterns. Thus, despite the striking stability of karyotype structure and location of 5S rDNA, the distribution of 18S-5.8S-26S rDNA is not so constrained and has clearly changed during Aloe speciation.
Zhukova, A; Prokhorova, E E; Tokmakova, A S; Tsymbalenko, N V; Ataev, G L
The full nucleotide sequences of DNA ribosome cluster of Leucochloridium paradoxum Carus, 1835 and L. perturbatum Pojmanska, 1967 were obtained. rDNA was extracted from 40 isolates of Leucochloridium sp. and analyzed using specific primers. The intraspecific genetically identity of morphologically detected L. paradoxum and L. perturbatum sporocysts was proven. A noticeable interspecific divergence between L. paradoxum and L. perturbatum was indicated. Using rDNA genotyping a case of double infection of snail Succinea sp. with L. paradoxum and L. perturbatum sporocysts was detected.
Teschler, Stefanie; Gotthardt, Julia; Dammann, Gerhard; Dammann, Reinhard H.
Borderline personality disorder (BPD) is a serious psychic disease with a high risk for suicide. DNA methylation is a hallmark for aberrant epigenetic regulation and could be involved in the etiology of BPD. Previously, it has been reported that increased DNA methylation of neuropsychiatric genes is found in the blood of patients with BPD compared to healthy controls. Here, we analyzed DNA methylation patterns of the ribosomal RNA gene (rDNA promoter region and 5′-external transcribed spacer/5′ETS) and the promoter of the proline rich membrane anchor 1 gene (PRIMA1) in peripheral blood samples of 24 female patients (mean age (33 ± 11) years) diagnosed with DSM-IV BPD and in 11 female controls (mean age (32 ± 7) years). A significant aberrant methylation of rDNA and PRIMA1 was revealed for BPD patients using pyrosequencing. For the promoter of PRIMA1, the average methylation of six CpG sites was 1.6-fold higher in BPD patients compared to controls. In contrast, the methylation levels of the rDNA promoter region and the 5′ETS were significantly lower (0.9-fold) in patients with BPD compared to controls. Thus, for nine CpGs located in the rDNA promoter region and for four CpGs at the 5′ETS decreased methylation was found in peripheral blood of patients compared to controls. Our results suggest that aberrant methylation of rDNA and PRIMA1 is associated with the pathogenesis of BPD. PMID:26742039
Gallagher, Renata C.; Blackburn, Elizabeth H.
In the ciliated protozoan Tetrahymena thermophila the ribosomal DNA (rDNA) minichromosome replicates partially under cell cycle control and is also subject to a copy number control mechanism. The relationship between rDNA replication and rRNA gene transcription was investigated by the analysis of replication, transcription, and DNA-protein interactions in a mutant rDNA, the rmm3 rDNA. The rmm3 (for rDNA maturation or maintenance mutant 3) rDNA contains a single-base deletion in the rRNA promoter region, in a phylogenetically conserved sequence element that is repeated in the replication origin region of the rDNA minichromosome. The multicopy rmm3 rDNA minichromosome has a maintenance defect in the presence of a competing rDNA allele in heterozygous cells. No difference in the level of rRNA transcription was found between wild-type and rmm3 strains. However, rmm3 rDNA replicating intermediates exhibited an enhanced pause in the region of the replication origin, roughly 750 bp upstream from the rmm3 mutation. In footprinting of isolated nuclei, the rmm3 rDNA lacked the wild-type dimethyl sulfate (DMS) footprint in the promoter region adjacent to the base change. In addition, a DMS footprint in the origin region was lost in the rmm3 rDNA minichromosome. This is the first reported correlation in this system between an rDNA minichromosome maintenance defect and an altered footprint in the origin region. Our results suggest that a promoter region mutation can affect replication without detectably affecting transcription. We propose a model in which interactions between promoter and origin region complexes facilitate replication and maintenance of the Tetrahymena rDNA minichromosome. PMID:9566921
Khan, Abid; Giri, Sumanprava; Wang, Yating; Chakraborty, Arindam; Ghosh, Archit K.; Anantharaman, Aparna; Aggarwal, Vasudha; Sathyan, Kizhakke M.; Ha, Taekjip; Prasanth, Kannanganattu V.; Prasanth, Supriya G.
Ribosome biogenesis dictates the translational capacity of cells. Several mechanisms establish and maintain transcriptional output from eukaryotic ribosomal DNA (rDNA) loci. rDNA silencing is one such mechanism that ensures the inactivity and hence the maintenance of a silenced state of a subset of rRNA gene copies. Whereas oncogenic agents stimulate rRNA gene transcription, tumor suppressors decrease rRNA gene transcription. We demonstrate in mammalian cells that BANP, E5R, and Nac1 (BEN) domain 3 (BEND3), a quadruple BEN domain-containing protein, localizes in nucleoli and binds to ribosomal RNA gene promoters to help repress rRNA genes. Loss of BEND3 increases histone H3K4 trimethylation and, correspondingly, decreases rDNA promoter DNA methylation, consistent with a role for BEND3 in rDNA silencing. BEND3 associates with the nucleolar-remodeling complex (NoRC), and SUMOylated BEND3 stabilizes NoRC component TTF-1–interacting protein 5 via association with ubiquitin specific protease 21 (USP21) debiquitinase. Our results provide mechanistic insights into how the novel rDNA transcription repressor BEND3 acts together with NoRC to actively coordinate the establishment of rDNA silencing. PMID:26100909
Khan, Abid; Giri, Sumanprava; Wang, Yating; Chakraborty, Arindam; Ghosh, Archit K; Anantharaman, Aparna; Aggarwal, Vasudha; Sathyan, Kizhakke M; Ha, Taekjip; Prasanth, Kannanganattu V; Prasanth, Supriya G
Ribosome biogenesis dictates the translational capacity of cells. Several mechanisms establish and maintain transcriptional output from eukaryotic ribosomal DNA (rDNA) loci. rDNA silencing is one such mechanism that ensures the inactivity and hence the maintenance of a silenced state of a subset of rRNA gene copies. Whereas oncogenic agents stimulate rRNA gene transcription, tumor suppressors decrease rRNA gene transcription. We demonstrate in mammalian cells that BANP, E5R, and Nac1 (BEN) domain 3 (BEND3), a quadruple BEN domain-containing protein, localizes in nucleoli and binds to ribosomal RNA gene promoters to help repress rRNA genes. Loss of BEND3 increases histone H3K4 trimethylation and, correspondingly, decreases rDNA promoter DNA methylation, consistent with a role for BEND3 in rDNA silencing. BEND3 associates with the nucleolar-remodeling complex (NoRC), and SUMOylated BEND3 stabilizes NoRC component TTF-1-interacting protein 5 via association with ubiquitin specific protease 21 (USP21) debiquitinase. Our results provide mechanistic insights into how the novel rDNA transcription repressor BEND3 acts together with NoRC to actively coordinate the establishment of rDNA silencing.
Belenguer, P; Baldin, V; Mathieu, C; Prats, H; Bensaid, M; Bouche, G; Amalric, F
Transcription of ribosomal RNA genes is generally accepted to correlate with cell growth. Using primary cultures of adult bovine aortic endothelial (ABAE) cells, we have shown that transcription of rDNA in confluent cells falls to 5% of the transcription level in growing cells. Protein kinase NII appears to be a limiting factor to promote rDNA transcription in isolated nuclei of confluent cells. Protein kinase NII was detected by immunocytochemistry in the cytoplasm, nuclei and nucleoli of growing cells while it was no longer present in nucleoli of confluent cells. The kinase activity, in isolated nuclei, was estimated by endogenous phosphorylation of a specific substrate, nucleolin. A 10% residual activity was present in confluent cell nuclei compared to growing cell nuclei. Concomitantly, the transcription 'in vitro' of rDNA in the corresponding nuclei was also highly reduced (by 85%). Addition of exogenous protein kinase NII to confluent cell nuclei induced a strong increase in the phosphorylation of specific proteins including nucleolin. In parallel, the transcription of rDNA was increased by a factor of 5, to nearly the level observed in nuclei prepared from growing cells. These data suggest that, in confluent cells, factors necessary for rDNA transcription machinery are present but inactive in the nucleolus and that the phosphorylation of one or several of these factors (nucleolin, topoisomerase I,...) by protein kinase NII is a key event in the regulation of rDNA transcription. Images PMID:2780290
Alper, Iraz; Frenette, Michel; Labrie, Steve
The dimorphic yeast Geotrichum candidum (teleomorph: Galactomyces candidus) is commonly used to inoculate washed-rind and bloomy-rind cheeses. However, little is known about the phylogenetic lineage of this microorganism. We have sequenced the complete 18S, 5.8S, 26S ribosomal RNA genes and their internal transcribed spacers (ITS1) and ITS2 regions (5126 nucleotides) from 18 G. candidum strains from various environmental niches, with a focus on dairy strains. Multiple sequence alignments revealed the presence of 60 polymorphic sites, which is generally unusual for ribosomal DNA (rDNA) within a given species because of the concerted evolution mechanism. This mechanism drives genetic homogenization to prevent the divergent evolution of rDNA copies within individuals. While the polymorphisms observed were mainly substitutions, one insertion/deletion (indel) polymorphism was detected in ITS1. No polymorphic sites were detected downstream from this indel site, that is, in 5.8S and ITS2. More surprisingly, many sequence electrophoregrams generated during the sequencing of the rDNA had dual peaks, suggesting that many individuals exhibited intragenomic rDNA variability. The ITS1-5.8S-ITS2 regions of four strains were cloned. The sequence analysis of 68 clones revealed 32 different ITS1-5.8S-ITS2 variants within these four strains. Depending on the strain, from four to twelve variants were detected, indicating that multiple rDNA copies were present in the genomes of these G. candidum strains. These results contribute to the debate concerning the use of the ITS region for barcoding fungi and suggest that community profiling techniques based on rDNA should be used with caution.
Hartmann, S; Nason, J D; Bhattacharya, D
Sequence analysis of the hypervariable internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) is commonly used to gain insights into plant and animal population structure and phylogeny. We characterized ITS1, ITS2, and the 5.8S coding region of 18 senita (Lophocereus) individuals from 12 different populations in Baja as well as from closely related cactus species. Analyses of multiple clones demonstrated extensive paralogy in the senita rDNA gene family. We identified at least two putatively non-recombining rDNA operons in senita as well as multiple paralogous sequences within each operon. Usage of PCR, reverse transcriptase (RT)-PCR, Southern blot, primary sequence analyses of the 18S rDNA gene, and secondary structure analyses of the 5.8S rRNA showed that one of the operons encodes rDNA pseudogenes in a low copy-number (Truncated), whereas the second operon encodes an expressed rRNA (Functional). Surprisingly, we found extensive paralogy not only in the ITS regions but also in the 5.8S coding regions in senita both within and between operons. Phylogenetic analyses suggest that the second rDNA operon originated prior to the divergence of Lophocereus. A significant (p < 0.05) divergence-rate acceleration was found in the Lophocereus 5.8S rDNA coding region in the Functional operon in comparison to Pereskiopsis porteri (Cactaceae) and Portulaca molokiniensis (Portulacaceae) with Silene dioica and Spinacia oleracea as the outgroups.
Bueno, Danilo; Palacios-Gimenez, Octavio Manuel; Martí, Dardo Andrea; Mariguela, Tatiane Casagrande; Cabral-de-Mello, Diogo Cavalcanti
The 5S ribosomal DNA (rDNA) sequences are subject of dynamic evolution at chromosomal and molecular levels, evolving through concerted and/or birth-and-death fashion. Among grasshoppers, the chromosomal location for this sequence was established for some species, but little molecular information was obtained to infer evolutionary patterns. Here, we integrated data from chromosomal and nucleotide sequence analysis for 5S rDNA in two Abracris species aiming to identify evolutionary dynamics. For both species, two arrays were identified, a larger sequence (named type-I) that consisted of the entire 5S rDNA gene plus NTS (non-transcribed spacer) and a smaller (named type-II) with truncated 5S rDNA gene plus short NTS that was considered a pseudogene. For type-I sequences, the gene corresponding region contained the internal control region and poly-T motif and the NTS presented partial transposable elements. Between the species, nucleotide differences for type-I were noticed, while type-II was identical, suggesting pseudogenization in a common ancestor. At chromosomal point to view, the type-II was placed in one bivalent, while type-I occurred in multiple copies in distinct chromosomes. In Abracris, the evolution of 5S rDNA was apparently influenced by the chromosomal distribution of clusters (single or multiple location), resulting in a mixed mechanism integrating concerted and birth-and-death evolution depending on the unit.
Chand Dakal, Tikam; Giudici, Paolo; Solieri, Lisa
Arrays of repetitive ribosomal DNA (rDNA) sequences are generally expected to evolve as a coherent family, where repeats within such a family are more similar to each other than to orthologs in related species. The continuous homogenization of repeats within individual genomes is a recombination process termed concerted evolution. Here, we investigated the extent and the direction of concerted evolution in 43 yeast strains of the Zygosaccharomyces rouxii species complex (Z. rouxii, Z. sapae, Z. mellis), by analyzing two portions of the 35S rDNA cistron, namely the D1/D2 domains at the 5’ end of the 26S rRNA gene and the segment including the internal transcribed spacers (ITS) 1 and 2 (ITS regions). We demonstrate that intra-genomic rDNA sequence variation is unusually frequent in this clade and that rDNA arrays in single genomes consist of an intermixing of Z. rouxii, Z. sapae and Z. mellis-like sequences, putatively evolved by reticulate evolutionary events that involved repeated hybridization between lineages. The levels and distribution of sequence polymorphisms vary across rDNA repeats in different individuals, reflecting four patterns of rDNA evolution: I) rDNA repeats that are homogeneous within a genome but are chimeras derived from two parental lineages via recombination: Z. rouxii in the ITS region and Z. sapae in the D1/D2 region; II) intra-genomic rDNA repeats that retain polymorphisms only in ITS regions; III) rDNA repeats that vary only in their D1/D2 domains; IV) heterogeneous rDNA arrays that have both polymorphic ITS and D1/D2 regions. We argue that an ongoing process of homogenization following allodiplodization or incomplete lineage sorting gave rise to divergent evolutionary trajectories in different strains, depending upon temporal, structural and functional constraints. We discuss the consequences of these findings for Zygosaccharomyces species delineation and, more in general, for yeast barcoding. PMID:27501051
Cesarini, Elisa; D'Alfonso, Anna; Camilloni, Giorgio
Transcription-associated recombination is an important process involved in several aspects of cell physiology. In the ribosomal DNA (rDNA) of Saccharomyces cerevisiae, RNA polymerase II transcription-dependent recombination has been demonstrated among the repeated units. In this study, we investigate the mechanisms controlling this process at the chromatin level. On the basis of a small biased screening, we found that mutants of histone deacetylases and chromatin architectural proteins alter both the amount of Pol II-dependent noncoding transcripts and recombination products at rDNA in a coordinated manner. Of interest, chromatin immunoprecipitation analyses in these mutants revealed a corresponding variation of the histone H4 acetylation along the rDNA repeat, particularly at Lys-16. Here we provide evidence that a single, rapid, and reversible posttranslational modification-the acetylation of the H4K16 residue-is involved in the coordination of transcription and recombination at rDNA.
Gibbons, John G.; Branco, Alan T.; Godinho, Susana A.; Yu, Shoukai; Lemos, Bernardo
Tandemly repeated ribosomal DNA (rDNA) arrays are among the most evolutionary dynamic loci of eukaryotic genomes. The loci code for essential cellular components, yet exhibit extensive copy number (CN) variation within and between species. CN might be partly determined by the requirement of dosage balance between the 5S and 45S rDNA arrays. The arrays are nonhomologous, physically unlinked in mammals, and encode functionally interdependent RNA components of the ribosome. Here we show that the 5S and 45S rDNA arrays exhibit concerted CN variation (cCNV). Despite 5S and 45S rDNA elements residing on different chromosomes and lacking sequence similarity, cCNV between these loci is strong, evolutionarily conserved in humans and mice, and manifested across individual genotypes in natural populations and pedigrees. Finally, we observe that bisphenol A induces rapid and parallel modulation of 5S and 45S rDNA CN. Our observations reveal a novel mode of genome variation, indicate that natural selection contributed to the evolution and conservation of cCNV, and support the hypothesis that 5S CN is partly determined by the requirement of dosage balance with the 45S rDNA array. We suggest that human disease variation might be traced to disrupted rDNA dosage balance in the genome. PMID:25583482
Noleto, Rafael Bueno; Vicari, Marcelo Ricardo; Cipriano, Roger Raupp; Artoni, Roberto Ferreira; Cestari, Marta Margarete
Chromosomal features, location and variation of the major and minor rDNA genes cluster were studied in three pufferfish species: Sphoeroides greeleyi and Sphoeroides testudineus (Tetraodontidae) and Cyclichthys spinosus (Diodontidae). The location of the major rDNA was revealed with an 18S probe in two loci for all species. The minor rDNA loci (5S rDNA) was found in one chromosome pair in tetraodontid fishes and four sites located on two distinct chromosomal pairs in C. spinosus. A syntenical organization was not observed among the ribosomal genes. Signal homogeneity for GC/AT-DNA specific fluorochromes was observed in diodontid fish except in the NORs regions, which were CMA3-positive. Giemsa karyotypes of tetraodontid species presents 2n=46, having the same diploid value of other Sphoeroides species that have been investigated. On the other hand, the karyotype of C. spinosus, described for the first time, shows 2n=50 chromosomes (4m+18sm+12st+16a). The foreknowledge of the karyotypic structure of this group and also the physical mapping of certain genes could be very helpful for further DNA sequence analysis.
Jang, Tae-Soo; McCann, Jamie; Parker, John S.; Takayama, Koji; Hong, Suk-Pyo; Schneeweiss, Gerald M.
Glechoma L. (Lamiaceae) is distributed in eastern Asia and Europe. Understanding chromosome evolution in Glechoma has been strongly hampered by its small chromosomes, constant karyotype and polyploidy. Here phylogenetic patterns and chromosomal variation in Glechoma species are considered, using genome sizes, chromosome mapping of 5S and 35S rDNAs by fluorescence in situ hybridisation (FISH), and phylogenetic analyses of internal transcribed spacers (nrITS) of 35S rDNA and 5S rDNA NTS sequences. Species and populations of Glechoma are tetraploid (2n = 36) with base chromosome number of x = 9. Four chromosomes carry pericentric 5S rDNA sites in their short arms in all the species. Two to four of these chromosomes also carry 35S rDNA in subterminal regions of the same arms. Two to four other chromosomes have 35S rDNA sites, all located subterminally within short arms; one individual possessed additional weak pericentric 35S rDNA signals on three other chromosomes. Five types of rDNA locus distribution have been defined on the basis of 35S rDNA variation, but none is species-specific, and most species have more than one type. Glechoma hederacea has four types. Genome size in Glechoma ranges from 0.80 to 0.94 pg (1C), with low levels of intrapopulational variation in all species. Phylogenetic analyses of ITS and NTS sequences distinguish three main clades coinciding with geographical distribution: European (G. hederacea–G. hirsuta), Chinese and Korean (G. longituba), and Japanese (G. grandis). The paper presents the first comparative cytogenetic analyses of Glechoma species including karyotype structure, rDNA location and number, and genome size interpreted in a phylogenetic context. The observed variation suggests that the genus is still in genomic flux. Genome size, but not rDNA loci number and distribution, provides a character for species delimitation which allows better inferences of interspecific relationships to be made, in the absence of well
The original description of Henneguya adiposa, a myxozoan parasitizing channel catfish Ictalurus punctatus, is supplemented with new data on spore morphology, including photomicrographs and line drawings, as well as 18S small-subunit (SSU) ribosomal DNA (rDNA) sequence. Elongate, translucent, linear...
Robicheau, Brent M.; Susko, Edward; Harrigan, Amye M.
Approximately 35% of the human genome can be identified as sequence devoid of a selected-effect function, and not derived from transposable elements or repeated sequences. We provide evidence supporting a known origin for a fraction of this sequence. We show that: 1) highly degraded, but near full length, ribosomal DNA (rDNA) units, including both 45S and Intergenic Spacer (IGS), can be found at multiple sites in the human genome on chromosomes without rDNA arrays, 2) that these rDNA sequences have a propensity for being centromere proximal, and 3) that sequence at all human functional rDNA array ends is divergent from canonical rDNA to the point that it is pseudogenic. We also show that small sequence strings of rDNA (from 45S + IGS) can be found distributed throughout the genome and are identifiable as an “rDNA-like signal”, representing 0.26% of the q-arm of HSA21 and ∼2% of the total sequence of other regions tested. The size of sequence strings found in the rDNA-like signal intergrade into the size of sequence strings that make up the full-length degrading rDNA units found scattered throughout the genome. We conclude that the displaced and degrading rDNA sequences are likely of a similar origin but represent different stages in their evolution towards random sequence. Collectively, our data suggests that over vast evolutionary time, rDNA arrays contribute to the production of junk DNA. The concept that the production of rDNA pseudogenes is a by-product of concerted evolution represents a previously under-appreciated process; we demonstrate here its importance. PMID:28204512
Vance, V B; Thompson, E A; Bowman, L H
Truncated mouse ribosomal DNA (rDNA) genes were stably incorporated into rat HTC-5 cells by DNA-mediated cell transfection techniques. The mouse rDNA genes were accurately transcribed in these rat cells indicating that there is no absolute species specificity of rDNA transcription between mouse and rat. No more than 170 nucleotides of the 5' nontranscribed spacer was required for the accurate initiation of mouse rDNA transcription in rat cells. Further, the mouse transcripts were accurately cleaved at the 5' end of the 18S rRNA sequence, even though these transcripts contained neither the 3' end of mouse 18S rRNA nor any other downstream mouse sequences. Thus, cleavage at the 5' end of 18S rRNA is not dependent on long range interactions involving these downstream sequences. Images PMID:2997749
Briscoe, A; Tomkiel, J E
In Drosophila melanogaster, the rDNA loci function in ribosome biogenesis and nucleolar formation and also as sex chromosome pairing sites in male meiosis. These activities are not dependent on the heterochromatic location of the rDNA, because euchromatic transgenes are competent to form nucleoli and restore pairing to rDNA-deficient X chromosomes. These transgene studies, however, do not address requirements for the function of the endogenous rDNA loci within the heterochromatin. Here we describe two chromosome rearrangements that disrupt rDNA functions. Both rearrangements are translocations that cause an extreme bobbed visible phenotype and XY nondisjunction and meiotic drive in males. However, neither rearrangement interacts with a specific Y chromosome, Ymal(+), that induces male sterility in combination with rDNA deletions. Molecular studies show that the translocations are not associated with gross rearrangements of the rDNA repeat arrays. Rather, suppression of the bobbed phenotypes by Y heterochromatin suggests that decreased rDNA function is caused by a chromosomal position effect. While both translocations affect rDNA transcription, only one disrupts meiotic XY pairing, indicating that there are different cis-acting requirements for rDNA transcription and rDNA-mediated meiotic pairing. PMID:10880481
Holland, Michelle L; Lowe, Robert; Caton, Paul W; Gemma, Carolina; Carbajosa, Guillermo; Danson, Amy F; Carpenter, Asha A M; Loche, Elena; Ozanne, Susan E; Rakyan, Vardhman K
A suboptimal early-life environment, due to poor nutrition or stress during pregnancy, can influence lifelong phenotypes in the progeny. Epigenetic factors are thought to be key mediators of these effects. We show that protein restriction in mice from conception until weaning induces a linear correlation between growth restriction and DNA methylation at ribosomal DNA (rDNA). This epigenetic response remains into adulthood and is restricted to rDNA copies associated with a specific genetic variant within the promoter. Related effects are also found in models of maternal high-fat or obesogenic diets. Our work identifies environmentally induced epigenetic dynamics that are dependent on underlying genetic variation and establishes rDNA as a genomic target of nutritional insults.
Zhang, Qianqian; Agatha, Sabine; Zhang, Wuchang; Dong, Jun; Yu, Ying; Jiao, Nianzhi; Gong, Jun
To improve understanding of diversity, phylogeny and evolution in tintinnid ciliates, it is essential to link multiple molecular markers with properly identified and documented morphospecies. Accordingly, 54 tintinnid morphospecies/isolates mainly from the Yellow and East China Seas were collected and analysed. Using single-cell approaches, sequences were obtained for three rDNA loci (18S, ITS1-5.8S-ITS2, D1-D5 region of 28S). Twenty-six tintinnid morphospecies (29 isolates) are documented by micrographs, measurements, morphologically described, and compared with the original species description. Three rDNA loci-based phylogenetic analyses were then performed for these identified isolates. Sequences from 25 unidentified species/isolates were also included in the comparison of the three rDNA loci. Ribosomal DNA genes of the genus Leprotintinnus were analysed for the first time, showing that Leprotintinnus was closely related to Tintinnopsis radix and branched distinctly apart from the family Tintinnidiidae. Four novel clades (VI to IX) of the Tintinnopsis complex emerged in the 18S genealogies. Analyses of the relative variability in the ITS and 28S regions vs. the 18S rDNA showed that the ITS1-5.8S-ITS2 and ITS2 regions well co-varied with the 18S rDNA when the variations of the latter were less than 3%, whereas at difference of less than 1%, no correlation was found between the compared loci. These findings highlight the difficulties in using variable locus-based cut-off divergences in circumscribing tintinnid morphospecies.
Al-Banna, L; Williamson, V; Gardner, S L
We used nucleotide sequences of the large subunit ribosomal genes (26S rDNA) to examine evolutionary relationships among species of the genus Pratylenchus (Order: Tylenchida, Family: Pratylenchidae), commonly known as root-lesion nematodes. Ten species of Pratylenchus were studied including, P. penetrans, P. crenatus, P. minyus, P. vulnus, P. thornei, P. musicola, P. coffeae, P. hexincisus, P. scribneri, and P. brachyurus. The species Hirschmanniella belli, Meloidogyne javanica, Heterorhabditis bacteriophora, Nacobbus aberrans, Radopholus similis, and Xiphinema index were used as outgroups. Based on parsimony analyses of approximately 307 aligned nucleotides of the D3 expansion region of the 26S rDNA, it is clear that species of Pratylenchus are a paraphyletic assemblage. The outgroup taxon H. belli shares a common ancestor with the clade that includes P. vulnus and P. crenatus while N. aberrans and R. similis share a common ancestor with 5 other species included in this study.
Zhao, Ya-E; Xu, Ji-Ru; Hu, Li; Wu, Li-Ping; Wang, Zheng-Hang
The study for the first time attempted to accomplish 18S ribosomal DNA (rDNA) complete sequence amplification and analysis for three Demodex species (Demodex folliculorum, Demodex brevis and Demodex canis) based on gDNA extraction from individual mites. The mites were treated by DNA Release Additive and Hot Start II DNA Polymerase so as to promote mite disruption and increase PCR specificity. Determination of D. folliculorum gDNA showed that the gDNA yield reached the highest at 1 mite, tending to descend with the increase of mite number. The individual mite gDNA was successfully used for 18S rDNA fragment (about 900 bp) amplification examination. The alignments of 18S rDNA complete sequences of individual mite samples and those of pooled mite samples ( ≥ 1000mites/sample) showed over 97% identities for each species, indicating that the gDNA extracted from a single individual mite was as satisfactory as that from pooled mites for PCR amplification. Further pairwise sequence analyses showed that average divergence, genetic distance, transition/transversion or phylogenetic tree could not effectively identify the three Demodex species, largely due to the differentiation in the D. canis isolates. It can be concluded that the individual Demodex mite gDNA can satisfy the molecular study of Demodex. 18S rDNA complete sequence is suitable for interfamily identification in Cheyletoidea, but whether it is suitable for intrafamily identification cannot be confirmed until the ascertainment of the types of Demodex mites parasitizing in dogs.
Pérez-García, Concepción; Hurtado, Ninoska S.; Morán, Paloma; Pasantes, Juan J.
The chromosomal changes accompanying bivalve evolution are an area about which few reports have been published. To improve our understanding on chromosome evolution in Veneridae, ribosomal RNA gene clusters were mapped by fluorescent in situ hybridization (FISH) to chromosomes of five species of venerid clams (Venerupis corrugata, Ruditapes philippinarum, Ruditapes decussatus, Dosinia exoleta, and Venus verrucosa). The results were anchored to the most comprehensive molecular phylogenetic tree currently available for Veneridae. While a single major rDNA cluster was found in each of the five species, the number of 5S rDNA clusters showed high interspecies variation. Major rDNA was either subterminal to the short arms or intercalary to the long arms of metacentric or submetacentric chromosomes, whereas minor rDNA signals showed higher variability. Major and minor rDNAs map to different chromosome pairs in all species, but in R. decussatus one of the minor rDNA gene clusters and the major rDNA cluster were located in the same position on a single chromosome pair. This interspersion of both sequences was confirmed by fiber FISH. Telomeric signals appeared at both ends of every chromosome in all species. FISH mapping data are discussed in relation to the molecular phylogenetic trees currently available for Veneridae. PMID:24967400
Kang, Jian; Kusnadi, Eric P.; Ogden, Allison J.; Hicks, Rodney J.; Bammert, Lukas; Kutay, Ulrike; Hung, Sandy; Sanij, Elaine; Hannan, Ross D.; Hannan, Katherine M.; Pearson, Richard B.
Dysregulation of RNA polymerase I (Pol I)-dependent ribosomal DNA (rDNA) transcription is a consistent feature of malignant transformation that can be targeted to treat cancer. Understanding how rDNA transcription is coupled to the availability of growth factors and nutrients will provide insight into how ribosome biogenesis is maintained in a tumour environment characterised by limiting nutrients. We demonstrate that modulation of rDNA transcription initiation, elongation and rRNA processing is an immediate, co-regulated response to altered amino acid abundance, dependent on both mTORC1 activation of S6K1 and MYC activity. Growth factors regulate rDNA transcription initiation while amino acids modulate growth factor-dependent rDNA transcription by primarily regulating S6K1-dependent rDNA transcription elongation and processing. Thus, we show for the first time amino acids regulate rRNA synthesis by a distinct, post-initiation mechanism, providing a novel model for integrated control of ribosome biogenesis that has implications for understanding how this process is dysregulated in cancer. PMID:27385002
Xu, Yinfeng; Wan, Wei; Shou, Xin; Huang, Rui; You, Zhiyuan; Shou, Yanhong; Wang, Lingling; Zhou, Tianhua; Liu, Wei
Cells control their metabolism through modulating the anabolic and catabolic pathways. TP53INP2/DOR (tumor protein p53 inducible nuclear protein 2), participates in cell catabolism by serving as a promoter of autophagy. Here we uncover a novel function of TP53INP2 in protein synthesis, a major biosynthetic and energy-consuming anabolic process. TP53INP2 localizes to the nucleolus through its nucleolar localization signal (NoLS) located at the C-terminal domain. Chromatin immunoprecipitation (ChIP) assays detected an association of TP53INP2 with the ribosomal DNA (rDNA), when exclusion of TP53INP2 from the nucleolus repressed rDNA promoter activity and the production of ribosomal RNA (rRNA) and proteins. The removal of TP53INP2 also impaired the association of the POLR1/RNA polymerase I preinitiation complex (PIC) with rDNA. Further, TP53INP2 interacts directly with POLR1 PIC, and is required for the assembly of the complex. These data indicate that TP53INP2 promotes ribosome biogenesis through facilitating rRNA synthesis at the nucleolus, suggesting a dual role of TP53INP2 in cell metabolism, assisting anabolism on the nucleolus, and stimulating catabolism off the nucleolus.
Maggert, Keith A
The ribosomal DNA (rDNA) arrays are causal agents in X-Y chromosome pairing in meiosis I of Drosophila males. Despite broad variation in X-linked and Y-linked rDNA copy number, polymorphisms in regulatory/spacer sequences between rRNA genes, and variance in copy number of interrupting R1 and R2 retrotransposable elements, there is little evidence that different rDNA arrays affect pairing efficacy. I investigated whether induced rDNA copy number polymorphisms affect chromosome pairing in a "competitive" situation in which complex pairing configurations were possible using males with XYY constitution. Using a common normal X chromosome, one of two different full-length Y chromosomes, and a third chromosome from a series of otherwise-isogenic rDNA deletions, I detected no differences in X-Y or Y-Y pairing or chromosome segregation frequencies that could not be attributed to random variation alone. This work was performed in the context of an undergraduate teaching program at Texas A&M University, and I discuss the pedagogical utility of this and other such experiments.
Maggert, Keith A.
The ribosomal DNA (rDNA) arrays are causal agents in X-Y chromosome pairing in meiosis I of Drosophila males. Despite broad variation in X-linked and Y-linked rDNA copy number, polymorphisms in regulatory/spacer sequences between rRNA genes, and variance in copy number of interrupting R1 and R2 retrotransposable elements, there is little evidence that different rDNA arrays affect pairing efficacy. I investigated whether induced rDNA copy number polymorphisms affect chromosome pairing in a “competitive” situation in which complex pairing configurations were possible using males with XYY constitution. Using a common normal X chromosome, one of two different full-length Y chromosomes, and a third chromosome from a series of otherwise-isogenic rDNA deletions, I detected no differences in X-Y or Y-Y pairing or chromosome segregation frequencies that could not be attributed to random variation alone. This work was performed in the context of an undergraduate teaching program at Texas A&M University, and I discuss the pedagogical utility of this and other such experiments. PMID:24449686
Warsen, Adelaide E; Krug, Melissa J; LaFrentz, Stacey; Stanek, Danielle R; Loge, Frank J; Call, Douglas R
We developed a DNA microarray suitable for simultaneous detection and discrimination between multiple bacterial species based on 16S ribosomal DNA (rDNA) polymorphisms using glass slides. Microarray probes (22- to 31-mer oligonucleotides) were spotted onto Teflon-masked, epoxy-silane-derivatized glass slides using a robotic arrayer. PCR products (ca. 199 bp) were generated using biotinylated, universal primer sequences, and these products were hybridized overnight (55 degrees C) to the microarray. Targets that annealed to microarray probes were detected using a combination of Tyramide Signal Amplification and Alexa Fluor 546. This methodology permitted 100% specificity for detection of 18 microbes, 15 of which were fish pathogens. With universal 16S rDNA PCR (limited to 28 cycles), detection sensitivity for purified control DNA was equivalent to <150 genomes (675 fg), and this sensitivity was not adversely impacted either by the presence of competing bacterial DNA (1.1 x 10(6) genomes; 5 ng) or by the addition of up to 500 ng of fish DNA. Consequently, coupling 16S rDNA PCR with a microarray detector appears suitable for diagnostic detection and surveillance for commercially important fish pathogens.
Assuming systematic exchanges between nucleotides (swinger RNAs) resolves genomic 'parenthood' of some orphan mitochondrial transcripts. Twenty-three different systematic nucleotide exchanges (bijective transformations) exist. Similarities between transcription and replication suggest occurrence of swinger DNA. GenBank searches for swinger DNA matching the 23 swinger versions of human and mouse mitogenomes detect only vertebrate mitochondrial swinger DNA for swinger type AT+CG (from five different studies, 149 sequences) matching three human and mouse mitochondrial genes: 12S and 16S ribosomal RNAs, and cytochrome oxidase subunit I. Exchange A<->T+C<->G conserves self-hybridization properties, putatively explaining swinger biases for rDNA, against protein coding genes. Twenty percent of the regular human mitochondrial 16S rDNA consists of short swinger repeats (from 13 exchanges). Swinger repeats could originate from recombinations between regular and swinger DNA: duplicated mitochondrial genes of the parthenogenetic gecko Heteronotia binoei include fewer short A<->T+C<->G swinger repeats than non-duplicated mitochondrial genomes of that species. Presumably, rare recombinations between female and male mitochondrial genes (and in parthenogenetic situations between duplicated genes), favors reverse-mutations of swinger repeat insertions, probably because most inserts affect negatively ribosomal function. Results show that swinger DNA exists, and indicate that swinger polymerization contributes to the genesis of genetic material and polymorphism.
Vierna, J; Wehner, S; Höner zu Siederdissen, C; Martínez-Lage, A; Marz, M
Several studies on 5S ribosomal DNA (5S rDNA) have been focused on a subset of the following features in mostly one organism: number of copies, pseudogenes, secondary structure, promoter and terminator characteristics, genomic arrangements, types of non-transcribed spacers and evolution. In this work, we systematically analyzed 5S rDNA sequence diversity in available metazoan genomes, and showed organism-specific and evolutionary-conserved features. Putatively functional sequences (12 766) from 97 organisms allowed us to identify general features of this multigene family in animals. Interestingly, we show that each mammal species has a highly conserved (housekeeping) 5S rRNA type and many variable ones. The genomic organization of 5S rDNA is still under debate. Here, we report the occurrence of several paralog 5S rRNA sequences in 58 of the examined species, and a flexible genome organization of 5S rDNA in animals. We found heterogeneous 5S rDNA clusters in several species, supporting the hypothesis of an exchange of 5S rDNA from one locus to another. A rather high degree of variation of upstream, internal and downstream putative regulatory regions appears to characterize metazoan 5S rDNA. We systematically studied the internal promoters and described three different types of termination signals, as well as variable distances between the coding region and the typical termination signal. Finally, we present a statistical method for detection of linkage among noncoding RNA (ncRNA) gene families. This method showed no evolutionary-conserved linkage among 5S rDNAs and any other ncRNA genes within Metazoa, even though we found 5S rDNA to be linked to various ncRNAs in several clades. PMID:23838690
rRNA genes consist of long tandem repeats clustered on chromosomes, and their products are important functional components of the ribosome. In common wheat (Triticum aestivum), rDNA loci from the A and D genomes were largely lost during the evolutionary process. This biased DNA elimination may be related to asymmetric transcription and epigenetic modifications caused by the polyploid formation. Here, we observed both sets of parental nucleolus organizing regions (NORs) were expressed after hybridization, but asymmetric silencing of one parental NOR was immediately induced by chromosome doubling, and reversing the ploidy status could not reactivate silenced NORs. Furthermore, increased CHG and CHH DNA methylation on promoters was accompanied by asymmetric silencing of NORs. Enrichment of H3K27me3 and H3K9me2 modifications was also observed to be a direct response to increased DNA methylation and transcriptional inactivation of NOR loci. Both A and D genome NOR loci with these modifications started to disappear in the S4 generation and were completely eliminated by the S7 generation in synthetic tetraploid wheat. Our results indicated that asymmetric epigenetic modification and elimination of rDNA sequences between different donor genomes may lead to stable allopolyploid wheat with increased differentiation and diversity. PMID:25415973
Angeletti, Silvia; Lorino, Giulia; Gherardi, Giovanni; Battistoni, Fabrizio; De Cesaris, Marina; Dicuonzo, Giordano
For 279 clinically isolated specimens identified by commercial kits as enterococci, genotypic identification was performed by two multiplex PCRs, one with ddlE. faecalis and ddlE. faecium primers and another with vanC-1 and vanC-2/3 primers, and by 16S ribosomal DNA (rDNA) sequencing. For 253 strains, phenotypic and genotypic results were the same. Multiplex PCR allowed for the identification of 13 discordant results. Six strains were not enterococci and were identified by 16S rDNA sequencing. For 5 discordant and 10 concordant enterococcal strains, 16S rDNA sequencing was needed. Because many supplementary tests are frequently necessary for phenotypic identification, the molecular approach is a good alternative. PMID:11158155
Vierna, J; Jensen, K T; Martínez-Lage, A; González-Tizón, A M
The linkage between 5S ribosomal DNA and other multigene families has been detected in many eukaryote lineages, but whether it provides any selective advantage remains unclear. In this work, we report the occurrence of linked units of 5S ribosomal DNA (5S rDNA) and U1 small nuclear DNA (U1 snDNA) in 10 razor shell species (Mollusca: Bivalvia: Pharidae) from four different genera. We obtained several clones containing partial or complete repeats of both multigene families in which both types of genes displayed the same orientation. We provide a comprehensive collection of razor shell 5S rDNA clones, both with linked and nonlinked organisation, and the first bivalve U1 snDNA sequences. We predicted the secondary structures and characterised the upstream and downstream conserved elements, including a region at -25 nucleotides from both 5S rDNA and U1 snDNA transcription start sites. The analysis of 5S rDNA showed that some nontranscribed spacers (NTSs) are more closely related to NTSs from other species (and genera) than to NTSs from the species they were retrieved from, suggesting birth-and-death evolution and ancestral polymorphism. Nucleotide conservation within the functional regions suggests the involvement of purifying selection, unequal crossing-overs and gene conversions. Taking into account this and other studies, we discuss the possible mechanisms by which both multigene families could have become linked in the Pharidae lineage. The reason why 5S rDNA is often found linked to other multigene families seems to be the result of stochastic processes within genomes in which its high copy number is determinant.
Ksiazczyk, T; Taciak, M; Zwierzykowski, Z
This study focuses on the variability of chromosomal location and number of ribosomal DNA (rDNA) sites in some diploid and autotetraploid Festuca pratensis and Lolium perenne cultivars, as well as on identification of rDNA-bearing chromosomes in their triploid and tetraploid F. pratensis × L. perenne hybrids. The rDNA loci were mapped using fluorescence in situ hybridization (FISH) with 5S and 25S rDNA probes, and the origin of parental genomes was verified by genomic in situ hybridization (GISH) with L. perenne genomic DNA as a probe, and F. pratensis genomic DNA as a block. FISH detected variation in the number and chromosomal location of both 5S and 45S rDNA sites. In F. pratensis mostly additional signals of 5S rDNA loci occurred, as compared with standard F. pratensis karyotypes. Losses of 45S rDNA loci were more frequent in L. perenne cultivars and intergeneric hybrids. Comparison of the F. pratensis and L. perenne genomes approved a higher number of rDNA sites as well as variation in chromosomal rDNA location in L. perenne. A greater instability of F. pratensis-genome-like and L. perenne-genome-like chromosomes in tetraploid hybrids was revealed, indicating gains and losses of rDNA loci, respectively. Our data indicate that the rDNA loci physically mapped on chromosomes 2 and 3 in F. pratensis and on chromosome 3 in L. perenne are useful markers for these chromosomes in intergeneric Festuca × Lolium hybrids.
Ironside, Joseph Edward
Microsporidian strains are usually classified on the basis of their ribosomal DNA (rDNA) sequences. Although rDNA occurs as multiple copies, in most non-microsporidian species copies within a genome occur as tandem arrays and are homogenised by concerted evolution. In contrast, microsporidian rDNA units are dispersed throughout the genome in some species, and on this basis are predicted to undergo reduced concerted evolution. Furthermore many microsporidian species appear to be asexual and should therefore exhibit reduced genetic diversity due to a lack of recombination. Here, DNA sequences are compared between microsporidia with different life cycles in order to determine the effects of concerted evolution and sexual reproduction upon the diversity of rDNA and protein coding genes. Comparisons of cloned rDNA sequences between microsporidia of the genus Nosema with different life cycles provide evidence of intragenomic variability coupled with strong purifying selection. This suggests a birth and death process of evolution. However, some concerted evolution is suggested by clustering of rDNA sequences within species. Variability of protein-coding sequences indicates that considerable intergenomic variation also occurs between microsporidian cells within a single host. Patterns of variation in microsporidian DNA sequences indicate that additional diversity is generated by intragenomic and/or intergenomic recombination between sequence variants. The discovery of intragenomic variability coupled with strong purifying selection in microsporidian rRNA sequences supports the hypothesis that concerted evolution is reduced when copies of a gene are dispersed rather than repeated tandemly. The presence of intragenomic variability also renders the use of rDNA sequences for barcoding microsporidia questionable. Evidence of recombination in the single-copy genes of putatively asexual microsporidia suggests that these species may undergo cryptic sexual reproduction, a
Ironside, Joseph Edward
Microsporidian strains are usually classified on the basis of their ribosomal DNA (rDNA) sequences. Although rDNA occurs as multiple copies, in most non-microsporidian species copies within a genome occur as tandem arrays and are homogenised by concerted evolution. In contrast, microsporidian rDNA units are dispersed throughout the genome in some species, and on this basis are predicted to undergo reduced concerted evolution. Furthermore many microsporidian species appear to be asexual and should therefore exhibit reduced genetic diversity due to a lack of recombination. Here, DNA sequences are compared between microsporidia with different life cycles in order to determine the effects of concerted evolution and sexual reproduction upon the diversity of rDNA and protein coding genes. Comparisons of cloned rDNA sequences between microsporidia of the genus Nosema with different life cycles provide evidence of intragenomic variability coupled with strong purifying selection. This suggests a birth and death process of evolution. However, some concerted evolution is suggested by clustering of rDNA sequences within species. Variability of protein-coding sequences indicates that considerable intergenomic variation also occurs between microsporidian cells within a single host. Patterns of variation in microsporidian DNA sequences indicate that additional diversity is generated by intragenomic and/or intergenomic recombination between sequence variants. The discovery of intragenomic variability coupled with strong purifying selection in microsporidian rRNA sequences supports the hypothesis that concerted evolution is reduced when copies of a gene are dispersed rather than repeated tandemly. The presence of intragenomic variability also renders the use of rDNA sequences for barcoding microsporidia questionable. Evidence of recombination in the single-copy genes of putatively asexual microsporidia suggests that these species may undergo cryptic sexual reproduction, a
Wisotzkey, J. D.; Jurtshuk, P. Jr; Fox, G. E.
The sequence of the major portion of a Bacillus cycloheptanicus strain SCH(T) 16S rRNA gene is reported. This sequence suggests that B. cycloheptanicus is genetically quite distinct from traditional Bacillus strains (e.g., B. subtilis) and may be properly regarded as belonging to a different genus. The sequence was determined from DNA that was produced by direct amplification of ribosomal DNA from a lyophilized cell pellet with straightforward polymerase chain reaction (PCR) procedures. By obviating the need to revive cell cultures from the lyophile pellet, this approach facilitates rapid 16S rDNA sequencing and thereby advances studies in molecular systematics.
Zagoskin, Maxim V.; Lazareva, Valentina I.; Grishanin, Andrey K.; Mukha, Dmitry V.
The utility of various regions of the ribosomal repeat unit for phylogenetic analysis was examined in 16 species representing four families, nine genera, and two orders of the subclass Copepoda (Crustacea). Fragments approximately 2000 bp in length containing the ribosomal DNA (rDNA) 18S and 28S gene fragments, the 5.8S gene, and the internal transcribed spacer regions I and II (ITS1 and ITS2) were amplified and analyzed. The DAMBE (Data Analysis in Molecular Biology and Evolution) software was used to analyze the saturation of nucleotide substitutions; this test revealed the suitability of both the 28S gene fragment and the ITS1/ITS2 rDNA regions for the reconstruction of phylogenetic trees. Distance (minimum evolution) and probabilistic (maximum likelihood, Bayesian) analyses of the data revealed that the 28S rDNA and the ITS1 and ITS2 regions are informative markers for inferring phylogenetic relationships among families of copepods and within the Cyclopidae family and associated genera. Split-graph analysis of concatenated ITS1/ITS2 rDNA regions of cyclopoid copepods suggested that the Mesocyclops, Thermocyclops, and Macrocyclops genera share complex evolutionary relationships. This study revealed that the ITS1 and ITS2 regions potentially represent different phylogenetic signals. PMID:25215300
Zagoskin, Maxim V; Lazareva, Valentina I; Grishanin, Andrey K; Mukha, Dmitry V
The utility of various regions of the ribosomal repeat unit for phylogenetic analysis was examined in 16 species representing four families, nine genera, and two orders of the subclass Copepoda (Crustacea). Fragments approximately 2000 bp in length containing the ribosomal DNA (rDNA) 18S and 28S gene fragments, the 5.8S gene, and the internal transcribed spacer regions I and II (ITS1 and ITS2) were amplified and analyzed. The DAMBE (Data Analysis in Molecular Biology and Evolution) software was used to analyze the saturation of nucleotide substitutions; this test revealed the suitability of both the 28S gene fragment and the ITS1/ITS2 rDNA regions for the reconstruction of phylogenetic trees. Distance (minimum evolution) and probabilistic (maximum likelihood, Bayesian) analyses of the data revealed that the 28S rDNA and the ITS1 and ITS2 regions are informative markers for inferring phylogenetic relationships among families of copepods and within the Cyclopidae family and associated genera. Split-graph analysis of concatenated ITS1/ITS2 rDNA regions of cyclopoid copepods suggested that the Mesocyclops, Thermocyclops, and Macrocyclops genera share complex evolutionary relationships. This study revealed that the ITS1 and ITS2 regions potentially represent different phylogenetic signals.
Sagastume, Soledad; del Aguila, Carmen; Martín-Hernández, Raquel; Higes, Mariano; Henriques-Gil, Nuno
Nosema ceranae is currently one of the major pathogens of honeybees, related to the worldwide colony losses phenomenon. The genotyping of strains based on ribosomal DNA (rDNA) can be misleading if the repeated units are not identical. The analysis of cloned rDNA fragments containing the intergenic spacer (IGS) and part of the rDNA small-subunit (SSU) gene, from N. ceranae isolates from different European and Central Asia populations, revealed a high diversity of sequences. The variability involved single-nucleotide polymorphisms and insertion/deletions, resulting in 79 different haplotypes. Two sequences from the same isolate could be as different as any pair of sequences from different samples; in contrast, identical haplotypes were also found in very different geographical origins. Consequently, haplotypes cannot be organized in a consistent phylogenetic tree, clearly indicating that rDNA is not a reliable marker for the differentiation of N. ceranae strains. The results indicate that recombination between different sequences may produce new variants, which is quite surprising in microsporidia, usually considered to have an asexual mode of reproduction. The diversity of sequences and their geographical distribution indicate that haplotypes of different lineages may occasionally be present in a same cell and undergo homologue recombination, therefore suggesting a sexual haplo-diploid cycle.
Lin, Q; Li, H M; Gao, M; Wang, X Y; Ren, W X; Cong, M M; Tan, X C; Chen, C X; Yu, S K; Zhao, G H
In the present study, a total of 20 nematode isolates, (including 10 male and 10 female worms) representing Baylisascaris schroederi from 5 Qinling subspecies of giant pandas (Ailuropoda melanoleuca) in Shaanxi Province of China, were characterized and grouped genetically by the first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA (rDNA). The rDNA fragment spanning 3' end of 18S rDNA, complete ITS-1 rDNA, and 5' end of 5.8S rDNA were amplified and sequenced. The sequence variability in ITS-1 rDNA was examined within B. schroederi and among parasites in order Ascaridata available in GenBank™, and their phylogenetic relationships were also reconstructed. The sequences of ITS-1 rDNA for all the B. schroederi isolates were 427 bp in length, with no genetic variation detected among these isolates. Phylogenetic analyses based on the ITS-1 rDNA sequences revealed that all the male and female B. schroederi isolates sequenced in the present study were posited into the clade of genus Baylisascaris, sistered to zoonotic nematodes in genus Ascaris, and the ITS-1 rDNA sequence could distinguish different species in order Ascaridata. These results showed that the ITS-1 rDNA provides a suitable molecular marker for the inter-species phylogenetic analysis and differential identification of nematodes in order Ascaridata.
Jetybayev, I E; Bugrov, A G; Karamysheva, T V; Camacho, J P M; Rubtsov, N B
Chromosome location of ribosomal DNA (rDNA) and telomeric repeats was analysed in mitotic chromosomes of 15 species of Gomphocerinae grasshoppers belonging to the tribes Arcypterini, Gomphocerini, Stenobothrini, and Chrysochraontini. Two types of rDNA distribution were found in the Gomphocerini tribe. Type 1, found in 9 species, was characterized by the presence of rDNA in the short arm of the long biarmed chromosomes 2 and 3 and, in some species, also in the X chromosome. Type 2 was found only in Aeropus sibiricus and Stauroderus scalaris and consisted in the presence of pericentromeric rDNA blocks in all chromosomes. A comparison of rDNA distribution in Gomphocerini species with 2n ♂ = 23, 2n ♂ = 21, and 2n ♂ = 17 suggested the possible involvement of chromosome 6 in the ancestral karyotype (2n ♂ = 23) in 1 of the 3 centric fusions that decreased the chromosome number in these species. In the tribe Stenobothrini, Stenobothrus eurasius carried a single rDNA cluster in the X chromosome, likewise 2 Spanish species previously analysed, but Omocestus viridulus unusually showed a single rDNA cluster in the longest autosome. Telomeric repeats were located primarily on the ends of chromosome arms. In 2 species, however, we observed the presence of interstitial clusters outside telomeric regions. The first one, Aeropus sibiricus, exhibited a polymorphic interstitial site of telomeric repeats in chromosome 6 as a consequence of a paracentric inversion. Most remarkably, Chorthippus jacobsoni showed the presence of telomeric repeats in the pericentric regions of the 3 biarmed chromosome pairs originated by centric fusion, thus suggesting that these rearrangements were not of the Robertsonian type but true centric fusion with a probable generation of dicentric chromosomes.
Rosato, Marcela; Moreno-Saiz, Juan C; Galián, José A; Rosselló, Josep A
Several genome duplications have been identified in the evolution of seed plants, providing unique systems for studying karyological processes promoting diversification and speciation. Knowledge about the number of ribosomal DNA (rDNA) loci, together with their chromosomal distribution and structure, provides clues about organismal and molecular evolution at various phylogenetic levels. In this work, we aim to elucidate the evolutionary dynamics of karyological and rDNA site-number variation in all known taxa of subtribe Vellinae, showing a complex scenario of ancestral and more recent polyploid events. Specifically, we aim to infer the ancestral chromosome numbers and patterns of chromosome number variation, assess patterns of variation of both 45S and 5S rDNA families, trends in site-number change of rDNA loci within homoploid and polyploid series, and reconstruct the evolutionary history of rDNA site number using a phylogenetic hypothesis as a framework. The best-fitting model of chromosome number evolution with a high likelihood score suggests that the Vellinae core showing x = 17 chromosomes arose by duplication events from a recent x = 8 ancestor. Our survey suggests more complex patterns of polyploid evolution than previously noted for Vellinae. High polyploidization events (6x, 8x) arose independently in the basal clade Vella castrilensis-V. lucentina, where extant diploid species are unknown. Reconstruction of ancestral rDNA states in Vellinae supports the inference that the ancestral number of loci in the subtribe was two for each multigene family, suggesting that an overall tendency towards a net loss of 5S rDNA loci occurred during the splitting of Vellinae ancestors from the remaining Brassiceae lineages. A contrasting pattern for rDNA site change in both paleopolyploid and neopolyploid species was linked to diversification of Vellinae lineages. This suggests dynamic and independent changes in rDNA site number during speciation processes and a
Castro, J; Sánchez, L; Martínez, P; Lucchini, S D; Nardi, I
Using restriction endonuclease mapping, we have analyzed the organization of rDNA (DNA coding for ribosomal RNA (rRNA)) units in the salmonid fish Salmo trutta, as an initial step toward understand the molecular basis of a nucleolar organizer region (NOR) site polymorphism detected in this species. The size of the rDNA units ranged between 15 and 23 kb, with remarkable variation both within individuals and between populations. Three regions of internal tandem repetitiveness responsible for this length polymorphism were located to the intergenic spacers. NOR site polymorphic individuals showed a higher number of length classes, in some cases forming a complete 1 kb fragment ladder. The amount of rRNA genes was as much as 8-fold higher in polymorphic individuals compared with standard individuals. All individuals from the most polymorphic population showed a 14-kb insertion of unknown nature in a small proportion (below 25%) of the 28S rRNA genes.
Kurtzman, C P; Robnett, C J
Clinically important species of Candida and related organisms were compared for extent of nucleotide divergence in the 5' end of the large-subunit (26S) ribosomal DNA (rDNA) gene. This rDNA region is sufficiently variable to allow reliable separation of all known clinically significant yeast species. Of the 204 described species examined, 21 appeared to be synonyms of previously described organisms. Phylogenetic relationships among the species are presented. PMID:9114410
Drosopoulou, Elena; Nakou, Ifigeneia; Síchová, Jindra; Kubíčková, Svatava; Marec, František; Mavragani-Tsipidou, Penelope
The olive fruit fly, Bactrocera oleae, has a diploid set of 2n = 12 chromosomes including a pair of sex chromosomes, XX in females and XY in males, but polytene nuclei show only five polytene chromosomes, obviously formed by five autosome pairs. Here we examined the fate of the sex chromosomes in the polytene complements of this species using fluorescence in situ hybridization (FISH) with the X and Y chromosome-derived probes, prepared by laser microdissection of the respective chromosomes from mitotic metaphases. Specificity of the probes was verified by FISH in preparations of mitotic chromosomes. In polytene nuclei, both probes hybridized strongly to a granular heterochromatic network, indicating thus underreplication of the sex chromosomes. The X chromosome probe (in both female and male nuclei) highlighted most of the granular mass, whereas the Y chromosome probe (in male nuclei) identified a small compact body of this heterochromatic network. Additional hybridization signals of the X probe were observed in the centromeric region of polytene chromosome II and in the telomeres of six polytene arms. We also examined distribution of the major ribosomal DNA (rDNA) using FISH with an 18S rDNA probe in both mitotic and polytene chromosome complements of B. oleae. In mitotic metaphases, the probe hybridized exclusively to the sex chromosomes. The probe signals localized a discrete rDNA site at the end of the short arm of the X chromosome, whereas they appeared dispersed over the entire dot-like Y chromosome. In polytene nuclei, the rDNA was found associated with the heterochromatic network representing the sex chromosomes. Only in nuclei with preserved nucleolar structure, the probe signals were scattered in the restricted area of the nucleolus. Thus, our study clearly shows that the granular heterochromatic network of polytene nuclei in B. oleae is formed by the underreplicated sex chromosomes and associated rDNA.
Colomba, M S; Vitturi, R; Zunino, M
In the present work the chromosome complement (2n = 18; 8AA + XY) of the stag beetle Dorcus parallelipipedus L. (Scarabaeoidea: Lucanidae) is analyzed using conventional Giemsa staining, banding techniques and ribosomal fluorescent in situ hybridization (rDNA FISH). rDNA FISH remains the unique tool for providing a clear-cut identification of Nucleolar Organizer Regions (NORs) when conventional banding methods such as silver- and CMA3-staining proved to be inadequate. The dull, homogeneous CMA3 fluorescence of all chromosomes indicates the absence of markedly GC rich compartmentalized regions in D. parallelipipedus genome. Silver impregnation inadequacy in detecting NOR regions is to be sought in the unusual extensive silver stainability of heterochromatic material which, on the contrary of what stated for vertebrates, seems to be a common feature in Scarabaeoidea species.
Lau, S K P; Ng, K H L; Woo, P C Y; Yip, K‐t; Fung, A M Y; Woo, G K S; Chan, K‐m; Que, T‐l
Using full 16S ribosomal RNA (rRNA) gene sequencing as the gold standard, 20 non‐duplicating anaerobic Gram positive bacilli isolated from blood cultures were analysed by the MicroSeq 500 16S rDNA bacterial identification system. The MicroSeq system successfully identified 13 of the 20 isolates. Four and three isolates were misidentified at the genus and species level, respectively. Although the MicroSeq 500 16S rDNA bacterial identification system is better than three commercially available identification systems also evaluated, its database needs to be expanded for accurate identification of anaerobic Gram positive bacilli. PMID:16443743
DNA G-quadruplexes in human telomeres and gene promoters are being extensively studied for their role in controlling the growth of cancer cells. Recent studies strongly suggest that guanine (G)-rich genes encoding pre-ribosomal RNA (pre-rRNA) are a potential anticancer target through the inhibition of RNA polymerase I (Pol I) in ribosome biogenesis. However, the structures of ribosomal G-quadruplexes at atomic resolution are unknown, and very little biophysical characterization has been performed on them to date. Here, we have modeled two putative rDNA G-quadruplex structures, NUC 19P and NUC 23P, which we observe via circular dichroism (CD) spectroscopy to adopt a predominantly parallel topology, and their counterpart rRNA. To validate and refine the putative ribosomal G-quadruplex structures, we performed all-atom molecular dynamics (MD) simulations using the CHARMM36 force field in the presence and absence of stabilizing K + or Na + ions. We optimized the CHARMM36 force field K + parameters to be more consistent with quantum mechanical calculations (and the polarizable Drude model force field) so that the K + ion is predominantly in the G-quadruplex channel. Our MD simulations show that the rDNA G-quadruplex have more well-defined, predominantly parallel-topology structures than rRNA and NUC 19P is more structured than NUC 23P, which features extended loops. Our study demonstrates that they are both potential targets for the design of novel chemotherapeutics.
Sobol, M. A.; Kordyum, E. L.
Fundamental discovery of gravisensitivity of cells no specified to gravity perception focused increasing attention on an elucidation of the mechanisms involved in altered gravity effects at the cellular and subcellular levels. The nucleolus is the transcription site of rRNA genes as well as the site of processing and initial packaging of their transcripts with ribosomal and nonribosomal proteins. The mechanisms inducing the changes in the subcomponents of the nucleolus that is morphologically defined yet highly dynamic structure are still unknown in detail. To understand the functional organization of the nucleolus as in the control as under altered gravity conditions it is essential to determine both the precise location of rDNA and the proteins playing the key role in rRNA processing. Lepidium sativum seeds were germinated in 1% agar medium on the slow horizontal clinostat (2 rpm) and in the stationary conditions. We investigated the root meristematic cells dissected from the seedlings grown in darkness for two days. The investigations were carried out with anti-DNA and anti-NopA100 antibodies labeling as well as with TdT procedure, and immunogold electron microscopy. In the stationary growth conditions, the anti-DNA antibody as well TdT procedure were capable of detecting fibrillar centers (FCs) and the dense fibrillar component (DFC) in the nucleolus. In FCs, gold particles were revealed on the condensed chromatin inclusions, internal fibrils of decondensed rDNA and the transition zone FC-DFC. Quantitatively, FCs appeared 1,5 times more densely labeled than DFC. NopA100 was localized in FCs and in DFC. In FCs, the most of protein was revealed in the transition zone FC-DFC. After a quantitative study, FCs and the transition zone FC-DFC appeared to contain NopA100 1,7 times more than DFC. Under the conditions of altered gravity, quantitative data clearly showed a redistribution of nucleolar DNA and NopA100 between FCs and DFC in comparison with the control. In
Wicke, Susann; Costa, Andrea; Muñoz, Jesùs; Quandt, Dietmar
Among eukaryotes two types of nuclear ribosomal DNA (nrDNA) organization have been observed. Either all components, i.e. the small ribosomal subunit, 5.8S, large ribosomal subunit, and 5S occur tandemly arranged or the 5S rDNA forms a separate cluster of its own. Generalizations based on data derived from just a few model organisms have led to a superimposition of structural and evolutionary traits to the entire plant kingdom asserting that plants generally possess separate arrays. This study reveals that plant nrDNA organization into separate arrays is not a distinctive feature, but rather assignable almost solely to seed plants. We show that early diverging land plants and presumably streptophyte algae share a co-localization of all rRNA genes within one repeat unit. This raises the possibility that the state of rDNA gene co-localization had occurred in their common ancestor. Separate rDNA arrays were identified for all basal seed plants and water ferns, implying at least two independent 5S rDNA transposition events during land plant evolution. Screening for 5S derived Cassandra transposable elements which might have played a role during the transposition events, indicated that this retrotransposon is absent in early diverging vascular plants including early fern lineages. Thus, Cassandra can be rejected as a primary mechanism for 5S rDNA transposition in water ferns. However, the evolution of Cassandra and other eukaryotic 5S derived elements might have been a side effect of the 5S rDNA cluster formation. Structural analysis of the intergenic spacers of the ribosomal clusters revealed that transposition events partially affect spacer regions and suggests a slightly different transcription regulation of 5S rDNA in early land plants. 5S rDNA upstream regulatory elements are highly divergent or absent from the LSU-5S spacers of most early divergent land plant lineages. Several putative scenarios and mechanisms involved in the concerted relocation of hundreds of 5S
Lobuglio, Katherine Frances
Cenococcum geophilum Fr., a cosmopolitan mycorrhizal fungus, is well-known for its extremely wide host and habitat range. The ecological diversity of C. geophilum sharply contrasts its present taxonomic status as a monotypic form -genus. Restriction fragment length polymorphisms (RFLPs) in nuclear ribosomal DNA (rDNA) was used to assess the degree of genetic variation among 72 isolates of C. geophilum. The probe used in this study was the rDNA repeat cloned from C. geophilum isolate A145 (pCG15). Length of the rDNA repeat was approximately 9 kb. The rDNA clone was mapped for 5 restriction endonucleases. Hybridization with cloned Saccharomyces cerevisiae rDNA (pSR118, and pSR125 containing the 18S, and 5.8-25S rRNA genes respectively), and alignment of restriction endonuclease sites conserved in the rDNA genes of other fungi, were used to position the corresponding rDNAs of C. geophilum. Southern hybridizations with EcoRI, HindIII, XhoI, and PstI digested DNAs indicated extensive variation among the C. geophilum isolates, greater than has been previously reported to occur within a fungal species. Most of the rDNA polymorphisms occurred in the IGS region. Restriction endonuclease site and length polymorphisms were also observed in the 5.8S-26S genic regions. Sixteen size categories of length mutations, 6 restriction endonuclease site additions, and 4 restriction endonuclease site deletions were determined using isolate A145 as a reference. The rDNA repeat length among the isolates varied from approximately 8.5 to 10.2 kb. RFLPs were also observed in the mitochondrial (mt) 24S rRNA gene and flanking regions of HindIII digested DNAs of C. geophilum isolates representing both geographically distinct and similar origins. Among the C. geophilum isolates analyzed there were fewer RFLPs in mt-DNA than in nuclear rDNA. EcoRI rDNA phenotypes between C. geophilum and Elaphomyces anthracinus, its proposed teleomorph or sexual state, did not correspond. In addition, the four
James, Stephen A.; O'Kelly, Michael J.T.; Carter, David M.; Davey, Robert P.; van Oudenaarden, Alexander; Roberts, Ian N.
Ribosomal DNA (rDNA) plays a key role in ribosome biogenesis, encoding genes for the structural RNA components of this important cellular organelle. These genes are vital for efficient functioning of the cellular protein synthesis machinery and as such are highly conserved and normally present in high copy numbers. In the baker's yeast Saccharomyces cerevisiae, there are more than 100 rDNA repeats located at a single locus on chromosome XII. Stability and sequence homogeneity of the rDNA array is essential for function, and this is achieved primarily by the mechanism of gene conversion. Detecting variation within these arrays is extremely problematic due to their large size and repetitive structure. In an attempt to address this, we have analyzed over 35 Mbp of rDNA sequence obtained from whole-genome shotgun sequencing (WGSS) of 34 strains of S. cerevisiae. Contrary to expectation, we find significant rDNA sequence variation exists within individual genomes. Many of the detected polymorphisms are not fully resolved. For this type of sequence variation, we introduce the term partial single nucleotide polymorphism, or pSNP. Comparative analysis of the complete data set reveals that different S. cerevisiae genomes possess different patterns of rDNA polymorphism, with much of the variation located within the rapidly evolving nontranscribed intergenic spacer (IGS) region. Furthermore, we find that strains known to have either structured or mosaic/hybrid genomes can be distinguished from one another based on rDNA pSNP number, indicating that pSNP dynamics may provide a reliable new measure of genome origin and stability. PMID:19141593
Dingman, Douglas W
Paenibacillus larvae is the causative agent of American foulbrood in honey bee (Apis mellifera) larvae. PCR amplification of the 16S-23S ribosomal DNA (rDNA) intergenic transcribed spacer (ITS) regions, and agarose gel electrophoresis of the amplified DNA, was performed using genomic DNA collected from 134 P. larvae strains isolated in Connecticut, six Northern Regional Research Laboratory stock strains, four strains isolated in Argentina, and one strain isolated in Chile. Following electrophoresis of amplified DNA, all isolates exhibited a common migratory profile (i.e., ITS-PCR fingerprint pattern) of six DNA bands. This profile represented a unique ITS-PCR DNA fingerprint that was useful as a fast, simple, and accurate procedure for identification of P. larvae. Digestion of ITS-PCR amplified DNA, using mung bean nuclease prior to electrophoresis, characterized only three of the six electrophoresis bands as homoduplex DNA and indicating three true ITS regions. These three ITS regions, DNA migratory band sizes of 915, 1010, and 1474 bp, signify a minimum of three types of rrn operons within P. larvae. DNA sequence analysis of ITS region DNA, using P. larvae NRRL B-3553, identified the 3' terminal nucleotides of the 16S rRNA gene, 5' terminal nucleotides of the 23S rRNA gene, and the complete DNA sequences of the 5S rRNA, tRNA(ala), and tRNA(ile) genes. Gene organization within the three rrn operon types was 16S-23S, 16S-tRNA(ala)-23S, and l6S-5S-tRNA(ile)-tRNA(ala)-23S and these operons were named rrnA, rrnF, and rrnG, respectively. The 23S rRNA gene was shown by I-CeuI digestion and pulsed-field gel electrophoresis of genomic DNA to be present as seven copies. This was suggestive of seven rrn operon copies within the P. larvae genome. Investigation of the 16S-23S rDNA regions of this bacterium has aided the development of a diagnostic procedure and has helped genomic mapping investigations via characterization of the ITS regions.
Bhattacharya, D; Damberger, S; Surek, B; Melkonian, M
The Zygnematales (Charophyta) contain a group-I intron (subgroupIC1) within their nuclear-encoded small subunit ribosomal DNA (SSU rDNA) coding region. This intron, which is inserted after position 1506 (relative to the SSU rDNA of Escherichia coli), is proposed to have been vertically inherited since the origin of the Zygnematales approximately 350-400 million years ago. Primary and secondary structure analyses were carried out to model group-I intron evolution in the Zygnematales. Secondary structure analyses support genetic data regarding sequence conservation within regions known to be functionally important for in vitro self-splicing of group-I introns. Comparisons of zygnematalean group-I intron secondary structures also provided some new insights into sequences that may have important roles in in vivo RNA splicing. Sequence analyses showed that sequence divergence rates and the nucleotide compositions of introns and coding regions within any one taxon varied widely, suggesting that the "1506" group-I introns and rDNA coding regions in the Zygnematales evolve independently.
Cabral-de-Mello, Diogo C; Cabrero, Josefa; López-León, María Dolores; Camacho, Juan Pedro M
We analyze the chromosomal location of 5S rDNA clusters in 29 species of grasshoppers belonging to the family Acrididae. There was extensive variation among species for the number and location of 5S rDNA sites. Out of 148 sites detected, 75% were proximally located, 21.6% were interstitial, and only 3.4% were distal. The number of 5S rDNA sites per species varied from a single chromosome pair (in six species) to all chromosome pairs (in five species), with a range of intermediate situations. Thirteen chromosomes from eight species carried two 5S rDNA clusters. At intraspecific level, differences among populations were detected in Eyprepocnemis plorans, and some heteromorphisms have also been observed in some species. Double FISH for 5S rDNA and H3 histone gene DNA, performed on 17 of these 29 species, revealed that both markers are sometimes placed in a same chromosome but at different location, whereas they appeared to co-localize in five species (Calliptamus barbarus, Heteracris adpersa, Aiolopus strepens, Oedipoda charpentieri and O. coerulescens). Double fiber-FISH in A. strepens and O. coerulescens showed that the two DNAs are closely interspersed with variable relative amounts of both classes of DNA. Finally, no correlation was observed between the number of 5S and 45S rDNA clusters in 23 species where this information was available. These results are discussed in the light of possible mechanisms of spread that led to the extensive variation in the number of clusters observed for both rDNA types in acridid grasshoppers.
Hershkovitz, M A; Zimmer, E A
The two internal transcribed spacers (ITS1 and ITS2) of nuclear ribosomal DNA have become commonly exploited sources of informative variation for interspecific-/intergeneric-level phylogenetic analyses among angiosperms and other eukaryotes. We present an alignment in which one-third to one-half of the ITS2 sequence is alignable above the family level in angiosperms and a phenetic analysis showing that ITS2 contains information sufficient to diagnose lineages at several hierarchical levels. Base compositional analysis shows that angiosperm ITS2 is inherently GC-rich, and that the proportion of T is much more variable than that for other bases. We propose a general model of angiosperm ITS2 secondary structure that shows common pairing relationships for most of the conserved sequence tracts. Variations in our secondary structure predictions for sequences from different taxa indicate that compensatory mutation is not limited to paired positions. PMID:8760866
Zillner, Karina; Filarsky, Michael; Rachow, Katrin; Weinberger, Michael; Längst, Gernot; Németh, Attila
The DNase I accessibility and chromatin organization of genes within the nucleus do correlate to their transcriptional activity. Here, we show that both serum starvation and overexpression of Tip5, a key regulator of ribosomal RNA gene (rDNA) repression, dictate DNase I accessibility, facilitate the association of rDNA with the nuclear matrix and thus regulate large-scale rDNA chromatin organization. Tip5 contains four AT-hooks and a TAM (Tip5/ARBP/MBD) domain, which were proposed to bind matrix-attachment regions (MARs) of the genome. Remarkably, the TAM domain of Tip5 functions as nucleolar localization and nuclear matrix targeting module, whereas AT-hooks do not mediate association with the nuclear matrix, but they are required for nucleolar targeting. These findings suggest a dual role for Tip5’s AT-hooks and TAM domain, targeting the nucleolus and anchoring to the nuclear matrix, and suggest a function for Tip5 in the regulation of higher-order rDNA chromatin structure. PMID:23580549
Calado, L L; Bertollo, L A C; Cioffi, M B; Costa, G W W F; Jacobina, U P; Molina, W F
Several chromosomal features of Gerreidae fish have been found to be conserved. In this group, it is unclear whether the high degree of chromosomal stasis is maintained when analyzing more dynamic regions of chromosomes, such as rDNA sites that generally show a higher level of variability. Thus, cytogenetic analyses were performed on 3 Atlantic species of the genus Eucinostomus using conventional banding (C-banding, Ag-NOR), AT- and GC-specific fluorochromes, and fluorescence in situ hybridization mapping of telomeric sequences and 5S and 18S rDNA sites. The results showed that although the karyotypical macrostructure of these species is similar (2n = 48 chromosomes, simple Ag-NORs seemingly located on homeologous chromosomes and centromeric heterochromatin pattern), there are differences in the positions of rDNA subunits 5S and 18S. Thus, the ribosomal sites have demonstrated to be effective cytotaxonomic markers in Eucinostomus, presenting a different evolutionary dynamics in relation to other chromosomal regions and allowing access to important evolutionary changes in this group.
da Rocha, Rafael Henrique; Baumgärtner, Lucas; Paiz, Leonardo Marcel; Margarido, Vladimir Pavan; Fernandes, Carlos Alexandre; Gubiani, Éder André
Abstract Corydoras Lacepède, 1803 is the most specious genus of Corydoradinae subfamily and many of its species are still unknown in relation to molecular cytogenetic markers. However, the diploid number and karyotypic formula were recorded for many species of this group. In current study, we provided the first cytogenetic information of Corydoras carlae Nijssen & Isbrücker, 1983, an endemic fish species from Iguassu River basin, Paraná State, Brazil. The individuals were collected in Florido River, a tributary of Iguassu River and analysed with respect to diploid number, heterochromatin distribution pattern, Ag-NORs and mapping of 5S and 18S ribosomal genes. The karyotype of this species comprises 46 chromosomes arranged in 22m+22sm+2st. The heterochromatin is distributed in centromeric and pericentromeric positions in most of the chromosomes, and also associated with NORs. The Ag-NORs were detected in the terminal position on the long arm of the metacentric pair 6. The double-FISH technique showed that 5S rDNA and 18S rDNA were co-localized in the terminal portion on the long arm of the metacentric pair 6. This condition of co-localization of ribosomal genes in Corydoras carlae seems to represent a marker for this species. PMID:28123681
Coleman, Annette W.
Nuclear rDNA Internal Transcribed Spacers, ITS1 and ITS2, are widely used for eukaryote phylogenetic studies from the ordinal level to the species level, and there is even a database for ITS2 sequences. However, ITS regions have been ignored in mammalian phylogenetic studies, and only a few rodent and ape sequences are represented in GenBank. The reasons for this dearth, and the remedies, are described here. We have recovered these sequences, mostly >1 kb in length, for 36 mammalian species. Sequence alignment and transcript folding comparisons reveal the rRNA transcript secondary structure. Mammalian ITS regions, though quite long, still fold into the recognizable secondary structure of other eukaryotes. The ITS2 in particular bears the four standard helix loops, and loops II and III have the hallmark characters universal to eukaryotes. Both sequence and insertions/deletions of transcript secondary structure helices observed here support the four superorder taxonomy of Placentalia. On the family level, major unique indels, neatly excising entire helices, will be useful when additional species are represented, resulting in significant further understanding of the details of mammalian evolutionary history. Furthermore, the identification of a highly conserved element of ITS1 common to warm-blooded vertebrates may aid in deciphering the complex mechanism of RNA transcript processing. This is the last major group of terrestrial vertebrates for which rRNA ITS secondary structure has been resolved. PMID:24260162
De Ley, Irma Tandingan; De Ley, Paul; Vierstraete, Andy; Karssen, Gerrit; Moens, Maurice; Vanfleteren, Jacques
Phylogenies were inferred from nearly complete small subunit (SSU) 18S rDNA sequences of 12 species of Meloidogyne and 4 outgroup taxa (Globodera pallida, Nacobbus abberans, Subanguina radicicola, and Zygotylenchus guevarai). Alignments were generated manually from a secondary structure model, and computationally using ClustalX and Treealign. Trees were constructed using distance, parsimony, and likelihood algorithms in PAUP* 4.0b4a. Obtained tree topologies were stable across algorithms and alignments, supporting 3 clades: clade I = [M. incognita (M. javanica, M. arenaria)]; clade II = M. duytsi and M. maritima in an unresolved trichotomy with (M. hapla, M. microtyla); and clade III = (M. exigua (M. graminicola, M. chitwoodi)). Monophyly of [(clade I, clade II) clade III] was given maximal bootstrap support (mbs). M. artiellia was always a sister taxon to this joint clade, while M. ichinohei was consistently placed with mbs as a basal taxon within the genus. Affinities with the outgroup taxa remain unclear, although G. pallida and S. radicicola were never placed as closest relatives of Meloidogyne. Our results show that SSU sequence data are useful in addressing deeper phylogeny within Meloidogyne, and that both M. ichinohei and M. artiellia are credible outgroups for phylogenetic analysis of speciations among the major species. PMID:19265950
Jack, Carmen V.; Cruz, Cristina; Hull, Ryan M.; Keller, Markus A.; Ralser, Markus; Houseley, Jonathan
Repeated regions are widespread in eukaryotic genomes, and key functional elements such as the ribosomal DNA tend to be formed of high copy repeated sequences organized in tandem arrays. In general, high copy repeats are remarkably stable, but a number of organisms display rapid ribosomal DNA amplification at specific times or under specific conditions. Here we demonstrate that target of rapamycin (TOR) signaling stimulates ribosomal DNA amplification in budding yeast, linking external nutrient availability to ribosomal DNA copy number. We show that ribosomal DNA amplification is regulated by three histone deacetylases: Sir2, Hst3, and Hst4. These enzymes control homologous recombination-dependent and nonhomologous recombination-dependent amplification pathways that act in concert to mediate rapid, directional ribosomal DNA copy number change. Amplification is completely repressed by rapamycin, an inhibitor of the nutrient-responsive TOR pathway; this effect is separable from growth rate and is mediated directly through Sir2, Hst3, and Hst4. Caloric restriction is known to up-regulate expression of nicotinamidase Pnc1, an enzyme that enhances Sir2, Hst3, and Hst4 activity. In contrast, normal glucose concentrations stretch the ribosome synthesis capacity of cells with low ribosomal DNA copy number, and we find that these cells show a previously unrecognized transcriptional response to caloric excess by reducing PNC1 expression. PNC1 down-regulation forms a key element in the control of ribosomal DNA amplification as overexpression of PNC1 substantially reduces ribosomal DNA amplification rate. Our results reveal how a signaling pathway can orchestrate specific genome changes and demonstrate that the copy number of repetitive DNA can be altered to suit environmental conditions. PMID:26195783
Lemaire, Benny; Huysmans, Suzy; Smets, Erik; Merckx, Vincent
Rate variation in genes from all three genomes has been observed frequently in plant lineages with a parasitic and mycoheterotrophic mode of life. While the loss of photosynthetic ability leads to a relaxation of evolutionary constraints in genes involved in the photosynthetic apparatus, it remains to be determined how prevalent increased substitution rates are in nuclear DNA of non-photosynthetic angiosperms. In this study we infer rates of molecular evolution of 18S rDNA of all parasitic and mycoheterotorphic plant families (except Lauraceae and Polygalaceae) using relative rate tests. In several holoparasitic and mycoheterotrophic plant lineages extremely high substitution rates are observed compared to other photosynthetic angiosperms. The position and frequency of these substitutions have been identified to understand the mutation dynamics of 18S rRNA in achlorophyllous plants. Despite the presence of significantly elevated substitution rates, very few mutations occur in major functional and structural regions of the small ribosomal molecule, providing evidence that the efficiency of the translational apparatus in non-photosynthetic plants has not been affected.
Perrin, A; Cetre-Sossah, C; Mathieu, B; Baldet, T; Delecolle, J-C; Albina, E
Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) play important roles in the transmission of viral diseases affecting wild and domestic ruminants and horses, including Bluetongue (BT) and African horse sickness (AHS) respectively. In southern Europe, BT has been largely transmitted by the classical Afro-Asian vector Culicoides imicola Kieffer. However, other species such as C. obsoletus Meigen, C. scoticus Downs & Kettle and C. pulicaris Linné may also be involved in BTV transmission. As a consequence of the discovery of C. imicola followed by BTV-2 outbreaks on the island of Corsica in October 2000, further studies on these biting midges have been carried out. To better characterize the evolution and phylogenetic relations of Culicoides, molecular analysis in parallel with a morphology-based taxonomic approach were performed. Phylogenetic analyses of French Culicoides species were undertaken using the ribosomal DNA (rDNA) internal transcribed spacer 1 (ITS1) as a molecular target. This region was shown to be useful in understanding evolutionary and genetic relationships between species. Construction of several trees showed that molecular phylogeny within the genus Culicoides correlates not only with morphological-based taxonomy but also with ecological patterns.
ALIX, JEAN-HERVÉ; NIERHAUS, KNUD H.
Assembly helpers exist for the formation of ribosomal subunits. Such a function has been suggested for the DnaK system of chaperones (DnaK, DnaJ, GrpE). Here we show that 50S and 30S ribosomal subunits from an Escherichia coli dnaK-null mutant (containing a disrupted dnaK gene) grown at 30°C are physically and functionally identical to wild-type ribosomes. Furthermore, ribosomal components derived from mutant 30S and 50S subunits are fully competent for in vitro reconstitution of active ribosomal subunits. On the other hand, the DnaK chaperone system cannot circumvent the necessary heat-dependent activation step for the in vitro reconstitution of fully active 30S ribosomal subunits. It is therefore questionable whether the requirement for DnaK observed during in vivo ribosome assembly above 37°C implicates a direct or indirect role for DnaK in this process. PMID:12810912
Cheng, Tian-Fan; Jia, Xiao-Ming; Ma, Xiao-Hang; Lin, Hai-Ping; Zhao, Yu-Hua
In this study, 18S rDNA and ITS-5.8S rDNA regions of four Shiraia bambusicola isolates collected from different species of bamboos were amplified by PCR with universal primer pairs NS1/NS8 and ITS5/ITS4, respectively, and sequenced. Phylogenetic analyses were conducted on three selected datasets of rDNA sequences. Maximum parsimony, distance and maximum likelihood criteria were used to infer trees. Morphological characteristics were also observed. The positioning of Shiraia in the order Pleosporales was well supported by bootstrap, which agreed with the placement by Amano (1980) according to their morphology. We did not find significant inter-hostal differences among these four isolates from different species of bamboos. From the results of analyses and comparison of their rDNA sequences, we conclude that Shiraia should be classified into Pleosporales as Amano (1980) proposed and suggest that it might be positioned in the family Phaeosphaeriaceae.
McGrath, K E; Smothers, J F; Dadd, C A; Madireddi, M T; Gorovsky, M A; Allis, C D
An abundant 52-kDa phosphoprotein was identified and characterized from macronuclei of the ciliated protozoan Tetrahymena thermophila. Immunoblot analyses combined with light and electron microscopic immunocytochemistry demonstrate that this polypeptide, termed Nopp52, is enriched in the nucleoli of transcriptionally active macronuclei and missing altogether from transcriptionally inert micronuclei. The cDNA sequence encoding Nopp52 predicts a polypeptide whose amino-terminal half consists of multiple acidic/serine-rich regions alternating with basic/proline-rich regions. Multiple serines located in these acidic stretches lie within casein kinase II consensus motifs, and Nopp52 is an excellent substrate for casein kinase II in vitro. The carboxyl-terminal half of Nopp52 contains two RNA recognition motifs and an extreme carboxyl-terminal domain rich in glycine, arginine, and phenylalanine, motifs common in many RNA processing proteins. A similar combination and order of motifs is found in vertebrate nucleolin and yeast NSR1, suggesting that Nopp52 is a member of a family of related nucleolar proteins. NSR1 and nucleolin have been implicated in transcriptional regulation of rDNA and rRNA processing. Consistent with a role in ribosomal gene metabolism, rDNA and Nopp52 colocalize in situ, as well as by cross-linking and immunoprecipitation experiments, demonstrating an association between Nopp52 and rDNA in vivo. Images PMID:9017598
Tremblay, Maxime; Toussaint, Martin; D'Amours, Annie; Conconi, Antonio
The genome is organized into nuclear domains, which create microenvironments that favor distinct chromatin structures and functions (e.g., highly repetitive sequences, centromeres, telomeres, noncoding sequences, inactive genes, RNA polymerase II and III transcribed genes, and the nucleolus). Correlations have been drawn between gene silencing and proximity to a heterochromatic compartment. At the other end of the scale are ribosomal genes, which are transcribed at a very high rate by RNA polymerase I (~60% of total transcription), have a loose chromatin structure, and are clustered in the nucleolus. The rDNA sequences have 2 distinct structures: active rRNA genes, which have no nucleosomes; and inactive rRNA genes, which have nucleosomes. Like DNA transcription and replication, DNA repair is modulated by the structure of chromatin, and the kinetics of DNA repair vary among the nuclear domains. Although research on DNA repair in all chromosomal contexts is important to understand the mechanisms of genome maintenance, this review focuses on nucleotide excision repair and photolyase repair of UV photoproducts in the first-order packing of DNA in chromatin: the nucleosome. In addition, it summarizes the studies that have demonstrated the existence of the 2 rDNA chromatins, and the way this feature of the rDNA locus allows for direct comparison of DNA repair in 2 very different structures: nucleosome and non-nucleosome DNA.
Lewinska, Anna; Miedziak, Beata; Kulak, Klaudia; Molon, Mateusz; Wnuk, Maciej
The nucleolus is speculated to be a regulator of cellular senescence in numerous biological systems (Guarente, Genes Dev 11(19):2449-2455, 1997; Johnson et al., Curr Opin Cell Biol 10(3):332-338, 1998). In the budding yeast Saccharomyces cerevisiae, alterations in nucleolar architecture, the redistribution of nucleolar protein and the accumulation of extrachromosomal ribosomal DNA circles (ERCs) during replicative aging have been reported. However, little is known regarding rDNA stability and changes in nucleolar activity during chronological aging (CA), which is another yeast aging model used. In the present study, the impact of aberrant cell cycle checkpoint control (knock-out of BUB1, BUB2, MAD1 and TEL1 genes in haploid and diploid hemizygous states) on CA-mediated changes in the nucleolus was studied. Nucleolus fragmentation, changes in the nucleolus size and the nucleolus/nucleus ratio, ERC accumulation, expression pattern changes and the relocation of protein involved in transcriptional silencing during CA were revealed. All strains examined were affected by oxidative stress, aneuploidy (numerical rather than structural aberrations) and DNA damage. However, the bub1 cells were the most prone to aneuploidy events, which may contribute to observed decrease in chronological lifespan. We postulate that chronological aging may be affected by redox imbalance-mediated chromosome XII instability leading to both rDNA instability and whole chromosome aneuploidy. CA-mediated nucleolus fragmentation may be a consequence of nucleolus enlargement and/or Nop2p upregulation. Moreover, the rDNA content of chronologically aging cells may be a factor determining the subsequent replicative lifespan. Taken together, we demonstrated that the nucleolus state is also affected during CA in yeast.
Rosato, Marcela; Moreno-Saiz, Juan C.; Galián, José A.; Rosselló, Josep A.
Several genome duplications have been identified in the evolution of seed plants, providing unique systems for studying karyological processes promoting diversification and speciation. Knowledge about the number of ribosomal DNA (rDNA) loci, together with their chromosomal distribution and structure, provides clues about organismal and molecular evolution at various phylogenetic levels. In this work, we aim to elucidate the evolutionary dynamics of karyological and rDNA site-number variation in all known taxa of subtribe Vellinae, showing a complex scenario of ancestral and more recent polyploid events. Specifically, we aim to infer the ancestral chromosome numbers and patterns of chromosome number variation, assess patterns of variation of both 45S and 5S rDNA families, trends in site-number change of rDNA loci within homoploid and polyploid series, and reconstruct the evolutionary history of rDNA site number using a phylogenetic hypothesis as a framework. The best-fitting model of chromosome number evolution with a high likelihood score suggests that the Vellinae core showing x = 17 chromosomes arose by duplication events from a recent x = 8 ancestor. Our survey suggests more complex patterns of polyploid evolution than previously noted for Vellinae. High polyploidization events (6x, 8x) arose independently in the basal clade Vella castrilensis–V. lucentina, where extant diploid species are unknown. Reconstruction of ancestral rDNA states in Vellinae supports the inference that the ancestral number of loci in the subtribe was two for each multigene family, suggesting that an overall tendency towards a net loss of 5S rDNA loci occurred during the splitting of Vellinae ancestors from the remaining Brassiceae lineages. A contrasting pattern for rDNA site change in both paleopolyploid and neopolyploid species was linked to diversification of Vellinae lineages. This suggests dynamic and independent changes in rDNA site number during speciation processes and a
Background Ribosomal 5S genes are well known for the critical role they play in ribosome folding and functionality. These genes are thought to evolve in a concerted fashion, with high rates of homogenization of gene copies. However, the majority of previous analyses regarding the evolutionary process of rDNA repeats were conducted in invertebrates and plants. Studies have also been conducted on vertebrates, but these analyses were usually restricted to the 18S, 5.8S and 28S rRNA genes. The recent identification of divergent 5S rRNA gene paralogs in the genomes of elasmobranches and teleost fishes indicate that the eukaryotic 5S rRNA gene family has a more complex genomic organization than previously thought. The availability of new sequence data from lower vertebrates such as teleosts and elasmobranches enables an enhanced evolutionary characterization of 5S rDNA among vertebrates. Results We identified two variant classes of 5S rDNA sequences in the genomes of Potamotrygonidae stingrays, similar to the genomes of other vertebrates. One class of 5S rRNA genes was shared only by elasmobranches. A broad comparative survey among 100 vertebrate species suggests that the 5S rRNA gene variants in fishes originated from rounds of genome duplication. These variants were then maintained or eliminated by birth-and-death mechanisms, under intense purifying selection. Clustered multiple copies of 5S rDNA variants could have arisen due to unequal crossing over mechanisms. Simultaneously, the distinct genome clusters were independently homogenized, resulting in the maintenance of clusters of highly similar repeats through concerted evolution. Conclusions We believe that 5S rDNA molecular evolution in fish genomes is driven by a mixed mechanism that integrates birth-and-death and concerted evolution. PMID:21627815
Fiore-Donno, Anna Maria; Kamono, Akiko; Meyer, Marianne; Schnittler, Martin; Fukui, Manabu; Cavalier-Smith, Thomas
The phylogenetic position of the slime-mould genus Lamproderma (Myxomycetes, Amoebozoa) challenges traditional taxonomy: although it displays the typical characters of the order Stemonitales, it appears to be sister to Physarales. This study provides a small subunit (18S or SSU) ribosomal RNA gene-based phylogeny of Lamproderma and its allies, with new sequences from 49 specimens in 12 genera. We found that the order Stemonitales and Lamproderma were both ancestral to Physarales and that Lamproderma constitutes several clades intermingled with species of Diacheopsis, Colloderma and Elaeomyxa. We suggest that these genera may have evolved from Lamproderma by multiple losses of fruiting body stalks and that many taxonomic revisions are needed. We found such high genetic diversity within three Lamproderma species that they probably consist of clusters of sibling species. We discuss the contrasts between genetic and morphological divergence and implications for the morphospecies concept, highlighting the phylogenetically most reliable morphological characters and pointing to others that have been overestimated. In addition, we showed that the first part (~600 bases) of the SSU rDNA gene is a valuable tool for phylogeny in Myxomycetes, since it displayed sufficient variability to distinguish closely related taxa and never failed to cluster together specimens considered of the same species.
Fiore-Donno, Anna Maria; Kamono, Akiko; Meyer, Marianne; Schnittler, Martin; Fukui, Manabu; Cavalier-Smith, Thomas
The phylogenetic position of the slime-mould genus Lamproderma (Myxomycetes, Amoebozoa) challenges traditional taxonomy: although it displays the typical characters of the order Stemonitales, it appears to be sister to Physarales. This study provides a small subunit (18S or SSU) ribosomal RNA gene-based phylogeny of Lamproderma and its allies, with new sequences from 49 specimens in 12 genera. We found that the order Stemonitales and Lamproderma were both ancestral to Physarales and that Lamproderma constitutes several clades intermingled with species of Diacheopsis, Colloderma and Elaeomyxa. We suggest that these genera may have evolved from Lamproderma by multiple losses of fruiting body stalks and that many taxonomic revisions are needed. We found such high genetic diversity within three Lamproderma species that they probably consist of clusters of sibling species. We discuss the contrasts between genetic and morphological divergence and implications for the morphospecies concept, highlighting the phylogenetically most reliable morphological characters and pointing to others that have been overestimated. In addition, we showed that the first part (∼600 bases) of the SSU rDNA gene is a valuable tool for phylogeny in Myxomycetes, since it displayed sufficient variability to distinguish closely related taxa and never failed to cluster together specimens considered of the same species. PMID:22530009
Jakočiūnas, Tadas; Domange Jordö, Marie; Aït Mebarek, Mazhoura; Bünner, Camilla Marie; Verhein-Hansen, Janne; Oddershede, Lene B.; Thon, Geneviève
Our research addresses the relationship between subnuclear localization and gene expression in fission yeast. We observed the relocalization of a heterochromatic region, the mating-type region, from its natural location at the spindle-pole body to the immediate vicinity of the nucleolus. Relocalization occurred in response to a DNA rearrangement replacing a boundary element (IR-R) with a ribosomal DNA repeat (rDNA-R). Gene expression was strongly silenced in the relocalized mating-type region through mechanisms that differ from those operating in wild type. Also different from the wild-type situation, programmed recombination events failed to take place in the rDNA-R mutant. Increased silencing and perinucleolar localization depended on Reb1, a DNA-binding protein with cognate sites in the rDNA. Reb1 was recently shown to mediate long-range interchromosomal interactions in the nucleus through dimerization, providing a mechanism for the observed relocalization. Replacing the full rDNA repeat with Reb1-binding sites, and using mutants lacking the histone H3K9 methyltransferase Clr4, indicated that the relocalized region was silenced redundantly by heterochromatin and another mechanism, plausibly antisense transcription, achieving a high degree of repression in the rDNA-R strain. PMID:24191010
Hoshina, Ryo; Kamako, Shin-ichiro; Imamura, Nobutaka
In the nuclear encoded small subunit ribosomal DNA (18S rDNA) of symbiotic alga of Paramecium bursaria (F36 collected in Japan) possesses three intron-like insertions (Hoshina et al., unpubl. data, 2003). The present study confirmed these exact lengths and insertion sites by reverse transcription-PCR. Two of them were inserted at Escherichia coli 16S rRNA genic position 943 and 1512 that are frequent intron insertion positions, but another insertion position (nearly 1370) was the first finding. Their secondary structures suggested they belong to Group-I intron; one belongs to subgroup IE, others belong to subgroup IC1. Similarity search indicated these introns are ancestral ones.
Kazi, Mudassar Anisoddin; Reddy, C R K; Jha, Bhavanath
The biodiversity assessment of different taxa of the genus Caulerpa is of interest from the context of morphological plasticity, invasive potential of some species and biotechnological and pharmacological applications. The present study investigated the identification and molecular phylogeny of different species of Caulerpa occurring along the Indian coast inferred from tufA, rbcL, 18S rDNA and ITS rDNA nucleotide sequences. Molecular data confirmed the identification of 10 distinct Caulerpa species: C. veravalensis, C. verticillata, C. racemosa, C. microphysa, C. taxifolia, C. sertularioides, C. scalpelliformis, C. serrulata, C. peltata and C. mexicana. All datasets significantly supported the sister relationship between C. veravalensis and C. racemosa var. cylindracea. It was also concluded from the results that the specimen identified previously as C. microphysa and C. lentillifera could not be considered as separate species. The molecular data revealed the presence of multiple lineages for C. racemosa which can be resolved into separate species. All four markers were used to ascertain their utility for DNA barcoding. The tufA gene proved a better marker with monophyletic association as the main criteria for identification at the species level. The results also support the use of 18S rDNA insertion sequences to delineate the Caulerpa species through character-based barcoding. The ITS rDNA (5.8S-ITS2) phylogenetic analysis also served as another supporting tool. Further, more sequences from additional Caulerpa specimens will need to be analysed in order to support the role of these two markers (ITS rDNA and 18S insertion sequence) in identification of Caulerpa species. The present study revealed the phylogeny of Caulerpa as complete as possible using the currently available data, which is the first comprehensive report illustrating the molecular phylogeny and barcoding of the genus Caulerpa from Indian waters.
Kazi, Mudassar Anisoddin; Reddy, C. R. K.; Jha, Bhavanath
The biodiversity assessment of different taxa of the genus Caulerpa is of interest from the context of morphological plasticity, invasive potential of some species and biotechnological and pharmacological applications. The present study investigated the identification and molecular phylogeny of different species of Caulerpa occurring along the Indian coast inferred from tufA, rbcL, 18S rDNA and ITS rDNA nucleotide sequences. Molecular data confirmed the identification of 10 distinct Caulerpa species: C. veravalensis, C. verticillata, C. racemosa, C. microphysa, C. taxifolia, C. sertularioides, C. scalpelliformis, C. serrulata, C. peltata and C. mexicana. All datasets significantly supported the sister relationship between C. veravalensis and C. racemosa var. cylindracea. It was also concluded from the results that the specimen identified previously as C. microphysa and C. lentillifera could not be considered as separate species. The molecular data revealed the presence of multiple lineages for C. racemosa which can be resolved into separate species. All four markers were used to ascertain their utility for DNA barcoding. The tufA gene proved a better marker with monophyletic association as the main criteria for identification at the species level. The results also support the use of 18S rDNA insertion sequences to delineate the Caulerpa species through character-based barcoding. The ITS rDNA (5.8S-ITS2) phylogenetic analysis also served as another supporting tool. Further, more sequences from additional Caulerpa specimens will need to be analysed in order to support the role of these two markers (ITS rDNA and 18S insertion sequence) in identification of Caulerpa species. The present study revealed the phylogeny of Caulerpa as complete as possible using the currently available data, which is the first comprehensive report illustrating the molecular phylogeny and barcoding of the genus Caulerpa from Indian waters. PMID:24340028
Horvat, Tomislav; Maglica, Željka; Vojta, Aleksandar; Zoldoš, Vlatka
Around 2200 copies of genes encoding ribosomal RNA (rRNA) in pedunculate oak, Quercus robur, are organized into two rDNA loci, the major (NOR-1) and the minor (NOR-2) locus. We present the first cytogenetic evidence indicating that the NOR-1 represents the active nucleolar organizer responsible for rRNA synthesis, while the NOR-2 probably stays transcriptionally silent and does not participate in the formation of the nucleolus in Q. robur, which is a situation resembling the well-known phenomenon of nucleolar dominance. rDNA chromatin topology analyses in cycling root tip cells by light and electron microscopy revealed the minor locus to be highly condensed and located away from the nucleolus, while the major locus was consistently associated with the nucleolus and often exhibited different levels of condensation. In addition, silver precipitation was confined exclusively to the NOR-1 locus. Also, NOR-2 was highly methylated at cytosines and rDNA chromatin was marked with histone modifications characteristic for repressive state. After treatment of the root cells with the methylation inhibitor 5-aza-2′-deoxycytidine, we observed an increase in the total level of rRNA transcripts and a decrease in DNA methylation level at the NOR-2 locus. Also, NOR-2 sites relocalized with respect to the nuclear periphery/nucleolus, however, the relocation did not affect the contribution of this locus to nucleolar formation, nor did it affect rDNA chromatin decondensation, strongly suggesting that NOR-2 has lost the function of rRNA synthesis and nucleolar organization. PMID:25093501
Curran, Stephen S; Pulis, Eric E; Hugg, Dennis O; Brown, Jessica P; Manuel, Lynnae C; Overstreet, Robin M
The infrequently reported allocreadiid digenean Creptotrema funduli Mueller, 1934 is documented from the blackstripe topminnow, Fundulus notatus (Cyprinodontiformes: Fundulidae), in the headwaters of the Biloxi River, Harrison County, Mississippi. Specimens from Mississippi were compared with the type material from Fundulus diaphanus menona from Oneida Lake, New York, and no substantial difference was found. A fragment of ribosomal DNA, comprising a short portion of the 3' end of 18S nuclear rDNA gene, internal transcribed spacer (ITS) genes (including ITS1, 5.8S, and ITS2), and the 5' end of the 28S gene including variable domains D1-D3 was sequenced for the species. A portion of the 28S rDNA gene from C. funduli, plus similar fragments from 8 other allocreadiids and the callodistomatid Prosthenhystera sp., were aligned and subjected to maximum likelihood and Bayesian inference analyses. Resulting phylogenetic trees were derived from the analyses and used to estimate the relationship of Creptotrema Travassos, Artigas, and Pereira, 1928 with other allocreadiids. Creptotrema was found to be closely related to Megalogonia Surber, 1928 and 3 Neotropical genera, i.e., Wallinia Pearse, 1920, Creptotrematina Yamaguti, 1954, and Auriculostoma Scholz, Aguirre-Macedo, and Choudhury, 2004. No molecular data were available for species in Creptotrema prior to this study, so the ITS1, 5.8S, and ITS2 genes have been made available for comparative studies involving neotropical species in the genus.
Albert, Benjamin; Hafner, Lukas; Lezaja, Aleksandra; Costanzo, Michael; Boone, Charlie; Shore, David
The Rif1 protein is a negative regulator of DNA replication initiation in eukaryotes. Here we show that budding yeast Rif1 inhibits DNA replication initiation at the rDNA locus. Absence of Rif1, or disruption of its interaction with PP1/Glc7 phosphatase, leads to more intensive rDNA replication. The effect of Rif1-Glc7 on rDNA replication is similar to that of the Sir2 deacetylase, and the two would appear to act in the same pathway, since the rif1Δ sir2Δ double mutant shows no further increase in rDNA replication. Loss of Rif1-Glc7 activity is also accompanied by an increase in rDNA repeat instability that again is not additive with the effect of sir2Δ. We find, in addition, that the viability of rif1Δ cells is severely compromised in combination with disruption of the MRX or Ctf4-Mms22 complexes, both of which are implicated in stabilization of stalled replication forks. Significantly, we show that removal of the rDNA replication fork barrier (RFB) protein Fob1, alleviation of replisome pausing by deletion of the Tof1/Csm3 complex, or a large deletion of the rDNA repeat array all rescue this synthetic growth defect of rif1Δ cells lacking in addition either MRX or Ctf4-Mms22 activity. These data suggest that the repression of origin activation by Rif1-Glc7 is important to avoid the deleterious accumulation of stalled replication forks at the rDNA RFB, which become lethal when fork stability is compromised. Finally, we show that Rif1-Glc7, unlike Sir2, has an important effect on origin firing outside of the rDNA locus that serves to prevent activation of the DNA replication checkpoint. Our results thus provide insights into a mechanism of replication control within a large repetitive chromosomal domain and its importance for the maintenance of genome stability. These findings may have important implications for metazoans, where large blocks of repetitive sequences are much more common. PMID:27820830
Díaz-Nieto, Leonardo M.; Maciá, Arnaldo; Parisi, Gustavo; Farina, Juan L.; Vidal-Domínguez, María E.; Perotti, M. Alejandra; Berón, Corina M.
Although Mar del Plata is the most important city on the Atlantic coast of Argentina, mosquitoes inhabiting such area are almost uncharacterized. To increase our knowledge in their distribution, we sampled specimens of natural populations. After the morphological identification based on taxonomic keys, sequences of DNA from small ribosomal subunit (18S rDNA) and cytochrome c oxidase I (COI) genes were obtained from native species and the phylogenetic analysis of these sequences were done. Fourteen species from the genera Uranotaenia, Culex, Ochlerotatus and Psorophora were found and identified. Our 18S rDNA and COI-based analysis indicates the relationships among groups at the supra-species level in concordance with mosquito taxonomy. The introduction and spread of vectors and diseases carried by them are not known in Mar del Plata, but some of the species found in this study were reported as pathogen vectors. PMID:24098700
Poggio, María Georgina; Bressa, María José; Papeschi, Alba Graciela
Abstract In the present work, we analysed the male meiosis, the content and distribution of heterochromatin and the number and location of nucleolus organizing regions in Microtomus lunifer (Berg, 1900) by means of standard technique, C- and fluorescent bandings, and fluorescent in situ hybridization with an 18S rDNA probe. This species is the second one cytogenetically analysed within the Hammacerinae. Its male diploid chromosome number is 31 (2n=28+X1X2Y), including a minute pair of m-chromosomes. The diploid autosomal number and the presence of m-chromosomes are similar to those reported in Microtomus conspicillaris (Drury, 1782) (2n=28+XY). However, Microtomus lunifer has a multiple sex chromosome system X1X2Y (male) that could have originated by fragmentation of the ancestral X chromosome. Taking into account that Microtomus conspicillaris and Microtomus lunifer are the only two species within Reduviidae that possess m-chromosomes, the presence of this pair could be a synapomorphy for the species of this genus. C- and fluorescent bandings showed that the amount of heterochromatin in Microtomus lunifer was small, and only a small CMA3 bright band was observed in the largest autosomal pair at one terminal region. FISH with the 18S rDNA probe demonstrated that ribosomal genes were terminally placed on the largest autosomal pair. Our present results led us to propose that the location of rDNA genes could be associated with variants of the sex chromosome systems in relation with a kind of the sex chromosome systems within this family. Furthermore, the terminal location of NOR in the largest autosomal pair allowed us to use it as a chromosome marker and, thus, to infer that the kinetic activity of both ends is not a random process, and there is an inversion of this activity. PMID:24260616
Redberg, G.L.; Hibbett, D.S.; Ammirati, J.F.; Rodriguez, R.J.
The genetic diversity and phylogeny of Bridgeoporus nobilissimus have been analyzed. DNA was extracted from spores collected from individual fruiting bodies representing six geographically distinct populations in Oregon and Washington. Spore samples collected contained low levels of bacteria, yeast and a filamentous fungal species. Using taxon-specific PCR primers, it was possible to discriminate among rDNA from bacteria, yeast, a filamentous associate and B. nobilissimus. Nuclear rDNA internal transcribed spacer (ITS) region sequences of B. nobilissimus were compared among individuals representing six populations and were found to have less than 2% variation. These sequences also were used to design dual and nested PCR primers for B. nobilissimus-specific amplification. Mitochondrial small-subunit rDNA sequences were used in a phylogenetic analysis that placed B. nobilissimus in the hymenochaetoid clade, where it was associated with Oxyporus and Schizopora.
Machida, Ryuji J.; Knowlton, Nancy
Background Metagenetic analyses, which amplify and sequence target marker DNA regions from environmental samples, are increasingly employed to assess the biodiversity of communities of small organisms. Using this approach, our understanding of microbial diversity has expanded greatly. In contrast, only a few studies using this approach to characterize metazoan diversity have been reported, despite the fact that many metazoan species are small and difficult to identify or are undescribed. One of the reasons for this discrepancy is the availability of universal primers for the target taxa. In microbial studies, analysis of the 16S ribosomal DNA is standard. In contrast, the best gene for metazoan metagenetics is less clear. In the present study, we have designed primers that amplify the nuclear 18S and 28S ribosomal DNA sequences of most metazoan species with the goal of providing effective approaches for metagenetic analyses of metazoan diversity in environmental samples, with a particular emphasis on marine biodiversity. Methodology/Principal Findings Conserved regions suitable for designing PCR primers were identified using 14,503 and 1,072 metazoan sequences of the nuclear 18S and 28S rDNA regions, respectively. The sequence similarity of both these newly designed and the previously reported primers to the target regions of these primers were compared for each phylum to determine the expected amplification efficacy. The nucleotide diversity of the flanking regions of the primers was also estimated for genera or higher taxonomic groups of 11 phyla to determine the variable regions within the genes. Conclusions/Significance The identified nuclear ribosomal DNA primers (five primer pairs for 18S and eleven for 28S) and the results of the nucleotide diversity analyses provide options for primer combinations for metazoan metagenetic analyses. Additionally, advantages and disadvantages of not only the 18S and 28S ribosomal DNA, but also other marker regions as targets
Vershinina, Alisa O.; Anokhin, Boris A.; Lukhtanov, Vladimir A.
Abstract Ribosomal DNA clusters and telomeric repeats are important parts of eukaryotic genome. However, little is known about their organization and localization in karyotypes of organisms with holocentric chromosomes. Here we present first cytogenetic study of these molecular structures in seven blue butterflies of the genus Polyommatus Latreille, 1804 with low and high chromosome numbers (from n=10 to n=ca.108) using fluorescence in situ hybridization (FISH) with 18S rDNA and (TTAGG)n telomeric probes. FISH with the 18S rDNA probe showed the presence of two different variants of the location of major rDNA clusters in Polyommatus species: with one or two rDNA-carrying chromosomes in haploid karyotype. We discuss evolutionary trends and possible mechanisms of changes in the number of ribosomal clusters. We also demonstrate that Polyommatus species have the classical insect (TTAGG)n telomere organization. This chromosome end protection mechanism probably originated de novo in small chromosomes that evolved via fragmentations. PMID:26140159
Calixto, Merilane da Silva; de Andrade, Izaquiel Santos; Cabral-de-Mello, Diogo Cavalcanti; Santos, Neide; Martins, Cesar; Loreto, Vilma; de Souza, Maria José
Chromosomal organization and the evolution of genome architecture can be investigated by physical mapping of the genes for 45S and 5S ribosomal DNAs (rDNAs) and by the analysis of telomeric sequences. We studied 12 species of bats belonging to four subfamilies of the family Phyllostomidae in order to correlate patterns of distribution of heterochromatin and the multigene families for rDNA. The number of clusters for 45S gene ranged from one to three pairs, with exclusively location in autosomes, except for Carollia perspicillata that had in X chromosome. The 5S gene all the species studied had only one site located on an autosomal pair. In no species the 45S and 5S genes collocated. The fluorescence in situ hybridization (FISH) probe for telomeric sequences revealed fluorescence on all telomeres in all species, except in Carollia perspicillata. Non-telomeric sites in the pericentromeric region of the chromosomes were observed in most species, ranged from one to 12 pairs. Most interstitial telomeric sequences were coincident with heterochromatic regions. The results obtained in the present work indicate that different evolutionary mechanisms are acting in Phyllostomidae genome architecture, as well as the occurrence of Robertsonian fusion during the chromosomal evolution of bats without a loss of telomeric sequences. These data contribute to understanding the organization of multigene families and telomeric sequences on bat genome as well as the chromosomal evolutionary history of Phyllostomidae bats.
Valenzuela-González, Fabiola; Martínez-Porchas, Marcel; Villalpando-Canchola, Enrique; Vargas-Albores, Francisco
Ultrafast-metagenomic sequence classification using exact alignments (Kraken) is a novel approach to classify 16S rDNA sequences. The classifier is based on mapping short sequences to the lowest ancestor and performing alignments to form subtrees with specific weights in each taxon node. This study aimed to evaluate the classification performance of Kraken with long 16S rDNA random environmental sequences produced by cloning and then Sanger sequenced. A total of 480 clones were isolated and expanded, and 264 of these clones formed contigs (1352 ± 153 bp). The same sequences were analyzed using the Ribosomal Database Project (RDP) classifier. Deeper classification performance was achieved by Kraken than by the RDP: 73% of the contigs were classified up to the species or variety levels, whereas 67% of these contigs were classified no further than the genus level by the RDP. The results also demonstrated that unassembled sequences analyzed by Kraken provide similar or inclusively deeper information. Moreover, sequences that did not form contigs, which are usually discarded by other programs, provided meaningful information when analyzed by Kraken. Finally, it appears that the assembly step for Sanger sequences can be eliminated when using Kraken. Kraken cumulates the information of both sequence senses, providing additional elements for the classification. In conclusion, the results demonstrate that Kraken is an excellent choice for use in the taxonomic assignment of sequences obtained by Sanger sequencing or based on third generation sequencing, of which the main goal is to generate larger sequences.
Colomba, Mariastella; Vitturi, Roberto; Volpe, Nicola; Lannino, Antonella; Zunino, Mario
Six specimens of Anoplotrupes stercorosus (Coleoptera Scarabaeoidea: Geotrupidae) were analysed using conventional staining, banding techniques and fluorescent in situ hybridization with a ribosomal probe (rDNA FISH). Detailed karyotype description was also joined to a comparative analysis between present data and those previously reported for Thorectes intermedius [Chromosome Res. 7 (1999) 1]. The two species, both belonging to the tribe Geotrupini, show the same modal number but different autosomal morphology which is in contrast with the high chromosome stability argued for Geotrupinae during the last three decades. Moreover, a detailed comparison reveals the occurrence of a plesiomorphic condition in A. stercorosus with respect to the apomorphic one of T. intermedius. This finding agrees with phylogenetic relationships proposed for the two genera based on morphological and anatomical characters.
Nose, Mine; Miyahara, Fumihiko; Ohira, Mineko; Matsunaga, Koji; Tobase, Masashi; Koyama, Takao; Yoshimoto, Kikuo
Ribosomal DNA region sequences (partial 18S, 28S and complete ITS1, 5.8S, and ITS2) of the pinewood nematode (Bursaphelenchus xylophilus) were obtained from DNA extracted directly from wood pieces collected from wilted pine trees throughout the Kyushu and Okinawa islands, Japan. Either a 2569bp or 2573bp sequence was obtained from 88 of 143 samples. Together with the 45 rDNA sequences of pinewood nematode isolates previously reported, there were eight single nucleotide polymorphisms and two indels of two bases. Based on these mutations, nine haplotypes were estimated. The haplotype frequencies differed among regions in Kyushu island (northwest, northeast and center, southeast, and southwest), and the distribution was consistent with the invasion and spreading routes of the pinewood nematode previously estimated from past records of pine wilt and wood importation. There was no significant difference in haplotype frequencies among the collection sites on Okinawa island. PMID:22736814
Kusnadi, Eric P; Hannan, Katherine M; Hicks, Rodney J; Hannan, Ross D; Pearson, Richard B; Kang, Jian
Exquisite control of ribosome biogenesis is fundamental for the maintenance of cellular growth and proliferation. Importantly, synthesis of ribosomal RNA by RNA polymerase I is a key regulatory step in ribosome biogenesis and a major biosynthetic and energy consuming process. Consequently, ribosomal RNA gene transcription is tightly coupled to the availability of growth factors, nutrients and energy. Thus cells have developed an intricate sensing network to monitor the cellular environment and modulate ribosomal DNA transcription accordingly. Critical controllers in these sensing networks, which mediate growth factor activation of ribosomal DNA transcription, include the PI3K/AKT/mTORC1, RAS/RAF/ERK pathways and MYC transcription factor. mTORC1 also responds to amino acids and energy status, making it a key hub linking all three stimuli to the regulation of ribosomal DNA transcription, although this is achieved via overlapping and distinct mechanisms. This review outlines the current knowledge of how cells respond to environmental cues to control ribosomal RNA synthesis. We also highlight the critical points within this network that are providing new therapeutic opportunities for treating cancers through modulation of RNA polymerase I activity and potential novel imaging strategies.
Fredsøe, Jacob; Nielsen, Ida; Pedersen, Jakob Madsen; Bentsen, Iben Bach; Lisby, Michael; Bjergbaek, Lotte; Andersen, Anni H
Faithful DNA replication with correct termination is essential for genome stability and transmission of genetic information. Here we have investigated the potential roles of Topoisomerase II (Top2) and the RecQ helicase Sgs1 during late stages of replication. We find that cells lacking Top2 and Sgs1 (or Top3) display two different characteristics during late S/G2 phase, checkpoint activation and accumulation of asymmetric X-structures, which are both independent of homologous recombination. Our data demonstrate that checkpoint activation is caused by a DNA structure formed at the strongest rDNA replication fork barrier (RFB) during replication termination, and consistently, checkpoint activation is dependent on the RFB binding protein, Fob1. In contrast, asymmetric X-structures are formed independent of Fob1 at less strong rDNA replication fork barriers. However, both checkpoint activation and formation of asymmetric X-structures are sensitive to conditions, which facilitate fork merging and progression of replication forks through replication fork barriers. Our data are consistent with a redundant role of Top2 and Sgs1 together with Top3 (Sgs1-Top3) in replication fork merging at rDNA barriers. At RFB either Top2 or Sgs1-Top3 is essential to prevent formation of a checkpoint activating DNA structure during termination, but at less strong rDNA barriers absence of the enzymes merely delays replication fork merging, causing an accumulation of asymmetric termination structures, which are solved over time. PMID:26630413
Giribet, G; Carranza, S; Riutort, M; Baguñà, J; Ribera, C
The internal phylogeny of the 'myriapod' class Chilopoda is evaluated for 12 species belonging to the five extant centipede orders, using 18S rDNA complete gene sequence and 28S rDNA partial gene sequence data. Equally and differentially weighted parsimony, neighbour-joining and maximum-likelihood were used for phylogenetic reconstruction, and bootstrapping and branch support analyses were performed to evaluate tree topology stability. The results show that the Chilopoda constitute a monophyletic group that is divided into two lines, Notostigmophora (= Scutigeromorpha) and Pleurostigmophora, as found in previous morphological analyses. The Notostigmophora are markedly modified for their epigenic mode of life. The first offshoot of the Pleurostigmophora are the Lithobiomorpha, followed by the Craterostigmomorpha and by the Epimorpha s. str. (= Scolopendromorpha + Geophilomorpha), although strong support for the monophyly of the Epimorpha s. lat. (= Craterostigmomorpha + Epimorpha s. str.) is only found in the differentially weighted parsimony analysis. PMID:10087567
Fujiwara, H; Ogura, T; Takada, N; Miyajima, N; Ishikawa, H; Maekawa, H
We obtained two different clones (16 kb and 13 kb) of B. mori rDNA with intron sequence within the 28S-rRNA coding region. The sequence surrounding the intron was found to be highly conserved as indicated in several eukaryotes (Tetrahymena, Drosophila and Xenopus). The 28S rRNA-coding sequence of 16 kb and 13 kb clone was interrupted at precisely the same sites as those where the D. melanogaster rDNA interrupted by the type I and type II intron, respectively. The intron sequences of B. mori were different from those of D. melanogaster. In 16 kb clone, the intron was flanked by 14 bp duplication of the junction sequence, which was also present once within the 28S rRNA-coding region of rDNA without intron. This 14 bp sequence was identical with those surrounding the introns of Dipteran rDNAs. PMID:6091041
Cruz, V P; Oliveira, C; Foresti, F
5S rDNA genes of the stingray Potamotrygon motoro were PCR replicated, purified, cloned and sequenced. Two distinct classes of segments of different sizes were obtained. The smallest, with 342 bp units, was classified as class I, and the largest, with 1900 bp units, was designated as class II. Alignment with the consensus sequences for both classes showed changes in a few bases in the 5S rDNA genes. TATA-like sequences were detected in the nontranscribed spacer (NTS) regions of class I and a microsatellite (GCT) 10 sequence was detected in the NTS region of class II. The results obtained can help to understand the molecular organization of ribosomal genes and the mechanism of gene dispersion.
Gomez-Rodriguez, Victor Manuel; Rodriguez-Garay, Benjamin; Palomino, Guadalupe; Martínez, Javier; Barba-Gonzalez, Rodrigo
Abstract Agave Linnaeus, 1753 is endemic of America and is considered one of the most important crops in Mexico due to its key role in the country’s economy. Cytogenetic analysis was carried out in Agave tequilana Weber, 1902 ‘Azul’, Agave cupreata Trelease et Berger, 1915 and Agave angustifolia Haworth, 1812. The analysis showed that in all species the diploid chromosome number was 2n = 60, with bimodal karyotypes composed of five pairs of large chromosomes and 25 pairs of small chromosomes. Furthermore, different karyotypical formulae as well as a secondary constriction in a large chromosome pair were found in all species. Fluorescent in situ hybridization (FISH) was used for physical mapping of 5S and 18S ribosomal DNA (rDNA). All species analyzed showed that 5S rDNA was located in both arms of a small chromosome pair, while 18S rDNA was associated with the secondary constriction of a large chromosome pair. Data of FISH analysis provides new information about the position and number of rDNA loci and helps for detection of hybrids in breeding programs as well as evolutionary studies. PMID:24260700
Ferris, V. R.; Krall, E.; Faghihi, J.; Ferris, J. M.
Globodera millefolii and G. artemisiae are interesting because their type localities (Estonia and Russia, respectively) are geographically distant from those of the potato cyst nematodes and other Globodera species that seem to have originated in the Western world, and because the type host for each is a member of Compositae rather than Solanaceae. Sequence data for ITS1, ITS2, and 5.8S ribosomal DNA (ITS rDNA) for G. millefolii and G. artemisiae were nearly identical to sequence data for Cactodera salina from the rhizosphere of the estuary plant Salicornia bigelovii in Sonora, Mexico. The ITS rDNA sequences of these three species were all about 94% similar to those of two other Cactodera species for which ITS rDNA data were obtained. Phylogenetic analysis indicated that, based on the ITS rDNA data, G. millefolii and G. artemisiae are more closely related phylogenetically to the Cactodera species than to other nominal Globodera species. The molecular data further suggest that the genus Cactodera may comprise two or more morphologically similar but separate groups. PMID:19270922
Mejia-Madrid, H H; Aguirre-Macedo, M L
The molecular characterization of the daniconematid dracunculoid Mexiconema cichlasomae Moravec, Vidal, and Salgado-Maldonado, 1992 through the sequencing of SSU rDNA from adult individuals is presented herein. Additionally, preliminary genetic relationships of this nematode are inferred from alignment of sequences generated previously for other dracunculoids. Maximum parsimony and maximum likelihood analyses recovered identical trees. As anticipated by previous taxonomic work, M. cichlasomae is putatively closely related to skrjabillanid dracunculoids represented by Molnaria intestinalis (Dogiel and Bychovsky, 1934) and Skrjabillanus scardinii Molnár, 1966 SSU rDNA sequences, but the relationships of this newly discovered clade to other dracunculoid clades remain unresolved.
Fikru, Regassa; Matetovici, Irina; Rogé, Stijn; Merga, Bekana; Goddeeris, Bruno Maria; Büscher, Philippe; Van Reet, Nick
Animal trypanosomosis caused by Trypanosoma vivax (T. vivax) is a devastating disease causing serious economic losses. Most molecular diagnostics for T. vivax infection target the ribosomal DNA locus (rDNA) but are challenged by the heterogeneity among T. vivax strains. In this study, we investigated the rDNA heterogeneity of Ethiopian T. vivax strains in relation to their presence in tsetse-infested and tsetse-free areas and its effect on molecular diagnosis. We sequenced the rDNA loci of six Ethiopian (three from tsetse-infested and three from tsetse-free areas) and one Nigerian T. vivax strain. We analysed the obtained sequences in silico for primer-mismatches of some commonly used diagnostic PCR assays and for GC content. With these data, we selected some rDNA diagnostic PCR assays for evaluation of their diagnostic accuracy. Furthermore we constructed two phylogenetic networks based on sequences within the smaller subunit (SSU) of 18S and within the 5.8S and internal transcribed spacer 2 (ITS2) to assess the relatedness of Ethiopian T. vivax strains to strains from other African countries and from South America. In silico analysis of the rDNA sequence showed important mismatches of some published diagnostic PCR primers and high GC content of T. vivax rDNA. The evaluation of selected diagnostic PCR assays with specimens from cattle under natural T. vivax challenge showed that this high GC content interferes with the diagnostic accuracy of PCR, especially in cases of mixed infections with T. congolense. Adding betain to the PCR reaction mixture can enhance the amplification of T. vivax rDNA but decreases the sensitivity for T. congolense and Trypanozoon. The networks illustrated that Ethiopian T. vivax strains are considerably heterogeneous and two strains (one from tsetse-infested and one from tsetse-free area) are more related to the West African and South American strains than to the East African strains. The rDNA locus sequence of six Ethiopian T. vivax
Drancourt, Michel; Bollet, Claude; Carlioz, Antoine; Martelin, Rolland; Gayral, Jean-Pierre; Raoult, Didier
Some bacteria are difficult to identify with phenotypic identification schemes commonly used outside reference laboratories. 16S ribosomal DNA (rDNA)-based identification of bacteria potentially offers a useful alternative when phenotypic characterization methods fail. However, as yet, the usefulness of 16S rDNA sequence analysis in the identification of conventionally unidentifiable isolates has not been evaluated with a large collection of isolates. In this study, we evaluated the utility of 16S rDNA sequencing as a means to identify a collection of 177 such isolates obtained from environmental, veterinary, and clinical sources. For 159 isolates (89.8%) there was at least one sequence in GenBank that yielded a similarity score of ≥97%, and for 139 isolates (78.5%) there was at least one sequence in GenBank that yielded a similarity score of ≥99%. These similarity score values were used to defined identification at the genus and species levels, respectively. For isolates identified to the species level, conventional identification failed to produce accurate results because of inappropriate biochemical profile determination in 76 isolates (58.7%), Gram staining in 16 isolates (11.6%), oxidase and catalase activity determination in 5 isolates (3.6%) and growth requirement determination in 2 isolates (1.5%). Eighteen isolates (10.2%) remained unidentifiable by 16S rDNA sequence analysis but were probably prototype isolates of new species. These isolates originated mainly from environmental sources (P = 0.07). The 16S rDNA approach failed to identify Enterobacter and Pantoea isolates to the species level (P = 0.04; odds ratio = 0.32 [95% confidence interval, 0.10 to 1.14]). Elsewhere, the usefulness of 16S rDNA sequencing was compromised by the presence of 16S rDNA sequences with >1% undetermined positions in the databases. Unlike phenotypic identification, which can be modified by the variability of expression of characters, 16S rDNA sequencing provides
Yoon, Y; Sanchez, J A; Brun, C; Huberman, J A
New techniques for mapping mammalian DNA replication origins are needed. We have modified the existing nascent-strand size analysis technique (L. Vassilev and E.M. Johnson, Nucleic Acids Res. 17:7693-7705, 1989) to provide an independent means of studying replication initiation sites. We call the new method nascent-strand abundance analysis. We confirmed the validity of this method with replicating simian virus 40 DNA as a model. We then applied nascent-strand abundance and nascent-strand size analyses to mapping of initiation sites in human (HeLa) ribosomal DNA (rDNA), a region previously examined exclusively by two-dimensional gel electrophoresis methods (R.D. Little, T.H.K. Platt, and C.L. Schildkraut, Mol. Cell. Biol. 13:6600-6613, 1993). Our results partly confirm those obtained by two-dimensional gel electrophoresis techniques. Both studies suggest that replication initiates at relatively high frequency a few kilobase pairs upstream of the transcribed region and that many additional low-frequency initiation sites are distributed through most of the remainder of the ribosomal DNA repeat unit. PMID:7739533
Yagi, Kouhei; Pawełkowicz, Magdalena; Osipowski, Paweł; Siedlecka, Ewa; Przybecki, Zbigniew; Tagashira, Norikazu; Hoshi, Yoshikazu; Malepszy, Stefan; Pląder, Wojciech
Wild Cucumis species have been divided into Australian/Asian and African groups using morphological and phylogenetic characteristics, and new species have been described recently. No molecular cytogenetic information is available for most of these species. The crossability between 5 southern African Cucumis species (C. africanus, C. anguria, C. myriocarpus, C. zeyheri, and C. heptadactylus) has been reported; however, the evolutionary relationship among them is still unclear. Here, a molecular cytogenetic analysis using FISH with 5S and 45 S ribosomal DNA (rDNA) was used to investigate these Cucumis species based on sets of rDNA-bearing chromosomes (rch) types I, II and III. The molecular cytogenetic and phylogenetic results suggested that at least 2 steps of chromosomal rearrangements may have occurred during the evolution of tetraploid C. heptadactylus. In step 1, an additional 45 S rDNA site was observed in the chromosome (type III). In particular, C. myriocarpus had a variety of rch sets. Our results suggest that chromosomal rearrangements may have occurred in the 45 S rDNA sites. We propose that polyploid evolution occurred in step 2. This study provides insights into the chromosomal characteristics of African Cucumis species and contributes to the understanding of chromosomal evolution in this genus.
Nava, S; Szabó, M P J; Mangold, A J; Guglielmone, A A
The hosts, distribution, intraspecific genetic variation and phylogenetic position of Amblyomma parvum (Acari: Ixodidae) have recently been re-assessed. Data on this tick's hosts and distribution were obtained not only from existing literature but also from unpublished records. Sequences of the ticks' mitochondrial 16S ribosomal DNA (rDNA) were used to evaluate genetic variation among specimens of A. parvum from different localities in Argentina and Brazil, and to explore the phylogenetic relationships between this tick and other Amblyomma species. Although several species of domestic and wild mammal act as hosts for adult A. parvum, most collected adults of this species have come from cattle and goats. Caviid rodents of the subfamily Caviinae appear to be the hosts for the immature stages. So far, A. parvum has been detected in 12 Neotropical biogeographical provinces (Chaco, Cerrado, Eastern Central America, Venezuelan Coast, Pantanal, Parana Forest, Caatinga, Chiapas, Venezuelan Llanos, Monte, Western Panamanian Isthmus, and Roraima) but the Chaco province has provided significantly more specimens than any other (P<0.0001). The 16S rDNA sequences showed just 0.0%-1.1% divergence among the Argentinean A. parvum investigated and no more than 0.2% divergence among the Brazilian specimens. The observed divergence between the Argentinean and Brazilian specimens was, however, greater (3.0%-3.7%). Although there is now molecular and morphological evidence to indicate that A. parvum, A. pseudoparvum, A. auricularium and A. pseudoconcolor are members of a natural group, previous subgeneric classifications do not reflect this grouping. The subgeneric status of these tick species therefore needs to be re-evaluated. The 16S-rDNA-based evaluation of divergence indicates that the gene flow between Argentinean and Brazilian 'A. parvum' is very limited and that the Argentinean 'A. parvum' may be a different species to the Brazilian.
Nielsen, Christian F; Hickson, Ian D
PICH is an SNF2-family DNA translocase that appears to play a role specifically in mitosis. Characterization of PICH in human cells led to the initial discovery of "ultra-fine DNA bridges" (UFBs) that connect the 2 segregating DNA masses in the anaphase of mitosis. These bridge structures, which arise from specific regions of the genome, are a normal feature of anaphase but had escaped detection previously because they do not stain with commonly used DNA dyes. Nevertheless, UFBs are important for genome maintenance because defects in UFB resolution can lead to cytokinesis failure. We reported recently that PICH stimulates the unlinking (decatenation) of entangled DNA by Topoisomerase IIα (Topo IIα), and is important for the resolution of UFBs. We also demonstrated that PICH and Topo IIα co-localize at the rDNA (rDNA). In this Extra View article, we discuss the mitotic roles of PICH and explore further the role of PICH in the timely segregation of the rDNA locus.
Matyášek, Roman; Dobešová, Eva; Húska, Dalibor; Ježková, Ivana; Soltis, Pamela S; Soltis, Douglas E; Kovařík, Aleš
Uniparental silencing of 35S rRNA genes (rDNA), known as nucleolar dominance (ND), is common in interspecific hybrids. Allotetraploid Tragopogon mirus composed of Tragopogon dubius (d) and Tragopogon porrifolius (p) genomes shows highly variable ND. To examine the molecular basis of such variation, we studied the genetic and epigenetic features of rDNA homeologs in several lines derived from recently and independently formed natural populations. Inbred lines derived from T. mirus with a dominant d-rDNA homeolog transmitted this expression pattern over generations, which may explain why it is prevalent among natural populations. In contrast, lines derived from the p-rDNA dominant progenitor were meiotically unstable, frequently switching to co-dominance. Interpopulation crosses between progenitors displaying reciprocal ND resulted in d-rDNA dominance, indicating immediate suppression of p-homeologs in F1 hybrids. Original p-rDNA dominance was not restored in later generations, even in those segregants that inherited the corresponding parental rDNA genotype, thus indicating the generation of additional p-rDNA and d-rDNA epigenetic variants. Despite preserved intergenic spacer (IGS) structure, they showed altered cytosine methylation and chromatin condensation patterns, and a correlation between expression, hypomethylation of RNA Pol I promoters and chromatin decondensation was apparent. Reversion of such epigenetic variants occurred rarely, resulting in co-dominance maintained in individuals with distinct genotypes. Generally, interpopulation crosses may generate epialleles that are not present in natural populations, underlying epigenetic dynamics in young allopolyploids. We hypothesize that highly expressed variants with distinct IGS features may induce heritable epigenetic reprogramming of the partner rDNA arrays, harmonizing the expression of thousands of genes in allopolyploids.
Sun, Hengyi; Zang, Xiaonan; Liu, Yuantao; Cao, Xiaofei; Wu, Fei; Huang, Xiaoyun; Jiang, Minjie; Zhang, Xuecheng
Calcitonin participates in controlling homeostasis of calcium and phosphorus and plays an important role in bone metabolism. The aim of this study was to endow an industrial strain of Saccharomyces cerevisiae with the ability to express chimeric human/salmon calcitonin (hsCT) without the use of antibiotics. To do so, a homologous recombination plasmid pUC18-rDNA2-ura3-P pgk -5hsCT-rDNA1 was constructed, which contains two segments of ribosomal DNA of 1.1 kb (rDNA1) and 1.4 kb (rDNA2), to integrate the heterologous gene into host rDNA. A DNA fragment containing five copies of a chimeric human/salmon calcitonin gene (5hsCT) under the control of the promoter for phosphoglycerate kinase (P pgk ) was constructed to express 5hsCT in S. cerevisiae using ura3 as a selectable auxotrophic marker gene. After digestion by restriction endonuclease HpaI, a linear fragment, rDNA2-ura3-P pgk -5hsCT-rDNA1, was obtained and transformed into the △ura3 mutant of S. cerevisiae by the lithium acetate method. The ura3-P pgk -5hsCT sequence was introduced into the genome at rDNA sites by homologous recombination, and the recombinant strain YS-5hsCT was obtained. Southern blot analysis revealed that the 5hsCT had been integrated successfully into the genome of S. cerevisiae. The results of Western blot and ELISA confirmed that the 5hsCT protein had been expressed in the recombinant strain YS-5hsCT. The expression level reached 2.04 % of total proteins. S. cerevisiae YS-5hsCT decreased serum calcium in mice by oral administration and even 0.01 g lyophilized S. cerevisiae YS-5hsCT/kg decreased serum calcium by 0.498 mM. This work has produced a commercial yeast strain potentially useful for the treatment of osteoporosis.
Du, Xi-Hui; Zhao, Qi; Yang, Zhu L; Hansen, Karen; Taskin, Hatira; Büyükalaca, Saadet; Dewsbury, Damon; Moncalvo, Jean-Marc; Douhan, Greg W; Robert, Vincent A R G; Crous, Pedro W; Rehner, Stephen A; Rooney, Alejandro P; Sink, Stacy; O'Donnell, Kerry
Arguably more mycophiles hunt true morels (Morchella) during their brief fruiting season each spring in the northern hemisphere than any other wild edible fungus. Concerns about overharvesting by individual collectors and commercial enterprises make it essential that science-based management practices and conservation policies are developed to ensure the sustainability of commercial harvests and to protect and preserve morel species diversity. Therefore, the primary objectives of the present study were to: (i) investigate the utility of the ITS rDNA locus for identifying Morchella species, using phylogenetic species previously inferred from multilocus DNA sequence data as a reference; and (ii) clarify insufficiently identified sequences and determine whether the named sequences in GenBank were identified correctly. To this end, we generated 553 Morchella ITS rDNA sequences and downloaded 312 additional ones generated by other researchers from GenBank using emerencia and analyzed them phylogenetically. Three major findings emerged: (i) ITS rDNA sequences were useful in identifying 48/62 (77.4%) of the known phylospecies; however, they failed to identify 12 of the 22 species within the species-rich Elata Subclade and two closely related species in the Esculenta Clade; (ii) at least 66% of the named Morchella sequences in GenBank are misidentified; and (iii) ITS rDNA sequences of up to six putatively novel Morchella species were represented in GenBank. Recognizing the need for a dedicated Web-accessible reference database to facilitate the rapid identification of known and novel species, we constructed Morchella MLST (http://www.cbs.knaw.nl/morchella/), which can be queried with ITS rDNA sequences and those of the four other genes used in our prior multilocus molecular systematic studies of this charismatic genus.
Three stunt nematode species, Tylenchorhynchus leviterminalis, T. claytoni and Bitylenchus dubius were characterized with segments of small subunit 18S and large subunit 28S rDNA sequences and placed in molecular phylogenetic context with other taxa of Telotylechidae in GenBank. In 18S trees, the sp...
Sobol, Margaryta; Kordyum, Elizabeth; Medina, Francisco Javier
The nucleolus is an inner nuclear organelle originated from the activity of hundreds of rRNA genes, typically spanning several megabases. It morphologically reflects the functional events leading to ribosome biogenesis, from the transcription of rDNA through the processing of nascent pre-rRNA to the assembly of pre-ribosomes. A typical nucleolus consists of three major elements, namely fibrillar centers (FCs), the dense fibrillar component (DFC), and granular component (GC). The rate of ribosome biosynthesis and the subnucleolar structure are reliable monitors of the general level of cell metabolism and, consequently, of the rate of cellular growth, being influenced with many external factors, among which altered gravity could be included. Thus, we can hypothesize that the structural organization of the nucleolar subcomponents and the level, distribution and quantitative/qualitative characteristics of the nucleolar proteins would be changed under conditions of altered gravity. To confirm our hypothesis, we applied parallel procedures, such as cytochemistry, immunofluorescence, confocal laser microscopy, immunogold electron microscopy, monoand bi-dimensional electrophoresis and immunoblotting in root meristematic cells from two-day cress seedlings grown under slow horizontal clinorotation (2 rpm) and in stationary control. The complex model of the ultrastructural organization and functions of the nucleolus was created based on the location of rDNA and the nucleolar proteins fibrillarin, NhL90 and NhL68, these latter being cress nucleolin homologues. The principal stages of ribosome biogenesis, namely ribosomal gene activation, rDNA transcription and pre-rRNA processing were reflected in this model. Compared to the pattern shown in control ground gravity conditions, we found firstly a redistribution of both rDNA and nucleolar proteins in nucleolar subcomponents, induced by clinorotation. Under the conditions of altered gravity, nucleolar DNA concentrated
Hall, Val; Talbot, P. R.; Stubbs, S. L.; Duerden, B. I.
Amplified 16S ribosomal DNA (rDNA) restriction analysis (ARDRA), using enzymes HaeIII and HpaII, was applied to 176 fresh and 299 stored clinical isolates of putative Actinomyces spp. referred to the Anaerobe Reference Unit of the Public Health Laboratory Service for confirmation of identity. Results were compared with ARDRA results obtained previously for reference strains and with conventional phenotypic reactions. Identities of some strains were confirmed by analysis of partial 16S rDNA sequences. Of the 475 isolates, 331 (70%) were clearly assigned to recognized Actinomyces species, including 94 isolates assigned to six recently described species. A further 52 isolates in 12 ARDRA profiles were designated as apparently resembling recognized species, and 44 isolates, in 18 novel profiles, were confirmed as members of genera other than Actinomyces. The identities of 48 isolates in nine profiles remain uncertain, and they may represent novel species of Actinomyces. For the majority of species, phenotypic results, published reactions for the species, and ARDRA profiles concurred. However, of 113 stored isolates originally identified as A. meyeri or resembling A. meyeri by phenotypic tests, only 21 were confirmed as A. meyeri by ARDRA; 63 were reassigned as A. turicensis, 7 as other recognized species, and 22 as unidentified actinomycetes. Analyses of incidence and clinical associations of Actinomyces spp. add to the currently sparse knowledge of some recently described species. PMID:11574572
Patton, Toni G; Scupham, Alexandra J; Bearson, Shawn M D; Carlson, Steve A
The gastrointestinal (GI) tract microbiota is composed of complex communities. For all species examined thus far, culture and molecular analyses show that these communities are highly diverse and individuals harbor unique consortia. The objective of the current work was to examine inter-individual diversity of cattle fecal microbiota and determine whether Salmonella shedding status correlated with community richness or evenness parameters. Using a ribosomal gene array-based approach, oligonucleotide fingerprinting of ribosomal genes (OFRG), we analyzed 1440 16S genes from 19 fecal samples obtained from a cattle herd with a history of salmonellosis. Identified bacteria belonged to the phyla Firmicutes (53%), Bacteroidetes (17%), and Proteobacteria (17%). Sequence analysis of 16S rDNA gene clones revealed that Spirochaetes and Verrucomicrobia were also present in the feces. The majority of Firmicutes present in the feces belonged to the order Clostridiales, which was verified via dot blot analysis. beta-Proteobacteria represented 1.5% of the bacterial community as determined by real-time PCR. Statistical analysis of the 16S libraries from the 19 animals indicated very high levels of species richness and evenness, such that individual libraries represented unique populations. Finally, this study did not identify species that prevented Salmonella colonization or resulted from Salmonella colonization.
Oling, David; Masoom, Rehan; Kvint, Kristian
Ubp3 is a conserved ubiquitin protease that acts as an antisilencing factor in MAT and telomeric regions. Here we show that ubp3∆ mutants also display increased silencing in ribosomal DNA (rDNA). Consistent with this, RNA polymerase II occupancy is lower in cells lacking Ubp3 than in wild-type cells in all heterochromatic regions. Moreover, in a ubp3∆ mutant, unequal recombination in rDNA is highly suppressed. We present genetic evidence that this effect on rDNA recombination, but not silencing, is entirely dependent on the silencing factor Sir2. Further, ubp3∆ sir2∆ mutants age prematurely at the same rate as sir2∆ mutants. Thus our data suggest that recombination negatively influences replicative life span more so than silencing. However, in ubp3∆ mutants, recombination is not a prerequisite for aging, since cells lacking Ubp3 have a shorter life span than isogenic wild-type cells. We discuss the data in view of different models on how silencing and unequal recombination affect replicative life span and the role of Ubp3 in these processes.
Pang, Jialun; Wu, Yong; Li, Zhuo; Hu, Zhiqing; Wang, Xiaolin; Hu, Xuyun; Wang, Xiaoyan; Liu, Xionghao; Zhou, Miaojin; Liu, Bo; Wang, Yanchi; Feng, Mai; Liang, Desheng
Hemophilia A (HA) is a monogenic disease due to lack of the clotting factor VIII (FVIII). This deficiency may lead to spontaneous joint hemorrhages or life-threatening bleeding but there is no cure for HA until very recently. In this study, we derived induced pluripotent stem cells (iPSCs) from patients with severe HA and used transcription activator-like effector nickases (TALENickases) to target the factor VIII gene (F8) at the multicopy ribosomal DNA (rDNA) locus in HA-iPSCs, aiming to rescue the shortage of FVIII protein. The results revealed that more than one copy of the exogenous F8 could be integrated into the rDNA locus. Importantly, we detected exogenous F8 mRNA and FVIII protein in targeted HA-iPSCs. After they were differentiated into endothelial cells (ECs), the exogenous FVIII protein was still detectable. Thus, it is showed that the multicopy rDNA locus could be utilized as an effective target site in patient-derived iPSCs for gene therapy. This strategy provides a novel iPSCs-based therapeutic option for HA and other monogenic diseases.
Sasaki, Y; Yamamoto, K; Kojima, A; Tetsuka, Y; Norimatsu, M; Tamura, Y
Clostridium chauvoei causes blackleg, which is difficult to distinguish from the causative clostridia of malignant edema. Therefore, a single-step PCR system was developed for specific detection of C. chauvoei DNA using primers derived from the 16S-23S rDNA spacer region and partial 23S rDNA sequences. The specificity of the single-step PCR system was demonstrated by testing 37 strains of clostridia and 3 strains of other genera. A 509 bp PCR product, which is a C. choauvoei-specific PCR product, could be amplified from all of the C. chauvoei strains tested, but not from the other strains. Moreover, this single-step PCR system specifically detected C. chauvoei DNA in samples of muscle from mice 24 hr after inoculation with 100 spores of C. chauvoei, and in clinical materials from a cow affected with blackleg. These results suggest that our single-step PCR system may be useful for direct detection of C. chauvoei in culture and in clinical materials from animals affected with blackleg.
Background 45S rDNA sites are the most widely documented chromosomal regions in eukaryotes. The analysis of the distribution of these sites along the chromosome in several genera has suggested some bias in their distribution. In order to evaluate if these loci are in fact non-randomly distributed and what is the influence of some chromosomal and karyotypic features on the distribution of these sites, a database was built with the position and number of 45S rDNA sites obtained by FISH together with other karyotypic data from 846 plant species. Results In angiosperms the most frequent numbers of sites per diploid karyotype were two and four, suggesting that in spite of the wide dispersion capacity of these sequences the number of rDNA sites tends to be restricted. The sites showed a preferential distribution on the short arms, mainly in the terminal regions. Curiously, these sites were frequently found on the short arms of acrocentric chromosomes where they usually occupy the whole arm. The trend to occupy the terminal region is especially evident in holokinetic chromosomes, where all of them were terminally located. In polyploids there is a trend towards reduction in the number of sites per monoploid complement. In gymnosperms, however, the distribution of rDNA sites varied strongly among the sampled families. Conclusions The location of 45S rDNA sites do not vary randomly, occurring preferentially on the short arm and in the terminal region of chromosomes in angiosperms. The meaning of this preferential location is not known, but some hypotheses are considered and the observed trends are discussed. PMID:23181612
Xu, Chao; Wang, Chunsheng; Sun, Xinyao; Zhang, Rong; Gleason, Mark L.; Eiji, Tanaka; Sun, Guangyu
Botryosphaeria dothidea is a widespread and economically important pathogen on various fruit trees, and it often causes die-back and canker on limbs and fruit rot. In characterizing intraspecies genetic variation within this fungus, group I introns, rich in rDNA of fungi, may provide a productive region for exploration. In this research, we analysed complete small subunit (SSU) ribosomal DNA (rDNA) sequences of 37 B. dothidea strains, and found four insertions, designated Bdo.S943, Bdo.S1199-A, Bdo.S1199-B and Bdo.S1506, at three positions. Sequence analysis and structure prediction revealed that both Bdo.S943 and Bdo.S1506 belonged to subgroup IC1 of group I introns, whereas Bdo.S1199-A and Bdo.S1199-B corresponded to group IE introns. Moreover, Bdo.S1199-A was found to host an open reading frame (ORF) for encoding the homing endonuclease (HE), whereas Bdo.S1199-B, an evolutionary descendant of Bdo.S1199-A, included a degenerate HE. The above four introns were novel, and were the first group I introns observed and characterized in this species. Differential distribution of these introns revealed that all strains could be separated into four genotypes. Genotype III (no intron) and genotype IV (Bdo.S1199-B) were each found in only one strain, whereas genotype I (Bdo.S1199-A) and genotype II (Bdo.S943 and Bdo.S1506) occurred in 95% of the strains. There is a correlation between B. dothidea genotypes and hosts or geographic locations. Thus, these newly discovered group I introns can help to advance understanding of genetic differentiation within B. dothidea. PMID:23844098
Xu, Chao; Wang, Chunsheng; Sun, Xinyao; Zhang, Rong; Gleason, Mark L; Eiji, Tanaka; Sun, Guangyu
Botryosphaeria dothidea is a widespread and economically important pathogen on various fruit trees, and it often causes die-back and canker on limbs and fruit rot. In characterizing intraspecies genetic variation within this fungus, group I introns, rich in rDNA of fungi, may provide a productive region for exploration. In this research, we analysed complete small subunit (SSU) ribosomal DNA (rDNA) sequences of 37 B. dothidea strains, and found four insertions, designated Bdo.S943, Bdo.S1199-A, Bdo.S1199-B and Bdo.S1506, at three positions. Sequence analysis and structure prediction revealed that both Bdo.S943 and Bdo.S1506 belonged to subgroup IC1 of group I introns, whereas Bdo.S1199-A and Bdo.S1199-B corresponded to group IE introns. Moreover, Bdo.S1199-A was found to host an open reading frame (ORF) for encoding the homing endonuclease (HE), whereas Bdo.S1199-B, an evolutionary descendant of Bdo.S1199-A, included a degenerate HE. The above four introns were novel, and were the first group I introns observed and characterized in this species. Differential distribution of these introns revealed that all strains could be separated into four genotypes. Genotype III (no intron) and genotype IV (Bdo.S1199-B) were each found in only one strain, whereas genotype I (Bdo.S1199-A) and genotype II (Bdo.S943 and Bdo.S1506) occurred in 95% of the strains. There is a correlation between B. dothidea genotypes and hosts or geographic locations. Thus, these newly discovered group I introns can help to advance understanding of genetic differentiation within B. dothidea.
Zhao, Ya-E; Hu, Li; Ma, Jun-Xian
Classification of Demodex mites has long depended on hosts and morphological characteristics. However, the fact that two species coexist in the same host and phenotype is easily influenced by environment causes difficulty and indeterminacy in traditional classification. Genotype, which directly reflects the molecular structure characteristics, is relatively stable. In this study, species identification of four phenotypes of human Demodex mites was conducted. Mites were morphologically classified into four phenotypes: long- and short-bodied Demodex folliculorum with finger-like terminus and Demodex brevis with finger- or cone-like terminus. The mitochondrial 16S ribosomal DNA (rDNA) fragment of individual mite was amplified, cloned, sequenced, and aligned. Sequence divergences, genetic distances, transition/transversion rates, and phylogenetic trees were analyzed. The results demonstrated that the 16S rDNA sequence of three phenotypes with finger-like terminus was 337 bp, and that of phenotype with cone-like terminus was 342 bp. The divergences, genetic distances, and transition/transversion rates among the three phenotypes with finger-like terminus were 0.0-2.7%, 0.000-0.029, and 5.0-7/0 (5/1-7/0), respectively, indicating an intraspecific variation. Yet, those between these three phenotypes and the one with cone-like terminus were 21.6-22.8%, 2.510-2.589, and 0.47-0.59 (22/47-27/46), respectively, suggesting an interspecific variation. The five phylogenetic trees showed that the three phenotypes with finger-like terminus clustered into one branch, while the phenotype with cone-like terminus clustered into another. In conclusion, terminus is a major morphological characteristic for the identification of human Demodex species. The three phenotypes with finger-like terminus belong to D. folliculorum, while the phenotype with cone-like terminus belongs to D. brevis. Molecular identification can verify and replenish morphological identification.
Machida, Ryuji J.; Kweskin, Matthew; Knowlton, Nancy
Background Assessment of the biodiversity of communities of small organisms is most readily done using PCR-based analysis of environmental samples consisting of mixtures of individuals. Known as metagenetics, this approach has transformed understanding of microbial communities and is beginning to be applied to metazoans as well. Unlike microbial studies, where analysis of the 16S ribosomal DNA sequence is standard, the best gene for metazoan metagenetics is less clear. In this study we designed a set of PCR primers for the mitochondrial 12S ribosomal DNA sequence based on 64 complete mitochondrial genomes and then tested their efficacy. Methodology/Principal Findings A total of the 64 complete mitochondrial genome sequences representing all metazoan classes available in GenBank were downloaded using the NCBI Taxonomy Browser. Alignment of sequences was performed for the excised mitochondrial 12S ribosomal DNA sequences, and conserved regions were identified for all 64 mitochondrial genomes. These regions were used to design a primer pair that flanks a more variable region in the gene. Then all of the complete metazoan mitochondrial genomes available in NCBI's Organelle Genome Resources database were used to determine the percentage of taxa that would likely be amplified using these primers. Results suggest that these primers will amplify target sequences for many metazoans. Conclusions/Significance Newly designed 12S ribosomal DNA primers have considerable potential for metazoan metagenetic analysis because of their ability to amplify sequences from many metazoans. PMID:22536450
Vitturi, Roberto; Colomba, Mariastella; Volpe, Nicola; Lannino, Antonella; Zunino, Mario
In scarab beetle species of the genus Pentodon, the lack of analysis of sex chromosomes in females along with the poor characterization of sex chromosomes in the males, prevented all previous investigations from conclusively stating sex determination system. In this study, somatic chromosomes from females and spermatogonial chromosomes from males of Pentodon bidens punctatum (Coleoptera: Scarabaeoidea: Scarabaeidae) from Sicily have been analyzed using non-differential Giemsa staining. Two modal numbers of chromosomes were obtained: 2n = 20 and 19 in females and males, respectively. This finding along with other karyological characteristics such as the occurrence of one unpaired, heterotypic chromosome at metaphase-I and two types of metaphase-II spreads in spermatocytes demonstrate that a XO male/XX female sex determining mechanism - quite unusual among Scarabaeoidea - operates in the species investigated here. Spermatocyte chromosomes have also been examined after a number of banding techniques and fluorescent in situ hybridization with ribosomal sequences as a probe (rDNA FISH). The results obtained showed that silver and CMA(3) staining were inadequate to localize the chromosome sites of nucleolus organizer regions (NORs) due to the over-all stainability of both constitutive heterochromatin and heterochromatin associated to the NORs. This suggests that heterochromatic DNA of P. b. punctatum is peculiar as compared with other types of heterochromatin studied so far in other invertebrate taxa. By rDNA FISH major ribosomal genes were mapped on the X chromosome.
Vizoso, Miguel; Vierna, Joaquín; González-Tizón, Ana M; Martínez-Lage, Andrés
Several reports on the characterization of 5S ribosomal DNA (5S rDNA) in various animal groups have been published to date, but there is a lack of studies analyzing this gene family in a much broader context. Here, we have studied 5S rDNA variation in several molluskan species, including bivalves, gastropods, and cephalopods. The degree of conservation of transcriptional regulatory regions was analyzed in these lineages, revealing a conserved TATA-like box in the upstream region. The evolution of the 120 bp coding region (5S) was also studied, suggesting the occurrence of paralogue groups in razor clams, clams, and cockles. In addition, 5S rDNA sequences from 11 species and 7 genus of Mytilidae Rafinesque, 1815 mussels were sampled and studied in detail. Four different 5S rDNA types, based on the nontranscribed spacer region were identified. The phylogenetic analyses performed within each type showed a between-species gene clustering pattern, suggesting ancestral polymorphism. Moreover, some putative pseudogenized 5S copies were also identified. Our report, together with previous studies that found high degree of intragenomic divergence in bivalve species, suggests that birth-and-death evolution may be the main force driving the evolution of 5S rDNA in these animals, even at the genus level.
Huan, Pin; Zhang, Xiaojun; Li, Fuhua; Zhao, Cui; Zhang, Chengsong; Xiang, Jianhai
Chinese shrimp ( Fenneropenaeus chinensis) is an economically important aquaculture species in China. However, cytogenetic and genomic data is limited in the organism partly because the chromosomes are difficult to isolate and analyze. In this study, fluorescence in-situ hybridization (FISH) was used to identify the chromosomes of F. chinensis. The 5S ribosomal RNA gene (rDNA) of F. chinensis was isolated, cloned and then used as a hybridization probe. The results show that the 5S rDNA was located on one pair of homologous chromosomes in F. chinensis. In addition, triploid shrimp were used to evaluate the feasibility of chromosome identification using FISH and to validate the method. It was confirmed that 5S rDNA can be used as a chromosome-specific probe for chromosome identification in F. chinensis. The successful application of FISH in F. chinensis shows that chromosome-specific probes can be developed and this finding will facilitate further research on the chromosomes of penaeid shrimps.
Muchová, Veronika; Amiard, Simon; Mozgová, Iva; Dvořáčková, Martina; Gallego, Maria E; White, Charles; Fajkus, Jiří
Arabidopsis thaliana mutants in FAS1 and FAS2 subunits of chromatin assembly factor 1 (CAF1) show progressive loss of 45S rDNA copies and telomeres. We hypothesized that homology-dependent DNA damage repair (HDR) may contribute to the loss of these repeats in fas mutants. To test this, we generated double mutants by crossing fas mutants with knock-out mutants in RAD51B, one of the Rad51 paralogs of A. thaliana. Our results show that the absence of RAD51B decreases the rate of rDNA loss, confirming the implication of RAD51B-dependent recombination in rDNA loss in the CAF1 mutants. Interestingly, this effect is not observed for telomeric repeat loss, which thus differs from that acting in rDNA loss. Involvement of DNA damage repair in rDNA dynamics in fas mutants is further supported by accumulation of double-stranded breaks (measured as γ-H2AX foci) in 45S rDNA. Occurrence of the foci is not specific for S-phase, and is ATM-independent. While the foci in fas mutants occur both in the transcribed (intranucleolar) and non-transcribed (nucleoplasmic) fraction of rDNA, double fas rad51b mutants show a specific increase in the number of the intranucleolar foci. These results suggest that the repair of double-stranded breaks present in the transcribed rDNA region is RAD51B dependent and that this contributes to rDNA repeat loss in fas mutants, presumably via the single-stranded annealing recombination pathway. Our results also highlight the importance of proper chromatin assembly in the maintenance of genome stability.
Blok, V. C.; Malloch, G.; Harrower, B.; Phillips, M. S.; Vrain, T. C.
The relationships among a number of populations of Globodera pallida from Britian, the Netherlands, Germany, Switzerland, and South America were examined using PCR amplification of the ribosomal cistron between the 18S and 28S genes that include the two intergenic spacer regions (ITS1 and ITS2) and the 5.8S gene. Amplifications produced a similar-sized product of 1150 bp from all populations. Digestion of the amplified fragment with a number of restriction enzymes showed differences among the populations. The restriction enzyme RsaI distinguished the most populations. The RFLP patterns revealed by this enzyme were complex and could have arisen from heterogeneity between individuals within populations and from differences between the repeats of an individual. Sequence analysis from six of the populations, together with RFLP analysis of PCR products, shows that there is intraspecific variation in the rDNA of G. pallida. PMID:19274220
Iwanowicz, L.R.; Iwanowicz, D.D.; Pote, L.M.; Blazer, V.S.; Schill, W.B.
Henneguya gurlei was isolated from Ameiurus nebulosus captured in North Carolina and redescribed using critical morphological features and 18S small-subunit ribosomal RNA (SSU rDNA) gene sequence. Plasmodia are white, spherical, or subspherical, occur in clusters, measure up to 1.8 mm in length, and are located on the dorsal, pectoral, and anal fins. Histologically, plasmodia are located in the dermis and subdermally, and the larger cysts disrupt the melanocyte pigment layer. The spore body is lanceolate, 18.2 ?? 0.3 ??m (range 15.7-20.3) in length, and 5.4 ?? 0.1 ??m (range 3.8-6.1) in width in valvular view. The caudal appendages are 41.1 ?? 1.1 ??m (range 34.0-49.7) in length. Polar capsules are pyriform and of unequal size. The longer polar capsule measures 6.2 ?? 0.1 ??m (range 5.48-7.06), while the shorter is 5.7 ?? 0.1 ??m (range 4.8-6.4) in length. Polar capsule width is 1.2 ?? 0.03 ??m (range 1.0-1.54). The total length of the spore is 60.9 ?? 1.2 ??m (range 48.7-68.5). Morphologically, this species is similar to other species of Henneguya that are known to infect ictalurids. Based on SSU rDNA sequences, this species is most closely related to H. exilis and H. ictaluri, which infect Ictalurus punctatus. ?? American Society of Parasitologists 2008.
Long, Hong; Chen, Chunli; Wang, Bing; Feng, Yanni
The expression of rDNA in hybrids inherited from only one progenitor refers to nucleolar dominance. The molecular basis for choosing which genes to silence remains unclear. We report genetic imbalance induced by distant hybridization correlates with formation of rDNA genes (NORs) in the hybrids between Raphanus sativus L. and Brassica alboglabra Bailey. Moreover, increased CCGG methylation of rDNA in F1 hybrids is concomitant with Raphanus-derived rDNA gene silencing and rDNA transcriptional inactivity revealed by nucleolar configuration restriction. Newly formed rDNA gene locus occurred through chromosomal in F1 hybrids via chromosomal imbalance. NORs are gained de novo, lost, and/or transposed in the new genome. Inhibition of methyltransferases leads to changes in nucleolar architecture, implicating a key role of methylation in control of nucleolar dominance and vital nucleolar configuration transition. Our findings suggest that gene imbalance and methylation-related chromatin restructuring is important for rDNA gene silencing that may be crucial for synthesis of specific proteins.
Budaeva, Nataliya; Schepetov, Dmitry; Zanol, Joana; Neretina, Tatiana; Willassen, Endre
Onuphid polychaetes are tubicolous marine worms commonly reported worldwide from intertidal areas to hadal depths. They often dominate in benthic communities and have economic importance in aquaculture and recreational fishing. Here we report the phylogeny of the family Onuphidae based on the combined analyses of nuclear (18S rDNA) and mitochondrial (16S rDNA) genes. Results of Bayesian and Maximum Likelihood analyses supported the monophyly of Onuphidae and its traditional subdivision into two monophyletic subfamilies: Onuphinae and Hyalinoeciinae. Ten of 22 recognized genera were monophyletic with strong node support; four more genera included in this study were either monotypic or represented by a single species. None of the genera appeared para- or polyphyletic and this indicates a strong congruence between the traditional morphology-based systematics of the family and the newly obtained molecular-based phylogenetic reconstructions. Intergeneric relationships within Hyalinoeciinae were not resolved. Two strongly supported monophyletic groups of genera were recovered within Onuphinae: ((Onuphis, Aponuphis), Diopatra, Paradiopatra) and (Hirsutonuphis, (Paxtonia, (Kinbergonuphis, Mooreonuphis))). A previously accepted hypothesis on the subdivision of Onuphinae into the Onuphis group of genera and the Diopatra group of genera was largely rejected.
El-Sherry, Shiem; Ogedengbe, Mosun E; Hafeez, Mian A; Barta, John R
Multiple 18S rDNA sequences were obtained from two single-oocyst-derived lines of each of Eimeria meleagrimitis and Eimeria adenoeides. After analysing the 15 new 18S rDNA sequences from two lines of E. meleagrimitis and 17 new sequences from two lines of E. adenoeides, there were clear indications that divergent, paralogous 18S rDNA copies existed within the nuclear genome of E. meleagrimitis. In contrast, mitochondrial cytochrome c oxidase subunit I (COI) partial sequences from all lines of a particular Eimeria sp. were identical and, in phylogenetic analyses, COI sequences clustered unambiguously in monophyletic and highly-supported clades specific to individual Eimeria sp. Phylogenetic analysis of the new 18S rDNA sequences from E. meleagrimitis showed that they formed two distinct clades: Type A with four new sequences; and Type B with nine new sequences; both Types A and B sequences were obtained from each of the single-oocyst-derived lines of E. meleagrimitis. Together these rDNA types formed a well-supported E. meleagrimitis clade. Types A and B 18S rDNA sequences from E. meleagrimitis had a mean sequence identity of only 97.4% whereas mean sequence identity within types was 99.1-99.3%. The observed intraspecific sequence divergence among E. meleagrimitis 18S rDNA sequence types was even higher (approximately 2.6%) than the interspecific sequence divergence present between some well-recognized species such as Eimeria tenella and Eimeria necatrix (1.1%). Our observations suggest that, unlike COI sequences, 18S rDNA sequences are not reliable molecular markers to be used alone for species identification with coccidia, although 18S rDNA sequences have clear utility for phylogenetic reconstruction of apicomplexan parasites at the genus and higher taxonomic ranks.
We tested a method of estimating the activity of detectable individual bacterial and archaeal OTUs within a community by calculating ratios of absolute 16S rRNA to rDNA copy numbers. We investigated phylogenetically coherent patterns of activity among soil prokaryotes in non-growing soil communitie...
Harris, P D; Cable, J; Tinsley, R C; Lazarus, C M
A method is presented for the isolation and analysis of hamuli, marginal hooks, and bars from individual gyrodactylid monogeneans using scanning electron microscopy (SEM), while simultaneously processing parasites for rDNA analysis using the polymerase chain reaction (PCR). The haptors of ethanol-fixed gyrodactylids were protease digested to liberate hooks for SEM, whereas DNA extracted from the bodies was used for PCR. The method resulted in hooks and hamuli being prepared from more than 90% of Gyrodactylus turnbulli individuals, a significant improvement on previously published digestion-based SEM techniques. PCR on the same parasites was less successful, but sequence data were obtained from 50% of individuals. Amplification of rDNA internal-transcribed spacer regions from individual worms used for SEM gave PCR products consistent with those predicted from our previous sequence analysis. This method allows the correlation of morphology and DNA sequence from the same individual and can be applied to ethanol-fixed material, such as field collected and museum specimens.
Liu, Zhan-Lin; Zhang, Daming; Wang, Xiao-Quan; Ma, Xiao-Fei; Wang, Xiao-Ru
Patterns of intragenomic and interspecific variation of 5S rDNA in Pinus (Pinaceae) were studied by cloning and sequencing multiple 5S rDNA repeats from individual trees. Five pines, from both subgenera, Pinus and Strobus, were selected. The 5S rDNA repeat in pines has a conserved 120-base pair (bp) transcribed region and an intergenic spacer region of variable length (382-608 bp). The evolutionary rate in the spacer region is three- to sevenfold higher than in the genic region. We found substantial sequence divergence between the two subgenera. Intragenomic sequence heterogeneity was high for all species, and more than 86% of the clones within each individual were unique. The 5S gene tree revealed that different 5S repeats within individuals are polyphyletic, indicating that their ancestral divergence preceded the speciation events. The degrees of interspecific and intragenomic divergence among diploxylon pines are similar. The observed sequence patterns suggest that concerted evolution has been acting after the diversification of the two subgenera but very weak after the speciation of the four diploxylon pines. Sequence patterns in P. densata are consistent with hybrid origin. It had higher intragenomic diversity and maintained polymorphic copies of the parental types in addition to new and recombinant types unique to the hybrid.
Castro, Sergio I.; Hleap, Jose S.; Cárdenas, Heiber; Blouin, Christian
ABSTRACT The 5S rDNA gene is a non-coding RNA that can be found in 2 copies (type I and type II) in bony and cartilaginous fish. Previous studies have pointed out that type II gene is a paralog derived from type I. We analyzed the molecular organization of 5S rDNA type II in elasmobranchs. Although the structure of the 5S rDNA is supposed to be highly conserved, our results show that the secondary structure in this group possesses some variability and is different than the consensus secondary structure. One of these differences in Selachii is an internal loop at nucleotides 7 and 112. These mutations observed in the transcribed region suggest an independent origin of the gene among Batoids and Selachii. All promoters were highly conserved with the exception of BoxA, possibly due to its affinity to polymerase III. This latter enzyme recognizes a dT4 sequence as stop signal, however in Rajiformes this signal was doubled in length to dT8. This could be an adaptation toward a higher efficiency in the termination process. Our results suggest that there is no TATA box in elasmobranchs in the NTS region. We also provide some evidence suggesting that the complexity of the microsatellites present in the NTS region play an important role in the 5S rRNA gene since it is significantly correlated with the length of the NTS. PMID:26488198
Foronda, P; Casanova, J C; Martinez, E; Valladares, B; Feliu, C
The 18S rDNA gene of adult worms of Taenia parva found in Genetta genetta in the Iberian Peninsula and larval stages of T. pisiformis from the wild rabbit (Oryctolagus cuniculus) in Tenerife (Canary Islands) were amplified and sequenced. The sequences of the 18S rDNA gene of T. parva (1768 bp) and T. pisiformis (1760 bp) are reported for the first time (GenBank accession nos. AJ555167-AJ555168 and AJ555169-AJ555170, respectively). In 168 alignment positions microsatellites in the 18S rDNA of both taxa were detected for the first time (TGC in T. parva and TGCT in T. pisiformis) and differences in their sequences with different repetition numbers were observed. The use of nucleotide sequences of this gene in the resolution of systematic problems in cestodes is discussed with reference to the systematic status of Taenia spp. and mainly in human taeniids such as T. solium, T. saginata, and Asian human isolates of Taenia.
Nielsen, H; Simon, E M; Engberg, J
We have previously argued from phylogenetic sequence data that the group I intron in the rRNA genes of Tetrahymena was acquired by different Tetrahymena species at different times during evolution. We have now approached the question of intron mobility experimentally by crossing intron+ and intron- strains looking for a strong polarity in the inheritance of the intron (intron homing). Based on the genetic analysis we find that the intron in T. pigmentosa is inherited as a neutral character and that intron+ and intron- alleles segregate in a Mendelian fashion with no sign of intron homing. In an analysis of vegetatively growing cells containing intron+ and intron- rDNA, initially in the same macronucleus, we similarly find no evidence of intron homing. During the course of this work, we observed to our surprise that progeny clones from some crosses contained three types of rDNA. One possible explanation is that T. pigmentosa has two rdn loci in contrast to the single locus found in T. thermophila. Some of the progeny clones from the genetic analysis were expanded for several hundred generations, and allelic assortment of the rDNA was demonstrated by subcloning analysis.
Kaplan, D T; Thomas, W K; Frisse, L M; Sarah, J L; Stanton, J M; Speijer, P R; Marin, D H; Opperman, C H
The nucleic acid sequences of rDNA ITS1 and the rDNA D2/D3 expansion segment were compared for 57 burrowing nematode isolates collected from Australia, Cameroon, Central America, Cuba, Dominican Republic, Florida, Guadeloupe, Hawaii, Nigeria, Honduras, Indonesia, Ivory Coast, Puerto Rico, South Africa, and Uganda. Of the 57 isolates, 55 were morphologically similar to Radopholus similis and seven were citrus-parasitic. The nucleic acid sequences for PCR-amplified ITS1 and for the D2/D3 expansion segment of the 28S rDNA gene were each identical for all putative R. similis. Sequence divergence for both the ITS1 and the D2/D3 was concordant with morphological differences that distinguish R. similis from other burrowing nematode species. This result substantiates previous observations that the R. similis genome is highly conserved across geographic regions. Autapomorphies that would delimit phylogenetic lineages of non-citrus-parasitic R. similis from those that parasitize citrus were not observed. The data presented herein support the concept that R. similis is comprised of two pathotypes-one that parasitizes citrus and one that does not.
Kuznetsova, Valentina G.; Khabiev, Gadzhimurad N.; Anokhin, Boris A.
Abstract Myrmeleontidae, commonly known as “antlions”, are the most diverse family of the insect order Neuroptera, with over 1700 described species (in 191 genera) of which 37 species (in 21 genera) have so far been studied in respect to standard karyotypes. In the present paper we provide first data on the occurrence of the “insect-type” telomeric repeat (TTAGG)n and location of 18S rDNA clusters in the antlion karyotypes studied using fluorescence in situ hybridization (FISH). We show that males of Palpares libelluloides (Linnaeus, 1764) (Palparinae), Acanthaclisis occitanica (Villers, 1789) (Acanthaclisinae) and Distoleon tetragrammicus (Fabricius, 1798) (Nemoleontinae) have rDNA clusters on a large bivalent, two last species having an additional rDNA cluster on one of the sex chromosomes, most probably the X. (TTAGG)n - containing telomeres are clearly characteristic of Palpares libelluloides and Acanthaclisis occitanica; the presence of this telomeric motif in Distoleon tetragrammicus is questionable. In addition, we detected the presence of the (TTAGG)n telomeric repeat in Libelloides macaronius (Scopoli, 1763) from the family Ascalaphidae (owlflies), a sister group to the Myrmeleontidae. We presume that the “insect” motif (TTAGG)n was present in a common ancestor of the families Ascalaphidae and Myrmeleontidae within the neuropteran suborder Myrmeleontiformia. PMID:28123685
Laila, Rawnak; Robin, Arif Hasan Khan; Yang, Kiwoung; Choi, Gyung Ja; Park, Jong-In; Nou, Ill-Sup
Clubroot is a soil-borne disease caused by the protist Plasmodiophora brassicae (P. brassicae). It is one of the most economically important diseases of Brassica rapa and other cruciferous crops as it can cause remarkable yield reductions. Understanding P. brassicae genetics, and developing efficient molecular markers, is essential for effective detection of harmful races of this pathogen. Samples from 11 Korean field populations of P. brassicae (geographic isolates), collected from nine different locations in South Korea, were used in this study. Genomic DNA was extracted from the clubroot-infected samples to sequence the ribosomal DNA. Primers and probes for P. brassicae were designed using a ribosomal DNA gene sequence from a Japanese strain available in GenBank (accession number AB526843; isolate NGY). The nuclear ribosomal DNA (rDNA) sequence of P. brassicae, comprising 6932 base pairs (bp), was cloned and sequenced and found to include the small subunits (SSUs) and a large subunit (LSU), internal transcribed spacers (ITS1 and ITS2), and a 5.8s. Sequence variation was observed in both the SSU and LSU. Four markers showed useful differences in high-resolution melting analysis to identify nucleotide polymorphisms including single- nucleotide polymorphisms (SNPs), oligonucleotide polymorphisms, and insertions/deletions (InDels). A combination of three markers was able to distinguish the geographical isolates into two groups.
Laila, Rawnak; Robin, Arif Hasan Khan; Yang, Kiwoung; Choi, Gyung Ja; Park, Jong-In; Nou, Ill-Sup
Clubroot is a soil-borne disease caused by the protist Plasmodiophora brassicae (P. brassicae). It is one of the most economically important diseases of Brassica rapa and other cruciferous crops as it can cause remarkable yield reductions. Understanding P. brassicae genetics, and developing efficient molecular markers, is essential for effective detection of harmful races of this pathogen. Samples from 11 Korean field populations of P. brassicae (geographic isolates), collected from nine different locations in South Korea, were used in this study. Genomic DNA was extracted from the clubroot-infected samples to sequence the ribosomal DNA. Primers and probes for P. brassicae were designed using a ribosomal DNA gene sequence from a Japanese strain available in GenBank (accession number AB526843; isolate NGY). The nuclear ribosomal DNA (rDNA) sequence of P. brassicae, comprising 6932 base pairs (bp), was cloned and sequenced and found to include the small subunits (SSUs) and a large subunit (LSU), internal transcribed spacers (ITS1 and ITS2), and a 5.8s. Sequence variation was observed in both the SSU and LSU. Four markers showed useful differences in high-resolution melting analysis to identify nucleotide polymorphisms including single- nucleotide polymorphisms (SNPs), oligonucleotide polymorphisms, and insertions/deletions (InDels). A combination of three markers was able to distinguish the geographical isolates into two groups. PMID:28054984
Characterization of the Dominant and Rare Members of a Young Hawaiian Soil Bacterial Community with Small-Subunit Ribosomal DNA Amplified from DNA Fractionated on the Basis of Its Guanine and Cytosine Composition
Nüsslein, Klaus; Tiedje, James M.
The small-subunit ribosomal DNA (rDNA) diversity was found to be very high in a Hawaiian soil community that might be expected to have lower diversity than the communities in continental soils because the Hawaiian soil is geographically isolated and only 200 years old, is subjected to a constant climate, and harbors low plant diversity. Since an underlying community structure could not be revealed by analyzing the total eubacterial rDNA, we first fractionated the DNA on the basis of guanine-plus-cytosine (G+C) content by using bis-benzimidazole and equilibrium centrifugation and then analyzed the bacterial rDNA amplified from a fraction with a high biomass (63% G+C fraction) and a fraction with a low biomass (35% G+C fraction). The rDNA clone libraries were screened by amplified rDNA restriction analysis to determine phylotype distribution. The dominant biomass reflected by the 63% G+C fraction contained several dominant phylotypes, while the community members that were less successful (35% G+C fraction) did not show dominance but there was a very high diversity of phylotypes. Nucleotide sequence analysis revealed taxa belonging to the groups expected for the G+C contents used. The dominant phylotypes in the 63% G+C fraction were members of the Pseudomonas, Rhizobium-Agrobacterium, and Rhodospirillum assemblages, while all of the clones sequenced from the 35% G+C fraction were affiliated with several Clostridium assemblages. The two-step rDNA analysis used here uncovered more diversity than can be detected by direct rDNA analysis of total community DNA. The G+C separation step is also a way to detect some of the less dominant organisms in a community. PMID:9546163
Golub, Natalia V.; Golub, Viktor B.; Kuznetsova, Valentina G.
Abstract As of now, within the lace bug family Tingidae (Cimicomorpha), only 1.5% of the species described have been cytogenetically studied. In this paper, male karyotypes of Stephanitis caucasica, Stephanitis pyri, Physatocheila confinis, Lasiacantha capucina, Dictyla rotundata and Dictyla echii were studied using FISH mapping with an 18S rDNA marker. The results show variability: the major rDNA sites are predominantly located on a pair of autosomes but occasionally on the X and Y chromosomes. All currently available data on the distribution of the major rDNA in the Tingidae karyotypes are summarized and shortly discussed. Our main concern is to clarify whether the chromosomal position of rDNA loci can contribute to resolving the phylogenetic relationships among the Tingidae taxa. PMID:28123675
Torreira, Eva; Louro, Jaime Alegrio; Pazos, Irene; González-Polo, Noelia; Gil-Carton, David; Duran, Ana Garcia; Tosi, Sébastien; Gallego, Oriol; Calvo, Olga; Fernández-Tornero, Carlos
Cell growth requires synthesis of ribosomal RNA by RNA polymerase I (Pol I). Binding of initiation factor Rrn3 activates Pol I, fostering recruitment to ribosomal DNA promoters. This fundamental process must be precisely regulated to satisfy cell needs at any time. We present in vivo evidence that, when growth is arrested by nutrient deprivation, cells induce rapid clearance of Pol I-Rrn3 complexes, followed by the assembly of inactive Pol I homodimers. This dual repressive mechanism reverts upon nutrient addition, thus restoring cell growth. Moreover, Pol I dimers also form after inhibition of either ribosome biogenesis or protein synthesis. Our mutational analysis, based on the electron cryomicroscopy structures of monomeric Pol I alone and in complex with Rrn3, underscores the central role of subunits A43 and A14 in the regulation of differential Pol I complexes assembly and subsequent promoter association.
Torreira, Eva; Louro, Jaime Alegrio; Pazos, Irene; González-Polo, Noelia; Gil-Carton, David; Duran, Ana Garcia; Tosi, Sébastien; Gallego, Oriol; Calvo, Olga; Fernández-Tornero, Carlos
Cell growth requires synthesis of ribosomal RNA by RNA polymerase I (Pol I). Binding of initiation factor Rrn3 activates Pol I, fostering recruitment to ribosomal DNA promoters. This fundamental process must be precisely regulated to satisfy cell needs at any time. We present in vivo evidence that, when growth is arrested by nutrient deprivation, cells induce rapid clearance of Pol I–Rrn3 complexes, followed by the assembly of inactive Pol I homodimers. This dual repressive mechanism reverts upon nutrient addition, thus restoring cell growth. Moreover, Pol I dimers also form after inhibition of either ribosome biogenesis or protein synthesis. Our mutational analysis, based on the electron cryomicroscopy structures of monomeric Pol I alone and in complex with Rrn3, underscores the central role of subunits A43 and A14 in the regulation of differential Pol I complexes assembly and subsequent promoter association. DOI: http://dx.doi.org/10.7554/eLife.20832.001 PMID:28262097
Wu, Shan G; Wang, Gui T; Xi, Bing W; Xiong, Fan; Liu, Tao; Nie, Pin
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 approximately 730 bp of the first internal transcribed spacer of ribosomal DNA (ITS1 rDNA) and the 428bp 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 (
Gamerschlag, Sara; Mehlhorn, Heinz; Heukelbach, Jörg; Feldmeier, Hermann; D'Haese, Jochen
Different Tunga penetrans isolates from various hosts obtained from South America (Fortaleza. Brazil) have been studied by nucleotide sequence comparison of the first and the second internal transcribed spacer (ITS1, ITS2) of the ribosomal deoxyribonucleic acid (rDNA) and part of the mitochondrial 16S rDNA. Results show no significant host-dependent sequence differences. No indication for intraindividual and intraspecific polymorphisms could be detected. Comparing the ITS1 spacer region of T. penetrans from South America with that from Africa (Togo, Cameroon), distinct length variations have been observed caused by a repetitive sequence motif of 99 bp. The ITS1 from the South American T. penetrans contain two tandemly repeated copies, whereas four of these units are present in the spacer of the African T. penetrans. The absence of homogenization of these units indicates a recent separation of both populations. However, the different number of repetitions together with two base substitutions put the evolutionary distance of only 135 years as postulated for the transfer of T. penetrans from South America to Africa into question. Repetitive sequences could also be detected within the ITS1 rDNA region of other flea species Ctenocephalides felis, Echidnophaga gallinacea, Pulex irritans, Spilopsyllus cuniculi, and Xenopsylla cheopis. The repeat units with lengths from 10 to 99 bp are arranged in pure tandem or interspersed. The repetitive elements observed in the ITS1 of various flea species may serve as a valuable tool for phylogeographic studies.
Klier, A F; Kunst, F; Rapoport, G
A library of B. thuringiensis DNA has been prepared by using the plasmid pBR322 as a cloning vehicle and E. coli as a host cell. By screening this collection with specific probes, 17 clones were identified whose hybrid plasmids contain rRNA genes of B. thuringiensis. Several of these plasmids have been mapped with restriction endonucleases and by DNA-RNA hybridization. By using maps of overlapping fragments, we have been able to establish an overall map of the ribosomal gene cluster. Images PMID:388353
James, Stephen A.; West, Claire; Davey, Robert P.; Dicks, Jo; Roberts, Ian N.
Despite the considerable number and taxonomic breadth of past and current genome sequencing projects, many of which necessarily encompass the ribosomal DNA, detailed information on the prevalence and evolutionary significance of sequence variation in this ubiquitous genomic region are severely lacking. Here, we attempt to address this issue in two closely related yet contrasting yeast species, the baker’s yeast Saccharomyces cerevisiae and the wild yeast Saccharomyces paradoxus. By drawing on existing datasets from the Saccharomyces Genome Resequencing Project, we identify a rich seam of ribosomal DNA sequence variation, characterising 1,068 and 970 polymorphisms in 34 S. cerevisiae and 26 S. paradoxus strains respectively. We discover the two species sets exhibit distinct mutational profiles. Furthermore, we show for the first time that unresolved rDNA sequence variation resulting from imperfect concerted evolution of the ribosomal DNA region follows a U-shaped allele frequency distribution in each species, similar to loci that evolve under non-concerted mechanisms but arising through rather different evolutionary processes. Finally, we link differences between the shapes of these allele frequency distributions to the two species’ contrasting population histories. PMID:27345953
Parel, Joan Dee C; Galula, Jedhan U; Ooi, Hong-Kean
To differentiate the morphologically similar pinworms of the common laboratory rodents, such as Syphacia obvelata and Syphacia muris, we amplified and sequenced the region spanning the internal transcribed spacer 1 (ITS-1), 5.8S gene, and ITS-2 of the ribosomal DNA followed by designing of species-specific primers for future use in the identification of the worms. It was observed that S. obvelata, S. muris and Aspiculuris tetraptera can be differentiated from each other based on their rDNA sequences. This is the first report of the ITS-1, 5.8S, and ITS-2 of the rDNA of the three aforementioned rodent pinworm species. The use of restriction endonucleases, AluI or RsaI, further allowed the delineation of the three species. Moreover, we also constructed species-specific primers that were designed for unique regions of the ITS-2 of the three species. This approach allowed their specific identification with no amplicons being amplified from heterogenous DNA samples, and sequencing confirmed the identity of the sequences amplified. Thus, the use of these specific primers along with PCR-RFLP can serve as useful tools for the identification of pinworms in rats, mice, and wild rodents.
Pérez-González, C E; Eickbush, T H
The mobile elements R1 and R2 insert specifically into the rRNA gene locus (rDNA locus) of arthropods, a locus known to undergo concerted evolution, the recombinational processes that preserve the sequence homogeneity of all repeats. To monitor how rapidly individual R1 and R2 insertions are turned over in the rDNA locus by these processes, we have taken advantage of the many 5' truncation variants that are generated during the target-primed reverse transcription mechanism used by these non-LTR retrotransposons for their integration. A simple PCR assay was designed to reveal the pattern of the 5' variants present in the rDNA loci of individual X chromosomes in a population of Drosophila simulans. Each rDNA locus in this population was found to have a large, unique collection of 5' variants. Each variant was present at low copy number, usually one copy per chromosome, and was seldom distributed to other chromosomes in the population. The failure of these variants to spread to other units in the same rDNA locus suggests a strong recombinational bias against R1 and R2 that results in the individual copies of these elements being rapidly lost from the rDNA locus. This bias suggests a significantly higher frequency of R1 and R2 retrotransposition than we have previously suggested. PMID:11514447
Dichamp, Isabelle; Séité, Paule; Agius, Gérard; Barbarin, Alice; Beby-Defaux, Agnès
High-risk human papillomavirus oncoproteins E6 and E7 play a major role in HPV-related cancers. One of the main functions of E7 is the degradation of pRb, while E6 promotes the degradation of p53, inactivating the p14ARF-p53 pathway. pRb and p14ARF can repress ribosomal DNA (rDNA) transcription in part by targeting the Upstream Binding Factor 1 (UBF1), a key factor in the activation of RNA polymerase I machinery. We showed, through ectopic expression and siRNA silencing of p14ARF and/or E7, that E7 stimulates UBF1-mediated rDNA gene transcription, partly because of increased levels of phosphorylated UBF1, preventing the inhibitory function of p14ARF. Unexpectedly, activation of rDNA gene transcription was higher in cells co-expressing p14ARF and E7, compared to cells expressing E7 alone. We did not find a difference in P-UBF1 levels that could explain this data. However, p14ARF expression induced E7 to accumulate into the nucleolus, where rDNA transcription takes place, providing an opportunity for E7 to interact with nucleolar proteins involved in this process. GST-pull down and co-immunoprecipitation assays showed interactions between p14ARF, UBF1 and E7, although p14ARF and E7 are not able to directly interact. Co-expression of a pRb-binding-deficient mutant (E7C24G) and p14ARF resulted in EC24G nucleolar accumulation, but not in a significant higher activation of rDNA transcription, suggesting that the inactivation of pRb is involved in this phenomenon. Thus, p14ARF fails to prevent E7-mediated UBF1 phosphorylation, but could facilitate nucleolar pRb inactivation by targeting E7 to the nucleolus. While others have reported that p19ARF, the mouse homologue of p14ARF, inhibits some functions of E7, we showed that E7 inhibits a p53-independent function of p14ARF. These results point to a mutually functional interaction between p14ARF and E7 that might partly explain why the sustained p14ARF expression observed in most cervical pre-malignant lesions and
Ro, K E; Keener, C S; McPheron, B A
There are only a small number of molecular markers currently proven to be useful for phylogenetic inference within the flowering plants. We demonstrate that the 5' end of the 26S ribosomal DNA (ca. 1100 bp) is of great value for investigating generic to subfamilial relationships. We analyzed DNA sequences from 31 species of the Ranunculaceae and four species of the Berberidaceae to test phylogenetic relationships within the Ranunculaceae. The inferred phylogeny strongly supports the concept that the Thalictrum chromosome group is not monophyletic, but consists of three independent lineages: (1) Hydrastis, (2) Xanthorhiza and Coptis, and (3) Thalictrum, Aquilegia, and Enemion. Based on comparison with conventional taxonomic characters, we propose a hypothesis that the third group also includes the rest of the Thalictrum chromosome taxa that have a base chromosome number of seven. For the Ranunculus chromosome group, our study suggests several relationships that have not been recognized by conventional systematics. The inferred 26S rDNA topology is compared with results from two previously published molecular data sets: DNA sequences from rbcL, atpB, and 18S rDNA genes and restriction fragment length polymorphism data from chloroplast DNA. The three topologies are highly congruent and agree with karyological characters, but not with fruit type, both of which have often been used for the higher classification of the Ra- nunculaceae.
Huang, W Y; He, B; Wang, C R; Zhu, X Q
Isolates of Fasciola (Platyhelminthes: Trematoda: Digenea) from different host species and geographical locations in Mainland China were characterised genetically. The second internal transcribed spacer (ITS-2) of nuclear ribosomal DNA (rDNA) was amplified from individual trematodes by polymerase chain reaction (PCR), and the representative amplicons were cloned and sequenced. The length of the ITS-2 sequences was 361-362bp for all Chinese Fasciola specimens sequenced. While there was no variation in length or composition of the ITS-2 sequences among multiple specimens from France, Sichuan and Guangxi, sequence difference of 1.7% (6/362) was detected between specimens from France and Sichuan, and those from Guangxi. Based on ITS-2 sequence data, it was concluded that the Fasciola from Sichuan represented Fasciola hepatica, the one from Guangxi represented Fasciola gigantica and the one from sheep from Heilongjiang may represent an "intermediate genotype", as its ITS-2 sequences were unique in that two different ITS-2 sequences exist in the rDNA array within a single Fasciola worm. One of the sequences is identical to that of F. hepatica, and the other is almost identical to that of F. gigantica in that nucleotides at five of the six polymorphic positions represent F. gigantica. This microheterogeneity is possibly due to sequence polymorphism among copies of the ITS-2 array within the same worm. Based on the sequence differences, a PCR-linked restriction fragment length polymorphism (PCR-RFLP) assay was established for the unequivocal delineation of the Fasciola spp. from Mainland China using restriction endonuclease Hsp92II or RcaI. This assay should provide a valuable tool for the molecular identification and for studying the ecology and population genetic structures of Fasciola spp. from Mainland China and elsewhere.
Spaller, Thomas; Groth, Marco; Glöckner, Gernot; Winckler, Thomas
The amoeba Dictyostelium discoideum has a haploid genome in which two thirds of the DNA encodes proteins. Consequently, the space available for selfish mobile elements to expand without excess damage to the host genome is limited. The non-long terminal repeat retrotransposon TRE5-A maintains an active population in the D. discoideum genome and apparently adapted to this gene-dense environment by targeting positions ~47 bp upstream of tRNA genes that are devoid of protein-coding regions. Because only ~24% of tRNA genes are associated with a TRE5-A element in the reference genome, we evaluated whether TRE5-A retrotransposition is limited to this subset of tRNA genes. We determined that a tagged TRE5-A element (TRE5-Absr) integrated at 384 of 405 tRNA genes, suggesting that expansion of the current natural TRE5-A population is not limited by the availability of targets. We further observed that TRE5-Absr targets the ribosomal 5S gene on the multicopy extrachromosomal DNA element that carries the ribosomal RNA genes, indicating that TRE5-A integration may extend to the entire RNA polymerase III (Pol III) transcriptome. We determined that both natural TRE5-A and cloned TRE5-Absr retrotranspose to locations on the extrachromosomal rDNA element that contain tRNA gene-typical A/B box promoter motifs without displaying any other tRNA gene context. Based on previous data suggesting that TRE5-A targets tRNA genes by locating Pol III transcription complexes, we propose that A/B box loci reflect Pol III transcription complex assembly sites that possess a function in the biology of the extrachromosomal rDNA element.
Kagawa, S; Nagano, Y; Tazumi, A; Murayama, O; Millar, B C; Moore, J E; Matsuda, M
The primer set for 16S rDNA amplified an amplicon of about 1500 bp in length for three strains of Taylorella equigenitalis (NCTC11184(T), Kentucky188 and EQ59). Sequence differences of the 16S rDNA among the six sequences, including three reference sequences, occurred at only a few nucleotide positions and thus, an extremely high sequence similarity of the 16S rDNA was first demonstrated among the six sequences. In addition, the primer set for 16S-23S rDNA internal spacer region (ISR) amplified two amplicons about 1300 bp and 1200 bp in length for the three strains. The ISRs were estimated to be about 920 bp in length for large ISR-A and about 830 bp for small ISR-B. Sequence alignment of the ISR-A and ISR-B demonstrated about 10 base differences between NCTC11184(T) and EQ59 and between Kentucky188 and EQ59. However, only minor sequence differences were demonstrated between the ISR-A and ISR-B from NCTC11184(T) and Kentucky188, respectively. A typical order of the intercistronic tRNAs with the 29 nucleotide spacer of 5'-16S rDNA-tRNA(Ile)-tRNA(Ala)-23S rDNA-3' was demonstrated in the all ISRs. The ISRs may be useful for the discrimination amongst isolates of T. equigenitalis if sequencing is employed.
Gregarine 18S ribosomal DNA trees are hard to resolve because they exhibit the most disparate rates of rDNA evolution of any eukaryote group. As site-heterogeneous tree-reconstruction algorithms can give more accurate trees, especially for technically unusually challenging groups, I present the first site-heterogeneous rDNA trees for 122 gregarines and an extensive set of 452 appropriate outgroups. While some features remain poorly resolved, these trees fit morphological diversity better than most previous, evolutionarily less realistic, maximum likelihood trees. Gregarines are probably polyphyletic, with some 'eugregarines' and all 'neogregarines' (both abandoned as taxa) being more closely related to Cryptosporidium and Rhytidocystidae than to archigregarines. I establish a new subclass Orthogregarinia (new orders Vermigregarida, Arthrogregarida) for gregarines most closely related to Cryptosporidium and group Orthogregarinia, Cryptosporidiidae, and Rhytidocystidae as revised class Gregarinomorphea. Archigregarines are excluded from Gregarinomorphea and grouped with new orders Velocida (Urosporoidea superfam. n. and Veloxidium) and Stenophorida as a new sporozoan class Paragregarea. Platyproteum and Filipodium never group with Orthogregarinia or Paragregarea and are sufficiently different morphologically to merit a new order Squirmida. I revise gregarine higher-level classification generally in the light of site-heterogeneous-model trees, discuss their evolution, and also sporozoan cell structure and life-history evolution, correcting widespread misinterpretations.
Ribeiro, Leila Braga; Moraes Neto, Americo; Artoni, Roberto Ferreira; Matoso, Daniele Aparecida; Feldberg, Eliana
Some species of Characiformes are known for their high economic value, such as Colossoma macropomum and Piaractus mesopotamicus, and are used in aquaculture programs to generate hybrid tambacu (interbreeding of C. macropomum females and P. mesopotamicus males). The present work aimed to investigate the location of the Rex3 and Rex6 transposable elements in the hybrid and in the species, in addition to checking the genomic organization of the 18S and 5S rDNA in tambacu. The diploid number found for the hybrid was equal to 54 chromosomes, with heterochromatic blocks distributed mainly in the centromeric portions. The chromosomal location of the mobile elements Rex3 and Rex6 in C. macropomum, P. mesopotamicus, and in the hybrid between these species enabled knowledge expansion and the generation of data on such mobile elements. In addition, the location of such elements is not related to the distribution of ribosomal DNA sites. The mapping of the 18S rDNA was shown to be effective in cytogenetic identification of the hybrid tambacu, allowing for differentiation from the parent species and from the hybrid between C. macropomum and the other species from Piaractus (P. brachypomus).
Shu, Fan-Fan; Lv, Rui-Qing; Zhang, Yi-Fang; Duan, Gang; Wu, Ding-Yu; Li, Bi-Feng; Yang, Jian-Fa; Zou, Feng-Cai
On mainland China, liver flukes of Fasciola spp. (Digenea: Fasciolidae) can cause serious acute and chronic morbidity in numerous species of mammals such as sheep, goats, cattle, and humans. The objective of the present study was to examine the taxonomic identity of Fasciola species in Yunnan province by sequences of the first and second internal transcribed spacers (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA). The ITS rDNA was amplified from 10 samples representing Fasciola species in cattle from 2 geographical locations in Yunnan Province, by polymerase chain reaction (PCR), and the products were sequenced directly. The lengths of the ITS-1 and ITS-2 sequences were 422 and 361-362 base pairs, respectively, for all samples sequenced. Using ITS sequences, 2 Fasciola species were revealed, namely Fasciola hepatica and Fasciola gigantica. This is the first demonstration of F. gigantica in cattle in Yunnan Province, China using a molecular approach; our findings have implications for studying the population genetic characterization of the Chinese Fasciola species and for the prevention and control of Fasciola spp. in this province.
Hausner, Georg; Wang, Xi
The internal transcribed spacers of the ribosomal DNA tandem repeat were examined in members of the ascomycetous genus Sphaeronaemella. Species of Sphaeronaemella and its mitotic counterpart Gabarnaudia, have a compact rDNA gene arrangement due to unusually short internal transcribed spacer (ITS) regions. Examination of these regions from phylogenetically related taxa, Cornuvesica, Gondwanamyces, and Ceratocystis, showed that their ITS1 and ITS2 regions could be folded into central hairpin-like structures with the size reduction in species of Sphaeronaemella being due to length reduction of the main-hairpin and the loss of smaller hairpin-like structures that emanate from the main hairpin. A databank compilation, combined with newly obtained sequences, provided an ITS data set that includes sequences of 600 species belonging to the Ascomycota. Correlation analysis revealed that the sizes of ITS1 and ITS2 show a strong positive correlation, suggesting that the 2 rDNA regions have co-evolved. This supports biochemical evidence indicating that the ITS1 and ITS2 segments interact to facilitate the maturation of the rRNA precursor.
Ben Othmen, A; Said, K; Ben Alp, Z; Chatti, N; Ready, P D
Tunisian Androctonus species, for long time discussed, were recognized on the basis of mitochondrial 16S rDNA sequences. Although the analysed nucleotide sequence is rather short (about 300 bp), the obtained phlogenetic trees revealed that A. amoreuxi and A. aeneas form two well-supported sister clades against A. australis haplotypes. Each specimen of the very rare species A. aeneas showed a specific haplotype, but together formed a well-defined clade. Some A. amoreuxi specimens highlighted unidirectional mitochondrial introgression from neighbouring A. australis population. Within A. australis, previously described, subspecies subdivision (A. a .hector and A. a. garzonii) was not supported.
Righetti, Pier Giorgio; Casale, Elena; Carter, Daniel; Snyder, Robert S.; Wenisch, Elisabeth; Faupel, Michel
Recombinant-DNA (deoxyribonucleic acid) (r-DNA) proteins, produced in large quantities for human consumption, are now available in sufficient amounts for crystal growth. Crystallographic analysis is the only method now available for defining the atomic arrangements within complex biological molecules and decoding, e.g., the structure of the active site. Growing protein crystals in microgravity has become an important aspect of biology in space, since crystals that are large enough and of sufficient quality to permit complete structure determinations are usually obtained. However even small amounts of impurities in a protein preparation are anathema for the growth of a regular crystal lattice. A multicompartment electrolyzer with isoelectric, immobiline membranes, able to purify large quantities of r-DNA proteins is described. The electrolyzer consists of a stack of flow cells, delimited by membranes of very precise isoelectric point (pI, consisting of polyacrylamide supported by glass fiber filters containing Immobiline buffers and titrants to uniquely define a pI value) and very high buffering power, able to titrate all proteins tangent or crossing such membranes. By properly selecting the pI values of two membranes delimiting a flow chamber, a single protein can be kept isoelectric in a single flow chamber and thus, be purified to homogeneity (by the most stringent criterion, charge homogeneity).
Monkheang, Pansa; Chaveerach, Arunrat; Sudmoon, Runglawan; Tanee, Tawatchai
Abstract Scadoxus multiflorus Martyn, 1795 is an ornamental plant with brilliantly colored flowers. Even though its chromosomes are rather large, there is no karyotype description reported so far. Therefore, conventional and molecular cytogenetic studies including fluorescence in situ hybridization (FISH) with 45S and 5S rDNA, and human telomere sequence (TTAGGG)n probes (Arabidopsis-type telomere probes yielded negative results) were carried out. The chromosome number is as reported previously, 2n = 18. The nine chromosome pairs include two large submetacentric, five large acrocentric, one medium acrocentric, two small metacentric and eight small submetacentric chromosomes. Hybridization sites of the 45S rDNA signals were on the short arm ends of chromosomes #1, #3 and #8, while 5S rDNA signals appeared on the long arm of chromosome 3, in one homologue as a double signal. The telomere signals were restricted to all chromosome ends. Three chromosome pairs could be newly identified, chromosome pair 3 by 5S rDNA and chromosomes #1, #3 and #8 by 45S rDNA loci. In addition to new information about rDNA locations we show that the ends of Scadoxus multiflorus chromosomes harbor human instead of Arabidopsis-type telomere sequences. Overall, the Scadoxus multiflorus karyotype presents chromosomal heteromorphy concerning size, shape and 45S and 5S rDNA positioning. As Scadoxus Rafinesque, 1838 and related species are poorly studied on chromosomal level the here presented data is important for better understanding of evolution in Amaryllidaceae. PMID:28123684
Background Grasshoppers from the Romaleidae family are well distributed in the Neotropical Region and represent a diversified and multicolored group in which the karyotype is conserved. Few studies have been conducted to understand the evolutionary dynamics of multigene families. Here, we report the chromosomal locations of the 18S and 5S rDNA and H3 histone multigene families in four grasshopper species from the Romaleidae family, revealed by fluorescent in situ hybridization (FISH). Results The 5S rDNA gene was located in one or two chromosome pairs, depending on the species, and was found in a basal distribution pattern. Its chromosomal location was highly conserved among these species. The 18S rDNA was located in a single medium-sized chromosomal pair in all species analyzed. Its chromosomal location was near the centromere in the proximal or pericentromeric regions. The location of the H3 histone gene was highly conserved, with slight chromosomal location differences among some species. To our knowledge, this is the first report of a megameric chromosome carrying both the chromosomal markers 18S rDNA and the H3 histone genes, thereby expanding our understanding of such chromosomes. Conclusions The 5S and 18S rDNA genes and the H3 histone genes showed a conservative pattern in the species that we analyzed. A basal distribution pattern for 5S rDNA was observed with a location on the fourth chromosomal pair, and it was identified as the possible ancestral bearer. The 18S rDNA and H3 histone genes were restricted to a single pair of chromosomes, representing an ancestral pattern. Our results reinforce the known taxonomic relationships between Chromacris and Xestotrachelus, which are two close genera. PMID:24090216
Sánchez-Gorostiaga, Alicia; López-Estraño, Carlos; Krimer, Dora B.; Schvartzman, Jorge B.; Hernández, Pablo
Polar replication fork barriers (RFBs) near the 3′ end of the rRNA transcriptional unit are a conserved feature of ribosomal DNA (rDNA) replication in eukaryotes. In the mouse, in vivo studies indicate that the cis-acting Sal boxes required for rRNA transcription termination are also involved in replication fork blockage. On the contrary, in the budding yeast Saccharomyces cerevisiae, the rRNA transcription termination factors are not required for RFBs. Here we characterized the rDNA RFBs in the fission yeast Schizosaccharomyces pombe. S. pombe rDNA contains three closely spaced polar replication barriers named RFB1, RFB2, and RFB3 in the 3′ to 5′ order. The transcription termination protein reb1 and its two binding sites, present at the 3′ end of the coding region, were required for fork arrest at RFB2 and RFB3 in vivo. On the other hand, fork arrest at the strongest RFB1 barrier was independent of the above transcription termination factors. Therefore, RFB2 and RFB3 resemble the barriers present in the mouse rDNA, whereas RFB1 is similar to the budding yeast RFBs. These results suggest that during evolution, cis- and trans-acting factors required for rRNA transcription termination became involved in replication fork blockage also. S. pombe is suggested to be a transitional species in which both mechanisms coexist. PMID:14673172
Mukha, D V; Kagramanova, A S; Lazebnaya, I V; Lazebnyi, O E; Vargo, E L; Schal, C
Little information is available on genetic variation within and between populations of pest cockroaches. In this study, intraspecific HindIII polymorphism was investigated in the German cockroach, Blattella germanica (Linnaeus) (Dictyoptera, Blattaria: Blattellidae), using restriction fragment length polymorphisms (RFLP) of the non-transcribed spacer (NTS) region of ribosomal DNA (rDNA). Individual male insects were collected from infestations at three different pig farms. Each population was characterized by HindIII restriction fragment frequencies and haplotype (a particular X-chromosome pattern) frequencies. The inheritance of the X-chromosome HindIII rDNA patterns over 12 generations (3 years) follows Mendelian patterns, and the stability of this polymorphic marker indicates infrequent genetic recombination of variable sites. Although pairwise genetic distance measures were uncorrelated with geographical distance, the pattern of genetic differentiation of the three cockroach populations suggests that human-mediated transport of cockroaches is an important force in shaping the population genetic structure of cockroach infestations, at least at the regional scale of 10-100 km. Sequence variation in the ribosomal NTS is a useful marker, and RFLP of rDNA is a simple, robust and reproducible technique for differentiating recently diverged cockroach populations.
Lan, Hong; Chen, Chun-Li; Miao, Yin; Yu, Chang-Xiu; Guo, Wen-Wu; Xu, Qiang; Deng, Xiu-Xin
Citrus sinensis chromosomes present a morphological differentiation of bands after staining by the fluorochromes CMA and DAPI, but there is still little information on its chromosomal characteristics. In this study, the chromosomes in 'Valencia' C. sinensis were analyzed by fluorescence in situ hybridization (FISH) using telomere DNA and the 45S rDNA gene as probes combining CMA/DAPI staining, which showed that there were two fragile sites in sweet orange chromosomes co-localizing at distended 45S rDNA regions, one proximally locating on B-type chromosome and the other subterminally locating on D-type chromosome. While the chromosomal CMA banding and 45S rDNA FISH mapping in the doubled haploid line of 'Valencia' C. sinensis indicated six 45S rDNA regions, four were identified as fragile sites as doubled comparing its parental line, which confirmed the cytological heterozygosity and chromosomal heteromorphisms in sweet orange. Furthermore, Ag-NOR identified two distended 45S rDNA regions to be active nucleolar organizing regions (NORs) in diploid 'Valencia' C. sinensis. The occurrence of quadrivalent in meiosis of pollen mother cells (PMCs) in 'Valencia' sweet orange further confirmed it was a chromosomal reciprocal translocation line. We speculated this chromosome translocation was probably related to fragile sites. Our data provide insights into the chromosomal characteristics of the fragile sites in 'Valencia' sweet orange and are expected to facilitate the further investigation of the possible functions of fragile sites.
Schwelm, Arne; Berney, Cédric; Dixelius, Christina; Bass, David; Neuhauser, Sigrid
Clubroot disease caused by Plasmodiophora brassicae is one of the most important diseases of cultivated brassicas. P. brassicae occurs in pathotypes which differ in the aggressiveness towards their Brassica host plants. To date no DNA based method to distinguish these pathotypes has been described. In 2011 polymorphism within the 28S rDNA of P. brassicae was reported which potentially could allow to distinguish pathotypes without the need of time-consuming bioassays. However, isolates of P. brassicae from around the world analysed in this study do not show polymorphism in their LSU rDNA sequences. The previously described polymorphism most likely derived from soil inhabiting Cercozoa more specifically Neoheteromita-like glissomonads. Here we correct the LSU rDNA sequence of P. brassicae. By using FISH we demonstrate that our newly generated sequence belongs to the causal agent of clubroot disease. PMID:27750174
Wei Wang, Mi Sun
Neighbor-joining, maximum-parsimony, minimum-evolution, maximum-likelihood and Bayesian trees constructed based on 16S rDNA sequences of 181 type strains of Bacillus species and related taxa manifested nine phylogenetic groups. The phylogenetic analysis showed that Bacillus was not a monophyletic group. B. subtilis was in Group 1. Group 4, 6 and 8 respectively consisted of thermophiles, halophilic or halotolerant bacilli and alkaliphilic bacilli. Group 2, 4 and 8 consisting of Bacillus species and related genera demonstrated that the current taxonomic system did not agree well with the 16S rDNA evolutionary trees. The position of Caryophanaceae and Planococcaceae in Group 2 suggested that they might be transferred into Bacillaceae, and the heterogeneity of Group 2 implied that some Bacillus species in it might belong to several new genera. Group 9 was mainly comprised of the genera (excluding Bacillus) of Bacillaceae, so some Bacillus species in Group 9: B. salarius, B. qingdaonensis and B. thermcloacae might not belong to Bacillus. Four Bacillus species, B. schlegelii, B. tusciae, B. edaphicus and B. mucilaginosus were clearly placed outside the nine groups. PMID:24031394
Cao, Boyang; Wang, Min; Liu, Lei; Zhou, Zhemin; Wen, Shaoping; Rozalski, Antoni; Wang, Lei
Proteus is a Gram-negative, facultative anaerobic bacterium. In this study, 813 Proteus 16S-23S rDNA internal transcribed spacer (ITS) sequences were determined from 46 Proteus strains, including 388 ITS from 22 P. mirabilis strains, 211 ITS from 12 P. vulgaris strains, 169 ITS from 10 P. penneri strains, and 45 ITS from 2 P. myxofaciens strains. The Proteus strains carry mainly two types of ITS, ITS(Glu) (containing tRNA(Glu (UUC)) gene) and ITS(Ile+Ala) (containing tRNA(Ile (GAU)) and tRNA(Ala (UGC)) gene), and are in the forms of 28 variants with 25 genomic origins. The ITS sequences are a mosaic-like structure consisting of three conservative regions and two variable regions. The nucleotide identity of ITS subtypes in strains of the same species ranges from 96.2% to 100%. The divergence of Proteus ITS divergence was most likely due to intraspecies recombinations or horizontal transfers of sequence blocks. The phylogenetic relationship deduced from the second variable region of ITS sequences of the three facultative human pathogenic species P. mirabilis, P. vulgaris and P. penneri is similar with that based on 16S rDNA sequences, but has higher resolution to differentiate closely related P. vulgaris and P. penneri. This study is the first comprehensive study of ITS in four Proteus species and laid solid foundation for the development of high-throughput technology for quick and accurate identification of the important foodborne and nosocomial pathogens.
Burleigh, J. Gordon; Light, Jessica E.; Reed, David L.
Phylogenetic trees can reveal the origins of endosymbiotic lineages of bacteria and detect patterns of co-evolution with their hosts. Although taxon sampling can greatly affect phylogenetic and co-evolutionary inference, most hypotheses of endosymbiont relationships are based on few available bacterial sequences. Here we examined how different sampling strategies of Gammaproteobacteria sequences affect estimates of the number of endosymbiont lineages in parasitic sucking lice (Insecta: Phthirapatera: Anoplura). We estimated the number of louse endosymbiont lineages using both newly obtained and previously sequenced 16S rDNA bacterial sequences and more than 42,000 16S rDNA sequences from other Gammaproteobacteria. We also performed parametric and nonparametric bootstrapping experiments to examine the effects of phylogenetic error and uncertainty on these estimates. Sampling of 16S rDNA sequences affects the estimates of endosymbiont diversity in sucking lice until we reach a threshold of genetic diversity, the size of which depends on the sampling strategy. Sampling by maximizing the diversity of 16S rDNA sequences is more efficient than randomly sampling available 16S rDNA sequences. Although simulation results validate estimates of multiple endosymbiont lineages in sucking lice, the bootstrap results suggest that the precise number of endosymbiont origins is still uncertain. PMID:27547523
Gokhman, Vladimir E; Anokhin, Boris A; Kuznetsova, Valentina G
Karyotypes of six species belonging to three main clades of parasitoid Hymenoptera, the superfamilies Ichneumonoidea (Ichneumonidae: Ichneumon amphibolus), Cynipoidea (Cynipidae: Diplolepis rosae) and Chalcidoidea (Eurytomidae: Eurytoma robusta, Eu. serratulae and Eu. compressa, and Torymidae: Torymus bedeguaris) were studied using FISH with 18S rDNA and telomeric (TTAGG)n probes. Haploid karyotypes of D. rosae, Eu. robusta and Eu. serratulae carried the only 18S rDNA hybridization signal, whereas those of I. amphibolus and Eu. compressa carried three and two rDNA clusters respectively. In addition, three rDNA sites were visualized in the aneuploid female of T. bedeguaris. The number of rDNA clusters in parasitoid Hymenoptera generally correlates to the chromosome number. Apart from the overwhelming majority of the studied species of aculeate Hymenoptera, no hybridization signals were obtained from FISH with the telomeric (TTAGG)n probe in the examined parasitoid species. These data suggest absence of the canonical (TTAGG)n insect telomeric motif in the Ichneumonoidea, Cynipoidea and Chalcidoidea, and perhaps in parasitoid Hymenoptera in general.
A unique DNA repair and recombination gene (recN) sequence for identification and intraspecific molecular typing of bacterial wilt pathogen Ralstonia solanacearum and its comparative analysis with ribosomal DNA sequences.
Kumar, Aundy; Prameela, Thekkan Puthiyaveedu; Suseelabhai, Rajamma
Ribosomal gene sequences are a popular choice for identification of bacterial species and, often, for making phylogenetic interpretations. Although very popular, the sequences of 16S rDNA and 16-23S intergenic sequences often fail to differentiate closely related species of bacteria. The availability of complete genome sequences of bacteria, in the recent years, has accelerated the search for new genome targets for phylogenetic interpretations. The recently published full genome data of nine strains of R. solanacearum, which causes bacterial wilt of crop plants, has provided enormous genomic choices for phylogenetic analysis in this globally important plant pathogen. We have compared a gene candidate recN, which codes for DNA repair and recombination function, with 16S rDNA/16-23S intergenic ribosomal gene sequences for identification and intraspecific phylogenetic interpretations in R. solanacearum. recN gene sequence analysis of R. solanacearum revealed subgroups within phylotypes (or newly proposed species within plant pathogenic genus, Ralstonia), indicating its usefulness for intraspecific genotyping. The taxonomic discriminatory power of recN gene sequence was found to be superior to ribosomal DNA sequences. In all, the recN-sequence-based phylogenetic tree generated with the Bayesian model depicted 21 haplotypes against 15 and 13 haplotypes obtained with 16S rDNA and 16-23S rDNA intergenic sequences, respectively. Besides this, we have observed high percentage of polymorphic sites (S 23.04%), high rate of mutations (Eta 276) and high codon bias index (CBI 0.60), which makes the recN an ideal gene candidate for intraspecific molecular typing of this important plant pathogen.
Maryańska-Nadachowska, Anna; Anokhin, Boris A.; Gnezdilov, Vladimir M.; Kuznetsova, Valentina G.
Abstract We report several chromosomal traits in 11 species from 8 genera of the planthopper family Issidae, the tribes Issini, Parahiraciini and Hemisphaeriini. All species present a 2n = 27, X(0) chromosome complement known to be ancestral for the family. The karyotype is conserved in structure and consists of a pair of very large autosomes; the remaining chromosomes gradually decrease in size and the X chromosome is one of the smallest in the complement. For selected species, analyses based on C-, AgNOR- and CMA3-banding techniques were also carried out. By fluorescence in situ hybridization, the (TTAGG)n probe identified telomeres in all species, and the major rDNA loci were detected on the largest pair of autosomes. In most species, ribosomal loci were found in an interstitial position while in two species they were located in telomeric regions suggesting that chromosomal rearrangements involving the rDNA segments occurred in the evolution of the family Issidae. Furthermore, for 8 species the number of testicular follicles is provided for the first time. PMID:27830046
Phylogenetic study of Baylisascaris schroederi isolated from Qinling subspecies of giant panda in China based on combined nuclear 5.8S and the second internal transcribed spacer (ITS-2) ribosomal DNA sequences.
Zhao, Guang-Hui; Li, Hong-Mei; Ryan, Una M; Cong, Mei-Mei; Hu, Bing; Gao, Man; Ren, Wan-Xin; Wang, Xing-Ye; Zhang, Shui-Ping; Lin, Qing; Zhu, Xing-Quan; Yu, San-Ke
The nuclear ribosomal DNA (rDNA) region spanning 5.8S rDNA and the second internal transcribed spacer (ITS-2) of Baylisascaris schroederi isolated from the Qinling subspecies of giant panda in Shaanxi Province, China were amplified and sequenced. Sequence variations in the two rDNA regions within B. schroederi and among species in the family Ascarididae were examined. The lengths of B. schroederi 5.8S and ITS-2 rDNA sequences were 156 bp and 327 bp, respectively, and no nucleotide variation was found in these two rDNA regions among the 20 B. schroederi samples examined, and these ITS-2 sequences were identical to that of B. schroederi isolated from giant panda in Sichuan province, China. The inter-species differences in 5.8S and ITS-2 rDNA sequences among members of the family Ascarididae were 0-1.3% and 0-17.7%, respectively. Phylogenetic relationships among species in the Ascarididae were re-constructed by Bayesian inference (Bayes), maximum parsimony (MP), and maximum likelihood (ML) analyses, based on combined sequences of 5.8S and ITS-2 rDNA. All B. schroederi samples clustered together and sistered to B. transfuga with high posterior probabilities/bootstrap values, which further confirmed that nematodes isolated from the Qinling subspecies of giant panda in Shaanxi Province, China represent B. schroederi. Because of the large number of ambiguously aligned sequence positions (difficulty of inferring homology by positions), ITS-2 sequence alone is likely unsuitable for phylogenetic analyses at the family level, but the combined 5.8S and ITS-2 rDNA sequences provide alternative genetic markers for the identification of B. schroederi and for phylogenetic analysis of parasites in the family Ascarididae.
Ding, Xiao-Liu; Xu, Ting-Liang; Wang, Jing; Luo, Le; Yu, Chao; Dong, Gui-Min; Pan, Hui-Tang; Zhang, Qi-Xiang
To elucidate the evolutionary dynamics of the location and number of rDNA loci in the process of polyploidization in the genus Rosa, we examined 45S rDNA sites in the chromosomes of 6 modern rose cultivars (R. hybrida), 5 R. rugosa cultivars, and 20 hybrid progenies by fluorescence in situ hybridization. Variation in the number of rDNA sites in parents and their interspecific hybrids was detected. As expected, 4 rDNA sites were observed in the genomes of 4 modern rose cultivars, while 3 hybridization sites were observed in the 2 others. Two expected rDNA sites were found in 2 R. rugosa cultivars, while in the other 3 R. rugosa cultivars 4 sites were present. Among the 20 R. hybrida × R. rugosa offspring, 13 carried the expected number of rDNA sites, and 1 had 6 hybridization sites, which exceeded the expected number by far. The other 6 offspring had either 2 or 3 hybridization sites, which was less than expected. Differences in the number of rDNA loci were observed in interspecific offspring, indicating that rDNA loci exhibit instability after distant hybridization events. Abnormal chromosome pairing may be the main factor explaining the variation in rDNA sites during polyploidization.
Ouellette, A.J.; Moonka, R.; Zelenetz, A.; Malt, R.A.
The overall rate of rDNA transcription increases by 50% during the first 24 hours of compensatory renal hypertrophy in the mouse. To study mechanisms of ribosome accumulation after uninephrectomy, transcription rates were measured in isolated kidneys by transcriptional runoff. /sup 32/P-labeled nascent transcripts were hybridized to blots containing linearized, denatured cloned rDNA, and hybridization was quantitated autoradiographically and by direct counting. Overall transcriptional activity of rDNA was increased by 30% above control levels at 6 hrs after nephrectomy and by 50% at 12, 18, and 24 hrs after operation. Hybridizing RNA was insensitive to inhibiby alpha-amanitin, and no hybridization was detected to vector DNA. Thus, accelerated rDNA transcription is one regulatory element in the accretion of ribosomes in renal growth, and the regulatory event is an early event. Mechanisms of activation may include enhanced transcription of active genes or induction of inactive DNA.
Tuskan, Gerald A; Gunter, Lee E; DiFazio, Stephen P
The 18S-28S rDNA and 5S rDNA loci in Populus trichocarpa were localized using fluorescent in situ hybridization (FISH). Two 18S-28S rDNA sites and one 5S rDNA site were identified and located at the ends of 3 different chromosomes. FISH signals from the Arabidopsis -type telomere repeat sequence were observed at the distal ends of each chromosome. Six BAC clones selected from 2 linkage groups based on genome sequence assembly (LG-I and LG-VI) were localized on 2 chromosomes, as expected. BACs from LG-I hybridized to the longest chromosome in the complement. All BAC positions were found to be concordant with sequence assembly positions. BAC-FISH will be useful for delineating each of the Populus trichocarpa chromosomes and improving the sequence assembly of this model angiosperm tree species.
Islam-Faridi, M N; Nelson, C D; DiFazio, S P; Gunter, L E; Tuskan, G A
The 18S-28S rDNA and 5S rDNA loci in Populus trichocarpa were localized using fluorescent in situ hybridization (FISH). Two 18S-28S rDNA sites and one 5S rDNA site were identified and located at the ends of 3 different chromosomes. FISH signals from the Arabidopsis-type telomere repeat sequence were observed at the distal ends of each chromosome. Six BAC clones selected from 2 linkage groups based on genome sequence assembly (LG-I and LG-VI) were localized on 2 chromosomes, as expected. BACs from LG-I hybridized to the longest chromosome in the complement. All BAC positions were found to be concordant with sequence assembly positions. BAC-FISH will be useful for delineating each of the Populus trichocarpa chromosomes and improving the sequence assembly of this model angiosperm tree species.
Zhao, Ya-E; Hu, Li; Ma, Jun-Xian
Demodex caprae infests the hair follicles and sebaceous glands of goats worldwide, which not only seriously impairs goat farming, but also causes a big economic loss. However, there are few reports on the DNA level of D. caprae. To reveal the taxonomic position of D. caprae within the genus Demodex, the present study conducted phylogenetic analysis of D. caprae based on mt16S rDNA sequence data. D. caprae adults and eggs were obtained from a skin nodule of the goat suffering demodicidosis. The mt16S rDNA sequences of individual mite were amplified using specific primers, and then cloned, sequenced, and aligned. The sequence divergence, genetic distance, and transition/transversion rate were computed, and the phylogenetic trees in Demodex were reconstructed. Results revealed the 339-bp partial sequences of six D. caprae isolates were obtained, and the sequence identity was 100% among isolates. The pairwise divergences between D. caprae and Demodex canis or Demodex folliculorum or Demodex brevis were 22.2-24.0%, 24.0-24.9%, and 22.9-23.2%, respectively. The corresponding average genetic distances were 2.840, 2.926, and 2.665, and the average transition/transversion rates were 0.70, 0.55, and 0.54, respectively. The divergences, genetic distances, and transition/transversion rates of D. caprae versus the other three species all reached interspecies level. The five phylogenetic trees all presented that D. caprae clustered with D. brevis first, and then with D. canis, D. folliculorum, and Demodex injai in sequence. In conclusion, D. caprae is an independent species, and it is closer to D. brevis than to D. canis, D. folliculorum, or D. injai.
Yang, Kiwoung; Robin, Arif Hasan Khan; Yi, Go-Eun; Lee, Jonghoon; Chung, Mi-Young; Yang, Tae-Jin; Nou, Ill-Sup
Ribosomal DNA (rDNA) of plants is present in high copy number and shows variation between and within species in the length of the intergenic spacer (IGS). The 45S rDNA of flowering plants includes the 5.8S, 18S and 25S rDNA genes, the internal transcribed spacer (ITS1 and ITS2), and the intergenic spacer 45S-IGS (25S-18S). This study identified six different types of 45S-IGS, A to F, which at 363 bp, 1121 bp, 1717 bp, 1969 bp, 2036 bp and 2111 bp in length, respectively, were much shorter than the reported reference IGS sequences in B. oleracea var. alboglabra. The shortest two IGS types, A and B, lacked the transcription initiation site, non-transcribed spacer, and external transcribed spacer. Functional behavior of those two IGS types in relation to rRNA synthesis is a subject of further investigation. The other four IGSs had subtle variations in the transcription termination site, guanine-cytosine (GC) content, and number of tandem repeats, but the external transcribed spacers of these four IGSs were quite similar in length. The 45S IGSs were found to follow Mendelian inheritance in a population of 15 F1s and their 30 inbred parental lines, which suggests that these sequences could be useful for development of new breeding tools. In addition, this study represents the first report of intra-specific (within subspecies) variation of the 45S IGS in B. oleracea. PMID:26633391
Peng, Xingxing; Zhang, Zaili; Zhao, Ziling; Jia, Xiaoshan
Microorganisms able to rapidly degrade tetrabromobisphenol A (TBBPA) were domesticated in an anaerobic reactor and added to gradually increased concentrations of TBBPA. After 240 days of domestication, the degradation rate reached 96.0% in cultivated batch experiments lasting 20 days. The optimum cultivating temperature and pH were 30°C and 7.0. The bacterial community's composition and diversity in the reactor was studied by comparative analysis with 16S ribosomal DNA clone libraries. Amplified rDNA restriction analysis of 200 clones from the library indicate that the rDNA richness was high (Coverage C 99.5%) and that evenness was not high (Shannon-Weaver index 2.42). Phylogenetic analysis of 63 bacterial sequences from the reactor libraries demonstrated the presence of Betaproteobacteria (33.1%), Gammaproteobacteria (18.7%), Bacteroidetes (13.9%), Firmicutes (11.4%), Chloroflexi (3.6%), Actinobacteria (0.6%), the candidate division TM7 (4.2%) and other unknown, uncultured bacterial groups (14.5%). Comamonas, Achromobacter, Pseudomonas and Flavobacterium were the dominant types.
Liu, Guo-Hua; Yan, Hong-Bin; Otranto, Domenico; Wang, Xing-Ye; Zhao, Guang-Hui; Jia, Wan-Zhong; Zhu, Xing-Quan
Lancet flukes parasitize the bile ducts and gall bladder of a range of mammals, including humans, causing dicrocoeliosis. In the present study, we sequenced and characterized the complete mitochondrial (mt) genomes as well as the first and second internal transcribed spacers (ITS-1 and ITS-2=ITS) of nuclear ribosomal DNA (rDNA) of two lancet flukes, Dicrocoelium chinensis and D. dendriticum. Sequence comparison of a conserved mt gene and nuclear rDNA sequences among multiple individual lancet flukes revealed substantial nucleotide differences between the species but limited sequence variation within each of them. Phylogenetic analysis of the concatenated amino acid and multiple mt rrnS sequences using Bayesian inference supported the separation of D. chinensis and D. dendriticum into two distinct species-specific clades. Results of the present study support the proposal that D. dendriticum and D. chinensis represent two distinct lancet flukes. While providing the first mt genomes from members of the superfamily Plagiorchioidea, the novel mt markers described herein will be useful for further studies of the diagnosis, epidemiology and systematics of the lancet flukes and other trematodes of human and animal health significance.
Porter, Teresita M.; Shokralla, Shadi; Baird, Donald; Golding, G. Brian; Hajibabaei, Mehrdad
Though the use of metagenomic methods to sample below-ground fungal communities is common, the use of similar methods to sample plants from their underground structures is not. In this study we use high throughput sequencing of the ribulose-bisphosphate carboxylase large subunit (rbcL) plastid marker to study the plant community as well as the internal transcribed spacer and large subunit ribosomal DNA (rDNA) markers to investigate the fungal community from two wetland sites. Observed community richness and composition varied by marker. The two rDNA markers detected complementary sets of fungal taxa and total fungal composition clustered according to primer rather than by site. The composition of the most abundant plants, however, clustered according to sites as expected. We suggest that future studies consider using multiple genetic markers, ideally generated from different primer sets, to detect a more taxonomically diverse suite of taxa compared with what can be detected by any single marker alone. Conclusions drawn from the presence of even the most frequently observed taxa should be made with caution without corroborating lines of evidence. PMID:26731732
Dawid, I B; Rebbert, M L
Ribosomal RNA genes interrupted by type 1 insertions of 1 kb and 0.5 kb have been sequenced through the insertion region and compared with an uninterrupted gene. The 0.5 kb insertion is flanked by a duplication of a 14 bp segment that is present once in the uninterrupted gene; the 1 kb insertion is flanked by a duplication of 11 of these 14 bp. Short insertions are identical in their entire length to downstream regions of long insertions. No internal repeats occur in the insertion. The presence of target site duplications suggests that type 1 insertions arose by the introduction of transposable elements into rDNA. Short sequence homologies between the upstream ends of the insertions and the 28S' boundaries of the rRNA coding region suggest that short type 1 insertions may have arisen by recombination from longer insertions. We have sequenced both boundaries of two molecules containing type 2 insertions and the upstream boundary of a third; the points of interruption at the upstream boundary (28S' site) differ from each other in steps of 2 bp. Between the boundary in the 0.5 kb type 1 insertion and the type 2 boundaries there are distances of 74, 76, and 78 bp. At the downstream boundary (28S'' site) the two sequenced type 2 insertions are identical. The rRNA coding region of one molecule extends across the insertion without deletion or duplication, but a 2 bp deletion in the RNA coding region is present in the second molecule. Stretches of 13 or 22 adenine residues occur at the downstream (28S'') end of the two type 2 insertions.
Li, Kunpeng; Wang, Huaisong; Wang, Jiming; Sun, Jianying; Li, Zongyun; Han, Yonghua
The 5S and 45S rDNA sites are useful chromosome landmarks and can provide valuable information about karyotype evolution and species interrelationships. In this study, we employed fluorescence in situ hybridization (FISH) to determine the number and chromosomal location of 5S and 45S rDNA loci in 8 diploid Cucumis species. Two oligonucleotide painting probes specific for the rDNA-bearing chromosomes in C. melo were hybridized to other Cucumis species in order to investigate the homeologies among the rDNA-carrying chromosomes in Cucumis species. The analyzed diploid species showed 3 types of rDNA distribution patterns, which provided clear cytogenetic evidence on the divergence between C. melo and wild diploid African Cucumis species. The present results not only show species interrelationships in the genus Cucumis, but the rDNA FISH patterns can also be used as cytological markers for the discrimination of closely related species. The data will be helpful for breeders to choose the most suitable species from various wild species for improvement of cultivated melon.
Allaby, R G; Brown, T A
We have used network analysis to study gene sequences of the Triticum and Aegilops 5S rDNA arrays, as well as the spacers of the 5S-DNA-A1 and 5S-DNA-2 loci. Network analysis describes relationships between 5S rDNA sequences in a more realistic fashion than conventional tree building because it makes fewer assumptions about the direction of evolution, the extent of sexual isolation, and the pattern of ancestry and descent. The networks show that the 5S rDNA sequences of Triticum and Aegilops species are related in a reticulate manner around principal nodal sequences. The spacer networks have multiple principal nodes of considerable antiquity but the gene network has just one principal node, corresponding to the correct gene sequence. The networks enable orthologous groups of spacer sequences to be identified. When orthologs are compared it is seen that the patterns of intra- and interspecific diversity are similar for both genes and spacers. We propose that 5S rDNA arrays combine sequence conservation with a large store of mutant variations, the number of correct gene copies within an array being the result of neutral processes that act on gene and spacer regions together. PMID:11238418
Baty, G; Lanotte, P; Hocqueloux, L; Prazuck, T; Bret, L; Romano, M; Mereghetti, L
We report the case of a 55 year-old man presenting with a double aortic and mitral endocarditis for which resected valve culture was repeatedly negative. Specific PCR made on valves because of highly positive blood tests for Bartonella henselae remained negative. A molecular approach was made with 16S rDNA PCR, followed by sequencing. Bartonella quintana was identified as the etiology of endocarditis. B. quintana, "fastidious" bacteria, even if hard to identify in a laboratory, is often reported as a blood culture negative endocarditis (BCNE) agent. Molecular biology methods have strongly improved the diagnosis of BCNE. We propose a review of the literature focusing on the interest of broad-spectrum PCR on valve for the etiological diagnosis of BCNE.
Pourshafie, M; Vahdani, P; Popoff, M
In this study, the application of amplified rDNA restriction analysis (ARDRA) for characterizing Clostridium botulinum toxinotype A strains isolated from individuals with botulism was evaluated. Ten restriction enzymes were tested for their suitability in ARDRA as a typing method and HhaI was selected for the best outcome. Analysis of HhaI restriction profiles of the amplified products divided C. botulinum isolates into three clusters. Non-toxigenic Clostridium sporogenes strains showed an ARDRA restriction pattern that was distinct from those observed for C. botulinum. The successful use of ARDRA for subdivision of C. botulinum in this study confirmed that this technique is a powerful method for typing of C. botulinum toxinotype A clonal diversity. In addition, it is rapid, sensitive and simple.
Nava, Santiago; Venzal, José M; Labruna, Marcelo B; Mastropaolo, Mariano; González, Enrique M; Mangold, Atilio J; Guglielmone, Alberto A
We supply information about hosts and distribution of Amblyomma dubitatum. In addition, we carry out an analysis of genetic divergence among specimens of A. dubitatum from different localities and with respect to other Neotropical Amblyomma species, using sequences of 16S rDNA gene. Although specimens of A. dubitatum were collected on several mammal species as cattle horse, Tapirus terrestris, Mazama gouazoubira, Tayassu pecari, Sus scrofa, Cerdocyon thous, Myocastor coypus, Allouata caraya, Glossophaga soricina and man, most records of immature and adult stages of A. dubitatum were made on Hydrochoerus hydrochaeris, making this rodent the principal host for all parasitic stages of this ticks. Cricetidae rodents (Lundomys molitor, Scapteromys tumidus), opossums (Didelphis albiventris) and vizcacha (Lagostomus maximus) also were recorded as hosts for immature stages. All findings of A. dubitatum correspond to localities of Argentina, Brazil, Paraguay and Uruguay, and they were concentrated in the Biogeographical provinces of Pampa, Chaco, Cerrado, Brazilian Atlantic Forest, Parana Forest and Araucaria angustifolia Forest. The distribution of A. dubitatum is narrower than that of its principal host, therefore environmental variables rather than hosts determine the distributional ranges of this tick. The intraspecific genetic divergence among 16S rDNA sequences of A. dubitatum ticks collected in different localities from Argentina, Brazil and Uruguay was in all cases lower than 0.8%, whereas the differences with the remaining Amblyomma species included in the analysis were always bigger than 6.8%. Thus, the taxonomic status of A. dubitatum along its distribution appears to be certain at the specific level.
Aktas, Münir; Bendele, Kylie G; Altay, Kürsat; Dumanli, Nazir; Tsuji, Masayoshi; Holman, Patricia J
The genomic region spanning the two ribosomal RNA internal transcribed spacers (ITS1 and ITS2) and the 5.8S rRNA gene was cloned and sequenced from sixteen Theileria isolates. Each Theileria species possessed ITS1 and ITS2 of unique size(s) and species specific nucleotide sequences. Varying degrees of ITS1 and ITS2 intra- and inter-species sequence polymorphism were found among ruminant Theileria species. The spacers were most polymorphic in the agent of tropical theileriosis, Theileria annulata, and were more conserved in two benign species, Theileria buffeli and Theileria sergenti Chitose. Phylogenetic analysis of the rDNA ITS1-5.8S rRNA gene-ITS2 region clearly separated each taxon, placing them in three clusters. One held T. annulata, Theileria parva, and Theileria mutans, with the latter two most closely related. The second held T. sergenti Ikeda, T. sergenti Chitose, and T. buffeli, with the latter two most closely related. The third cluster held the Theileria ovis isolates.
Zhao, Ya-E; Wang, Zheng-Hang; Xu, Yang; Wu, Li-Ping; Hu, Li
According to base pairing, the rRNA folds into corresponding secondary structures, which contain additional phylogenetic information. On the basis of sequencing for complete rDNA sequences (18S, ITS1, 5.8S, ITS2 and 28S rDNA) of Demodex, we predicted the secondary structure of the complete rDNA sequence (18S, 5.8S, and 28S rDNA) of Demodex folliculorum, which was in concordance with that of the main arthropod lineages in past studies. And together with the sequence data from GenBank, we also predicted the secondary structures of divergent domains in SSU rRNA of 51 species and in LSU rRNA of 43 species from four superfamilies in Acari (Cheyletoidea, Tetranychoidea, Analgoidea and Ixodoidea). The multiple alignment among the four superfamilies in Acari showed that, insertions from Tetranychoidea SSU rRNA formed two newly proposed helixes, and helix c3-2b of LSU rRNA was absent in Demodex (Cheyletoidea) taxa. Generally speaking, LSU rRNA presented more remarkable differences than SSU rRNA did, mainly in D2, D3, D5, D7a, D7b, D8 and D10.
Ihara, Motomasa; Tseng, Hung; Schultz, Richard M.
Ribosomal DNA (rDNA) is not composed of multiple copies of identical transcription units, as commonly believed, but rather of at least seven rDNA variant subtypes that are expressed in somatic cells. This finding raises the possibility that ribosome function may be modulated as proposed by the ribosome filter hypothesis. We report here that mouse oocytes and preimplantation embryos express all the rDNA variants except variant V and that there is no marked developmental change in the qualitative pattern of variant expression. The maternal and embryonic ribosome pools are therefore quite similar, minimizing the likelihood that developmental changes in composition of the ribosome population are critical for preimplantation development. PMID:21209414
Pope, Bernard J; Mahmood, Khalid; Jung, Chol-Hee; Park, Daniel J
DNA breakage arises during a variety of biological processes, including transcription, replication and genome rearrangements. In the context of disease, extensive fragmentation of DNA has been described in cancer cells and during early stages of neurodegeneration (Stephens et al., 2011 Stephens et al. (2011) ; Blondet et al., 2001 Blondet et al. (2001) ). Stults et al. (2009) Stults et al. (2009)  reported that human rDNA gene clusters are hotspots for recombination and that rDNA restructuring is among the most common chromosomal alterations in adult solid tumours. As such, analysis of rDNA regions is likely to have significant prognostic and predictive value, clinically. Tchurikov et al. (2015a, 2016) Tchurikov et al. (2015a, 2016) ,  have made major advances in this direction, reporting that sites of human genome double-strand breaks (DSBs) occur frequently at sites in rDNA that are tightly linked with active transcription - the authors used a RAFT (rapid amplification of forum termini) protocol that selects for blunt-ended sites. They reported the relative frequency of these rDNA DSBs within defined co-ordinate 'windows' of varying size and made these data (as well as the relevant 'raw' sequencing information) available to the public (Tchurikov et al., 2015b). Assay designs targeting rDNA DSB hotspots will benefit greatly from the publication of break sites at greater resolution. Here, we re-analyse public RAFT data and make available rDNA DSB co-ordinates to the single-nucleotide level.
Kobayashi, Satoru; Taki, Tomohiko; Nagoshi, Hisao; Chinen, Yoshiaki; Yokokawa, Yuichi; Kanegane, Hirokazu; Matsumoto, Yosuke; Kuroda, Junya; Horiike, Shigeo; Nishida, Kazuhiro; Taniwaki, Masafumi
Fusion genes are frequently observed in hematologic malignancies and soft tissue sarcomas, and are usually associated with chromosome abnormalities. Many of these fusion genes create in-frame fusion transcripts that result in the production of fusion proteins, and some of which aid tumorigenesis. These fusion proteins are often associated with disease phenotype and clinical outcome, and act as markers for minimal residual disease and indicators of therapeutic targets. Here, we identified the 28S ribosomal DNA (RN28S1) gene as a novel fusion partner of the B-cell leukemia/lymphoma 11B gene (BCL11B), the immunoglobulin κ variable 3-20 gene (IGKV3-20) and the component of oligomeric Golgi complex 1 gene (COG1) in hematologic malignancies. The RN28S1-BCL11B fusion transcript was identified in a case with mixed-lineage (T/myeloid) acute leukemia having t(6;14)(q25;q32) by cDNA bubble PCR using BCL11B primers; however, the gene fused to BCL11B on 14q32 was not on 6q25. IGKV3-20-RN28S1 and COG1-RN28S1 fusion transcripts were identified in the Burkitt lymphoma cell line HBL-5, and the multiple myeloma cell line KMS-18. RN28S1 would not translate, and the breakpoints in partner genes of RN28S1 were within the coding exons, suggesting that disruption of fusion partners by fusion to RN28S1 is the possible mechanism of tumorigenesis. Although further analysis is needed to elucidate the mechanism(s) through which these RN28S1-related fusions play roles in tumorigenesis, our findings provide important insights into the role of rDNA function in human genomic architecture and tumorigenesis.
Lan, Hong; Chen, Chun-Li; Miao, Yin; Yu, Chang-Xiu; Guo, Wen-Wu; Xu, Qiang; Deng, Xiu-Xin
Citrus sinensis chromosomes present a morphological differentiation of bands after staining by the fluorochromes CMA and DAPI, but there is still little information on its chromosomal characteristics. In this study, the chromosomes in ‘Valencia’ C. sinensis were analyzed by fluorescence in situ hybridization (FISH) using telomere DNA and the 45S rDNA gene as probes combining CMA/DAPI staining, which showed that there were two fragile sites in sweet orange chromosomes co-localizing at distended 45S rDNA regions, one proximally locating on B-type chromosome and the other subterminally locating on D-type chromosome. While the chromosomal CMA banding and 45S rDNA FISH mapping in the doubled haploid line of ‘Valencia’ C. sinensis indicated six 45S rDNA regions, four were identified as fragile sites as doubled comparing its parental line, which confirmed the cytological heterozygosity and chromosomal heteromorphisms in sweet orange. Furthermore, Ag-NOR identified two distended 45S rDNA regions to be active nucleolar organizing regions (NORs) in diploid ‘Valencia’ C. sinensis. The occurrence of quadrivalent in meiosis of pollen mother cells (PMCs) in ‘Valencia’ sweet orange further confirmed it was a chromosomal reciprocal translocation line. We speculated this chromosome translocation was probably related to fragile sites. Our data provide insights into the chromosomal characteristics of the fragile sites in ‘Valencia’ sweet orange and are expected to facilitate the further investigation of the possible functions of fragile sites. PMID:26977938
Dolven, Jane K.; Ose, Randi F.; Klaveness, Dag; Kristensen, Tom; Bjørklund, Kjell R.; Shalchian-Tabrizi, Kamran
Radiolarians are marine planktonic protists that belong to the eukaryote supergroup Rhizaria together with Foraminifera and Cercozoa. Radiolaria has traditionally been divided into four main groups based on morphological characters; i.e. Polycystina, Acantharia, Nassellaria and Phaeodaria. But recent 18S rDNA phylogenies have shown that Phaeodaria belongs within Cerocozoa, and that the previously heliozoan group Taxopodida should be included in Radiolaria. 18S rDNA phylogenies have not yet resolved the sister relationship between the main Radiolaria groups, but nevertheless suggests that Spumellaria, and thereby also Polycystina, are polyphyletic. Very few sequences other than 18S rDNA have so far been generated from radiolarian cells, mostly due to the fact that Radiolaria has been impossible to cultivate and single cell PCR has been hampered by low success rate. Here we have therefore investigated the mutual evolutionary relationship of the main radiolarian groups by using the novel approach of combining single cell whole genome amplification with targeted PCR amplification of the 18S and 28S rDNA genes. Combined 18S and 28S phylogeny of sequences obtained from single cells shows that Radiolaria is divided into two main lineages: Polycystina (Spumellaria+Nassellaria) and Spasmaria (Acantharia+Taxopodida). Further we show with high support that Foraminifera groups within Radiolaria supporting the Retaria hypothesis. PMID:21853146
Pérez-González, César E; Eickbush, Thomas H
R1 and R2 elements are non-LTR retrotransposons that insert specifically into the 28S rRNA genes of arthropods. The process of concerted evolution of the rDNA locus should give rise to rapid turnover of these mobile elements compared to elements that insert at sites throughout a genome. To estimate the rate of R1 and R2 turnover we have examined the insertion of new elements and elimination of old elements in the Harwich mutation accumulation lines of Drosophila melanogaster, a set of inbred lines maintained for >350 generations. Nearly 300 new insertion and elimination events were observed in the 19 Harwich lines. The retrotransposition rate for R1 was 18 times higher than the retrotransposition rate for R2. Both rates were within the range previously found for retrotransposons that insert outside the rDNA loci in D. melanogaster. The elimination rates of R1 and R2 from the rDNA locus were similar to each other but over two orders of magnitude higher than that found for other retrotransposons. The high rates of R1 and R2 elimination from the rDNA locus confirm that these elements must maintain relatively high rates of retrotransposition to ensure their continued presence in this locus. PMID:12399390
Köhsler, Martina; Leitner, Brigitte; Blaschitz, Marion; Michel, Rolf; Aspöck, Horst; Walochnik, Julia
The subgenus classification of the ubiquitously spread and potentially pathogenic acanthamoebae still poses a great challenge. Fifteen 18S rDNA sequence types (T1-T15) have been established, but the vast majority of isolates fall into sequence type T4, and so far, there is no means to reliably differentiate within T4. In this study, the first internal transcribed spacer (ITS1), a more variable region than the 18S rRNA gene, was sequenced, and the sequences of 15 different Acanthamoeba isolates were compared to reveal if ITS1 sequence variability correlates with 18S rDNA sequence typing and if the ITS1 sequencing allows a differentiation within T4. It was shown that the variability in ITS1 is tenfold higher than in the 18S rDNA, and that ITS1 clusters correlate with the 18S rDNA clusters and thus corroborate the Acanthamoeba sequence type system. Moreover, high sequence dissimilarities and distinctive microsatellite patterns could enable a more detailed differentiation within T4.
Sochorová, Jana; Coriton, Olivier; Kuderová, Alena; Lunerová, Jana; Chèvre, Anne-Marie; Kovařík, Aleš
Background and aims Brassica napus (AACC, 2n = 38, oilseed rape) is a relatively recent allotetraploid species derived from the putative progenitor diploid species Brassica rapa (AA, 2n = 20) and Brassica oleracea (CC, 2n = 18). To determine the influence of intensive breeding conditions on the evolution of its genome, we analysed structure and copy number of rDNA in 21 cultivars of B. napus, representative of genetic diversity. Methods We used next-generation sequencing genomic approaches, Southern blot hybridization, expression analysis and fluorescence in situ hybridization (FISH). Subgenome-specific sequences derived from rDNA intergenic spacers (IGS) were used as probes for identification of loci composition on chromosomes. Key Results Most B. napus cultivars (18/21, 86 %) had more A-genome than C-genome rDNA copies. Three cultivars analysed by FISH (‘Darmor’, ‘Yudal’ and ‘Asparagus kale’) harboured the same number (12 per diploid set) of loci. In B. napus ‘Darmor’, the A-genome-specific rDNA probe hybridized to all 12 rDNA loci (eight on the A-genome and four on the C-genome) while the C-genome-specific probe showed weak signals on the C-genome loci only. Deep sequencing revealed high homogeneity of arrays suggesting that the C-genome genes were largely overwritten by the A-genome variants in B. napus ‘Darmor’. In contrast, B. napus ‘Yudal’ showed a lack of gene conversion evidenced by additive inheritance of progenitor rDNA variants and highly localized hybridization signals of subgenome-specific probes on chromosomes. Brassica napus ‘Asparagus kale’ showed an intermediate pattern to ‘Darmor’ and ‘Yudal’. At the expression level, most cultivars (95 %) exhibited stable A-genome nucleolar dominance while one cultivar (‘Norin 9’) showed co-dominance. Conclusions The B. napus cultivars differ in the degree and direction of rDNA homogenization. The prevalent direction of gene conversion (towards the A-genome) correlates
Fernández-Tajes, Juan; Méndez, Josefina
For a study of 5S ribosomal genes (rDNA) in the razor clam Ensis macha, the 5S rDNA region was amplified and sequenced. Two variants, so-called type I or short repeat (approximately 430 bp) and type II or long repeat (approximately 735 bp), appeared to be the main components of the 5S rDNA of this species. Their spacers differed markedly, both in length and nucleotide composition. The organization of the two variants was investigated by amplifying the genomic DNA with primers based on the sequence of the type I and type II spacers. PCR amplification products with primers EMLbF and EMSbR showed that the long and short repeats are associated within the same tandem array, suggesting an intermixed arrangement of both spacers. Nevertheless, amplifications carried out with inverse primers EMSinvF/R and EMLinvF/R revealed that some short and long repeats are contiguous in the same tandem array. This is the first report of the coexistence of two variable spacers in the same tandem array in bivalve mollusks.
Leander, Brian S; Clopton, Richard E; Keeling, Patrick J
Gregarines are thought to be deep-branching apicomplexans. Accordingly, a robust inference of gregarine phylogeny is crucial to any interpretation of apicomplexan evolution, but molecular sequences from gregarines are restricted to a small number of small-subunit (SSU) rDNA sequences from derived taxa. This work examines the usefulness of SSU rDNA and beta-tubulin sequences for inferring gregarine phylogeny. SSU rRNA genes from Lecudina (Mingazzini) sp., Monocystis agilis Stein, Leidyana migrator Clopton and Gregarina polymorpha Dufour, as well as the beta-tubulin gene from Leidyana migrator, were sequenced. The results of phylogenetic analyses of alveolate taxa using both genes were consistent with an early origin of gregarines and the putative 'sister' relationship between gregarines and Cryptosporidium, but neither phylogeny was strongly supported. In addition, two SSU rDNA sequences from unidentified marine eukaryotes were found to branch among the gregarines: one was a sequence derived from the haemolymph parasite of the giant clam, Tridacna crocea, and the other was a sequence misattributed to the foraminiferan Ammonium beccarii. In all of our analyses, the SSU rDNA sequence from Colpodella sp. clustered weakly with the apicomplexans, which is consistent with ultrastructural data. Altogether, the exact position of gregarines with respect to Cryptosporidium and other apicomplexans remains to be confirmed, but the congruence of SSU rDNA and beta-tubulin trees with one another and with morphological data does suggest that further sampling of molecular data will eventually put gregarine diversity into a phylogenetic context.
Molini, Barbara J.; Tantalo, Lauren C.; Sahi, Sharon K.; Rodriguez, Veronica I.; Brandt, Stephanie L.; Fernandez, Mark C.; Godornes, Charmie B.; Marra, Christina M.; Lukehart, Sheila A.
Background High rates of 23S rDNA mutations implicated in macrolide resistance have been identified in Treponema pallidum samples from syphilis patients in many countries. Nonetheless, some clinicians have been reluctant to abandon azithromycin as a treatment for syphilis, citing the lack of a causal association between these mutations and clinical evidence of drug resistance. Although azithromycin resistance has been demonstrated in vivo for the historical Street 14 strain, no recent T. pallidum isolates have been tested. We used the well-established rabbit model of syphilis to determine the in vivo efficacy of azithromycin against 23S rDNA mutant strains collected in 2004 to 2005 from patients with syphilis in Seattle, Wash. Methods Groups of 9 rabbits were each infected with a strain containing 23S rDNA mutation A2058G (strains UW074B, UW189B, UW391B) or A2059G (strains UW228B, UW254B, and UW330B), or with 1 wild type strain (Chicago, Bal 3, and Mexico A). After documentation of infection, 3 animals per strain were treated with azithromycin, 3 were treated with benzathine penicillin G, and 3 served as untreated control groups. Treatment efficacy was documented by darkfield microscopic evidence of T. pallidum, serological response, and rabbit infectivity test. Results Azithromycin uniformly failed to cure rabbits infected with strains harboring either 23S rDNA mutation, although benzathine penicillin G was effective. Infections caused by wild type strains were successfully treated by either azithromycin or benzathine penicillin G. Conclusions A macrolide resistant phenotype was demonstrated for all strains harboring a 23S rDNA mutation, demonstrating that either A2058G or A2059G mutation confers in vivo drug resistance. PMID:27513385
Zhu, X Q; Podolska, M; Liu, J S; Yu, H Q; Chen, H H; Lin, Z X; Luo, C B; Song, H Q; Lin, R Q
Using genetic markers defined previously in the second internal transcribed spacer (ITS-2) of nuclear ribosomal DNA (rDNA), isotopic, and non-isotopic polymerase-chain-reaction-coupled single-strand conformation polymorphism (SSCP) were utilized to identify each of three anisakid species [Anisakis simplex (s.l.), Contracaecum osculatum (s.l.), and Hysterothylacium aduncum] from different host species and geographical locations in Poland and Sweden. While subtle microheterogeneity was observed within each of Anisakis simplex (s.l.) and H. aduncum, distinct SSCP profiles were displayed for each of the three species, allowing identification and differentiation of the three taxa. Subsequent sequencing of the ITS-1 and ITS-2 rDNA revealed that A. simplex (s.l.) represented Anisakis simplex s.s. and Contracaecum osculatum (s.l.) represented C. osculatum C. Application of the non-isotopic SSCP assay of ITS-2 to larval anisakid samples from different hosts and geographical locations in China revealed three distinct SSCP profiles, one of which was consistent with that of A. simplex (s.l.), and the other two had different SSCP profiles from that of C. osculatum C and H. aduncum. Sequencing of the ITS-1 and ITS-2 rDNA for representative Chinese anisakid samples examined revealed three anisakid species in China, i.e., Anisakis typica, Anisakis pegreffii, and Hysterothylacium sp. These molecular tools will be useful for identification and investigation of the ecology of anisakid nematodes in China and elsewhere.
Romeralo, María; Escalante, Ricardo; Sastre, Leandro; Lado, Carlos
The variability and adaptability of the amoebae from the class Dictyosteliomycetes greatly complicate their systematics. The nucleotide sequences of the ribosomal internal transcribed spacers and the 5.8S ribosomal DNA gene have been determined for 28 isolates, and their utility to discriminate between different species and genera has been shown. PMID:17056743
Inácio, Vera; Rocheta, Margarida; Morais-Cecílio, Leonor
The 35S ribosomal DNA (rDNA) units, repeated in tandem at one or more chromosomal loci, are separated by an intergenic spacer (IGS) containing functional elements involved in the regulation of transcription of downstream rRNA genes. In the present work, we have compared the IGS molecular organizations in two divergent species of Fagaceae, Fagus sylvatica and Quercus suber, aiming to comprehend the evolution of the IGS sequences within the family. Self- and cross-hybridization FISH was done on representative species of the Fagaceae. The IGS length variability and the methylation level of 18 and 25S rRNA genes were assessed in representatives of three genera of this family: Fagus, Quercus and Castanea. The intergenic spacers in Beech and Cork Oak showed similar overall organizations comprising putative functional elements needed for rRNA gene activity and containing a non-transcribed spacer (NTS), a promoter region, and a 5'-external transcribed spacer. In the NTS: the sub-repeats structure in Beech is more organized than in Cork Oak, sharing some short motifs which results in the lowest sequence similarity of the entire IGS; the AT-rich region differed in both spacers by a GC-rich block inserted in Cork Oak. The 5'-ETS is the region with the higher similarity, having nonetheless different lengths. FISH with the NTS-5'-ETS revealed fainter signals in cross-hybridization in agreement with the divergence between genera. The diversity of IGS lengths revealed variants from ∼ 2 kb in Fagus, and Quercus up to 5.3 kb in Castanea, and a lack of correlation between the number of variants and the number of rDNA loci in several species. Methylation of 25S Bam HI site was confirmed in all species and detected for the first time in the 18S of Q. suber and Q. faginea. These results provide important clues for the evolutionary trends of the rDNA 25S-18S IGS in the Fagaceae family.
Yang, Qianqian; Zhao, Shuo; Kucerová, Zuzana; Stejskal, Václav; Opit, George; Qin, Meng; Cao, Yang; Li, Fujun; Li, Zhihong
Psocids are serious storage pests, and their control is hampered by the fact that different species respond differently to insecticides used for the control of stored-product insect pests. Additionally, psocids of genus Liposcelis that are commonly associated with stored-products are difficult to identify using morphological characteristics. The goal of this study was to validate molecular identification of stored-product psocids of genus Liposcelis based on 16S rDNA and cytochrome oxidase I (COI) DNA barcoding. Unidentified liposcelids (Liposcelis DK) imported from Denmark to China were compared with 14 population samples of seven common species (L. bostrychophila, L. brunnea, L. corrodens, L. decolor, L. entomophila, L. mendax, and L. paeta). The explored species (DK) liposcelids shared >98% sequence similarity for both the 16S rDNA and COI genes with the reference L. corrodens samples (98.32 and 98.94% for 16S rDNA and COI, respectively). A neighbor-joining tree revealed that the explored DK sample and the reference L. corrodens samples belong to the same clade. These molecular results were verified by morphological identification of DK specimens, facilitated by SEM microphotography. The DNA barcoding method and the neighbor-joining phylogenetic analyses indicated that both the 16S rDNA and COI genes were suitable for Liposcelis species identification. DNA barcoding has great potential for use in fast and accurate liposcelid identification.
Khaitová, L; Werlemark, G; Nybom, H; Kovarík, A
The polyploid species in Rosa section Caninae (2n=21, 28 or 35) are characterized by an unusual reproductive system known as odd (or asymmetric) meiosis. Only two chromosome sets form bivalents in meiosis, whereas the remaining chromosomes are transmitted as univalents through the female germline. Evolution of ribosomal rRNA genes (rDNA) does not seem to be significantly affected by interlocus homogenization in dogroses. As a consequence, most species contain several rDNA families falling into two main clades (beta and gamma) thought to be differentially distributed between bivalent and univalent chromosomes, respectively. Here, we have investigated expression of rRNA gene families in five pentaploid species (R. canina, R. rubiginosa, R. dumalis, R. sherardii and R. caesia, 2n=35) and in one tetraploid (R. mollis, 2n=28). Using extensive sequencing of ITS clones and cleaved amplified polymorphism sequence (CAPS) analysis, we found that the beta-family was constitutively expressed in all species. However, there was large variation in the expression patterns of families constituting the gamma-clade. In addition, a single family can be active in one species, whereas silenced in another. The data show that the families on bivalent-forming chromosomes dominate rDNA expression in all dogrose species. We hypothesize that genes on bivalent genomes are stably expressed, whereas those on univalent genomes undergo variable levels of epigenetic silencing. Nonetheless, mosaic expression of univalent genomes could contribute to phenotypic variation between the species.
Alix, J H; Guérin, M F
To determine whether the biogenesis of ribosomes in Escherichia coli is the result of the self-assembly of their different constituents or involves the participation of additional factors, we have studied the influence of a chaperone, the product of the gene dnaK, on ribosome assembly in vivo. Using three thermosensitive (ts) mutants carrying the mutations dnaK756-ts, dnaK25-ts, and dnaK103-ts, we have observed the accumulation at nonpermissive temperature (45 degrees C) of ribosomal particles with different sedimentation constants--namely, 45S, 35S, and 25S along with the normal 30S and 50S ribosomal subunits. This is the result of a defect not in thermostability but in ribosome assembly at the nonpermissive temperature. These abnormal ribosomal particles are rescued if the mutant cells are returned to 30 degrees C. Thus, the product of the dnaK gene is implicated in ribosome biogenesis at high temperature. PMID:8105482
Triploblastic relationships with emphasis on the acoelomates and the position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognatha: a combined approach of 18S rDNA sequences and morphology.
Giribet, G; Distel, D L; Polz, M; Sterrer, W; Wheeler, W C
Triploblastic relationships were examined in the light of molecular and morphological evidence. Representatives for all triploblastic "phyla" (except Loricifera) were represented by both sources of phylogenetic data. The 18S ribosomal (rDNA) sequence data for 145 terminal taxa and 276 morphological characters coded for 36 supraspecific taxa were combined in a total evidence regime to determine the most consistent picture of triploblastic relationships for these data. Only triploblastic taxa are used to avoid rooting with distant outgroups, which seems to happen because of the extreme distance that separates diploblastic from triploblastic taxa according to the 18S rDNA data. Multiple phylogenetic analyses performed with variable analysis parameters yield largely inconsistent results for certain groups such as Chaetognatha, Acoela, and Nemertodermatida. A normalized incongruence length metric is used to assay the relative merit of the multiple analyses. The combined analysis having the least character incongruence yields the following scheme of relationships of four main clades: (1) Deuterostomia [((Echinodermata + Enteropneusta) (Cephalochordata (Urochordata + Vertebrata)))]; (2) Ecdysozoa [(((Priapulida + Kinorhyncha) (Nematoda + Nematomorpha)) ((Onychophora + Tardigrada) Arthropoda))]; (3) Trochozoa [((Phoronida + Brachiopoda) (Entoprocta (Nemertea (Sipuncula (Mollusca (Pogonophora (Echiura + Annelida)))))))]; and (4) Platyzoa [((Gnathostomulida (Cycliophora + Syndermata)) (Gastrotricha + Plathelminthes))]. Chaetognatha, Nemertodermatida, and Bryozoa cannot be assigned to any one of these four groups. For the first time, a data analysis recognizes a clade of acoelomates, the Platyzoa (sensu Cavalier-Smith, Biol. Rev. 73:203-266, 1998). Other relationships that corroborate some morphological analyses are the existence of a clade that groups Gnathostomulida + Syndermata (= Gnathifera), which is expanded to include the enigmatic phylum Cycliophora, as sister group
Boutte, Julien; Aliaga, Benoît; Lima, Oscar; Ferreira de Carvalho, Julie; Ainouche, Abdelkader; Macas, Jiri; Rousseau-Gueutin, Mathieu; Coriton, Olivier; Ainouche, Malika; Salmon, Armel
Gene and whole-genome duplications are widespread in plant nuclear genomes, resulting in sequence heterogeneity. Identification of duplicated genes may be particularly challenging in highly redundant genomes, especially when there are no diploid parents as a reference. Here, we developed a pipeline to detect the different copies in the ribosomal RNA gene family in the hexaploid grass Spartina maritima from next-generation sequencing (Roche-454) reads. The heterogeneity of the different domains of the highly repeated 45S unit was explored by identifying single nucleotide polymorphisms (SNPs) and assembling reads based on shared polymorphisms. SNPs were validated using comparisons with Illumina sequence data sets and by cloning and Sanger (re)sequencing. Using this approach, 29 validated polymorphisms and 11 validated haplotypes were reported (out of 34 and 20, respectively, that were initially predicted by our program). The rDNA domains of S. maritima have similar lengths as those found in other Poaceae, apart from the 5′-ETS, which is approximately two-times longer in S. maritima. Sequence homogeneity was encountered in coding regions and both internal transcribed spacers (ITS), whereas high intragenomic variability was detected in the intergenic spacer (IGS) and the external transcribed spacer (ETS). Molecular cytogenetic analysis by fluorescent in situ hybridization (FISH) revealed the presence of one pair of 45S rDNA signals on the chromosomes of S. maritima instead of three expected pairs for a hexaploid genome, indicating loss of duplicated homeologous loci through the diploidization process. The procedure developed here may be used at any ploidy level and using different sequencing technologies. PMID:26530424
Alfreider, Albin; Vogt, Carsten; Babel, Wolfgang
A molecular approach based on the construction of 16S ribosomal DNA clone libraries was used to investigate the microbial diversity of an underground in situ reactor system filled with the original aquifer sediments. After chemical steady state was reached in the monochlorobenzene concentration between the original inflowing groundwater and the reactor outflow, samples from different reactor locations and from inflowing and outflowing groundwater were taken for DNA extraction. Small-subunit rRNA genes were PCR-amplified with primers specific for Bacteria, subsequently cloned and screened for variation by restriction fragment length polymorphism (RFLP). A total of 87 bacterial 16S rDNA genes were sequenced and subjected to phylogenetic analysis. The original groundwater was found to be dominated by a bacterial consortium affiliated with various members of the class of Proteobacteria, by phylotypes not affiliated with currently recognized bacterial phyla, and also by sporulating and non-sporulating sulfate-reducing bacteria. The most occurring clone types obtained from the sediment samples of the reactor were related to the beta-Proteobacteria, dominated by sequences almost identical to the widespread bacterium Alcaligenes faecalis, to low G+C gram-positive bacteria and to Acidithiobacillus ferrooxidans (formerly Thiobacillus ferrooxidans) within the gamma subclass of Proteobacteria in the upper reactor sector. Although bacterial phylotypes originating from the groundwater outflow of the reactors also grouped within different subdivisions of Proteobacteria and low G+C gram-positive bacteria, most of the 16S rDNA sequences were not associated with the sequence types observed in the reactor samples. Our results suggest that the different environments were inhabited by distinct microbial communities in respect to their taxonomic diversity, particular pronounced between sediment attached microbial communities from the reactor samples and free-living bacteria from the
Hiergeist, Andreas; Reischl, Udo; Gessner, Andrè
The composition of human as well as animal microbiota has increasingly gained in interest since metabolites and structural components of endogenous microorganisms fundamentally influence all aspects of host physiology. Since many of the bacteria are still unculturable, molecular techniques such as high-throughput sequencing have dramatically increased our knowledge of microbial communities. The majority of microbiome studies published thus far are based on bacterial 16S ribosomal RNA (rRNA) gene sequencing, so that they can, at least in principle, be compared to determine the role of the microbiome composition for host metabolism and physiology, developmental processes, as well as different diseases. However, differences in DNA preparation and purification, 16S rDNA PCR amplification, sequencing procedures and platforms, as well as bioinformatic analysis and quality control measures may strongly affect the microbiome composition results obtained in different laboratories. To systematically evaluate the comparability of results and identify the most influential methodological factors affecting these differences, identical human stool sample replicates spiked with quantified marker bacteria, and their subsequent DNA sequences were analyzed by nine different centers in an external quality assessment (EQA). While high intra-center reproducibility was observed in repetitive tests, significant inter-center differences of reported microbiota composition were obtained. All steps of the complex analysis workflow significantly influenced microbiome profiles, but the magnitude of variation caused by PCR primers for 16S rDNA amplification was clearly the largest. In order to advance microbiome research to a more standardized and routine medical diagnostic procedure, it is essential to establish uniform standard operating procedures throughout laboratories and to initiate regular proficiency testing.
Daxboeck, Florian; Dornbusch, Hans Jürgen; Krause, Robert; Assadian, Ojan; Wenisch, Christoph
A small but significant proportion of blood cultures processed by the BACTEC 9000 series systems is signaled positive, while subsequent Gram's stain and culture on solid media yield no pathogens. In this study, 15 "false-positive" vials (7 aerobes, 8 anaerobes) from 15 patients were investigated for the presence of bacteria and fungi by eubacterial 16S rDNA and panfungal 18S rDNA amplification, respectively. All samples turned out negative by both methods. Most patients (7) had neutropenia, which does not support the theory that high leukocyte counts enhance the generation of false-positive results. In conclusion, the results of this study indicate that false-negative results generated by the BACTEC 9000 series are inherent to the automated detection and not due to the growth of fastidious organisms.
Jenkins, M C; Miska, K; Klopp, S
A method was developed to recover Eimeria spp. oocysts directly from poultry litter and determine which species of Eimeria were present using polymerase chain reaction (PCR) based on the ITS1 rDNA sequence. The species composition of Eimeria oocysts was also compared before and after propagation in susceptible chickens to determine if the relative proportion of each species changed after expansion. In samples from two broiler operations, ITS1-PCR was able to detect Eimeria spp. oocysts recovered from litter, with Eimeria acervulina, Eimeria maxima, and Eimeria praecox being the predominant species present therein. Although Eimeria tenella was found in one sample, the other species--Eimeria brunetti, Eimeria necatrix, and Eimeria mitis-were not detected. The species composition as determined by ITS1-PCR did not appear to appreciably alter after expansion in susceptible chickens. The described method represents a rapid means for determining the major Eimeria species in a poultry operation and may be helpful in choosing a particular live oocyst vaccine formulation to protect chickens against coccidiosis.
Mendlová, Monika; Pariselle, Antoine; Vyskočilová, Martina; Simková, Andrea
The African freshwater fish of Cichlidae are parasitized by five genera of monogeneans belonging to Dactylogyridea. Ectoparasitic Scutogyrus, Onchobdella, and the highly diversified Cichlidogyrus represent three genera located on the gills, while the endoparasitic Enterogyrus and Urogyrus are located in the stomach and the urinary bladder, respectively. Representatives of four dactylogyridean genera (except for Urogyrus) were collected from seven cichlid species in West Africa. The aim of this study was to investigate the phylogenetic relationships between ectoparasitic and endoparasitic dactylogyridaen monogeneans specific to African freshwater Cichlidae and other representatives of Dactylogyridae, including a wide range of species from both freshwater and marine environments. All phylogenetic analyses point to the polyphyletic origin of the subfamily Ancyrocephalinae. Both Enterogyrus and Onchobdella were found to be monophyletic. The phylogenetic position of Scutogyrus longicornis was placed within the Cichlidogyrus species, which suggests the non-monophyly of Cichlidogyrus. Therefore, we have proposed a taxonomical revision of the species recently considered to be Scutogyrus. However, these four dactylogyridean genera-specific to cichlids do not form a monophyletic group. Using LSU rDNA analyses, we found that Enterogyrus and Onchobdella form a clade with Protogyrodactylus, i.e., the parasite species does not live in cichlids, which suggests that endoparasitism in cichlid monogeneans is not an ancestral feature.
Las Peñas, M L; Urdampilleta, J D; Bernardello, G; Forni-Martins, E R
Karyotype analyses in members of the four Cactaceae subfamilies were performed. Numbers and karyotype formula obtained were: Pereskioideae = Pereskiaaculeata(2n = 22; 10 m + 1 sm), Maihuenioideae = Maihuenia patagonica (2n = 22, 9 m + 2 sm; 2n = 44, 18 m + 4 sm), Opuntioideae = Cumulopuntia recurvata(2n = 44; 20 m + 2 sm), Cactoideae = Acanthocalycium spiniflorum (2n = 22; 10 m + 1 sm),Echinopsis tubiflora (2n = 22; 10 m + 1 sm), Trichocereus candicans (2n = 22, 22 m). Chromosomes were small, the average chromosome length was 2.3 mum. Diploid species and the tetraploid C. recurvata had one terminal satellite, whereas the remaining tetraploid species showed four satellited chromosomes. Karyotypes were symmetrical. No CMA(-)/DAPI(+) bands were detected, but CMA(+)/DAPI(-) bands associated with NOR were always found. Pericentromeric heterochromatin was found in C. recurvata, A. spiniflorum, and the tetraploid cytotype of M. patagonica. The locations of the 18S-26S rDNA sites in all species coincided with CMA(+)/DAPI(-) bands; the same occurred with the sizes and numbers of signals for each species. This technique was applied for the first time in metaphase chromosomes in cacti. NOR-bearing pair no.1 may be homeologous in all species examined. In Cactaceae, the 18S-26S loci seem to be highly conserved.
Shi, T.; Reeves, R. H.; Gilichinsky, D. A.; Friedmann, E. I.
Viable bacteria were found in permafrost core samples from the Kolyma-Indigirka lowland of northeast Siberia. The samples were obtained at different depths; the deepest was about 3 million years old. The average temperature of the permafrost is -10 degrees C. Twenty-nine bacterial isolates were characterized by 16S rDNA sequencing and phylogenetic analysis, cell morphology, Gram staining, endospore formation, and growth at 30 degrees C. The majority of the bacterial isolates were rod shaped and grew well at 30 degrees C; but two of them did not grow at or above 28 degrees C, and had optimum growth temperatures around 20 degrees C. Thirty percent of the isolates could form endospores. Phylogenetic analysis revealed that the isolates fell into four categories: high-GC Gram-positive bacteria, beta-proteobacteria, gamma-proteobacteria, and low-GC Gram-positive bacteria. Most high-GC Gram-positive bacteria and beta-proteobacteria, and all gamma-proteobacteria, came from samples with an estimated age of 1.8-3.0 million years (Olyor suite). Most low-GC Gram-positive bacteria came from samples with an estimated age of 5,000-8,000 years (Alas suite).
Terracol, R; Prud'homme, N
In Drosophila melanogaster, the multiply repeated genes encoding 18S and 28S rRNA are located on the X and Y chromosomes. A large percentage of these repeats are interrupted in the 28S region by insertions of two types. We compared the restriction patterns from a subcloned wild-type Oregon R strain to those of spontaneous and ethyl methanesulfonate-induced bobbed mutants. Bobbed mutations were found to be deficiencies that modified the organization of the rDNA locus. Genes without insertions were deleted about twice as often as genes with type I insertions. Type II insertion genes were not decreased in number, except in the mutant having the most bobbed phenotype. Reversion to wild type was associated with an increase in gene copy number, affecting exclusively genes without insertions. One hypothesis which explains these results is the partial clustering of genes by type. The initial deletion could then be due either to an unequal crossover or to loss of material without exchange. Some of our findings indicated that deletion may be associated with an amplification phenomenon, the magnitude of which would be dependent on the amount of clustering of specific gene types at the locus. Images PMID:3023865
Yadav, Shailendra; Kundu, Sharbadeb; Ghosh, Sankar K.; Maitra, S. S.
Methanogens, a key contributor in global carbon cycling, methane emission, and alternative energy production, generate methane gas via anaerobic digestion of organic matter. The methane emission potential depends upon methanogenic diversity and activity. Since they are anaerobes and difficult to isolate and culture, their diversity present in the landfill sites of Delhi and marshlands of Southern Assam, India, was analyzed using molecular techniques like 16S rDNA sequencing, DGGE, and qPCR. The sequencing results indicated the presence of methanogens belonging to the seventh order and also the order Methanomicrobiales in the Ghazipur and Bhalsawa landfill sites of Delhi. Sequences, related to the phyla Crenarchaeota (thermophilic) and Thaumarchaeota (mesophilic), were detected from marshland sites of Southern Assam, India. Jaccard analysis of DGGE gel using Gel2K showed three main clusters depending on the number and similarity of band patterns. The copy number analysis of hydrogenotrophic methanogens using qPCR indicates higher abundance in landfill sites of Delhi as compared to the marshlands of Southern Assam. The knowledge about “methanogenic archaea composition” and “abundance” in the contrasting ecosystems like “landfill” and “marshland” may reorient our understanding of the Archaea inhabitants. This study could shed light on the relationship between methane-dynamics and the global warming process. PMID:26568700
Dammann, R; Lucchini, R; Koller, T; Sogo, J M
The chromatin structure of yeast ribosomal DNA was analyzed in vivo by crosslinking intact cells with psoralen. We found that in exponentially growing cultures the regions coding for the 35S rRNA precursor fall into two distinct classes. One class was highly accessible to psoralen and associated with nascent RNAs, characteristic for transcriptionally active rRNA genes devoid of nucleosomes, whereas the other class showed a crosslinking pattern indistinguishable from that of bulk chromatin and was interpreted to represent the inactive rRNA gene copies. By crosslinking the same strain growing in complex or minimal medium, we have shown that yeast cells can modulate the proportion of active (non-nucleosomal) and inactive (nucleosomal) rRNA gene copies in response to variations in environmental conditions which suggests that yeast can regulate rRNA synthesis by varying the number of active gene copies, in contrast to the vertebrate cells studied so far. Whereas intergenic spacers flanking inactive rRNA gene copies are packaged in a regular nucleosomal array, spacers flanking active genes show an unusual crosslinking pattern suggesting a complex interaction of regulatory factors and histones with DNA. Images PMID:8506130
Chalup, Laura; Samoluk, Sergio Sebastián; Neffa, Viviana Solís; Seijo, Guillermo
Notolathyrus is a section of South American endemic species of the genus Lathyrus. The origin, phylogenetic relationship and delimitation of some species are still controversial. The present study provides an exhaustive analysis of the karyotypes of approximately half (10) of the species recognized for section Notolathyrus and four outgroups (sections Lathyrus and Orobus) by cytogenetic mapping of heterochromatic bands and 45S and 5S rDNA loci. The bulk of the parameters analyzed here generated markers to identify most of the chromosomes in the complements of the analyzed species. Chromosome banding showed interspecific variation in the amount and distribution of heterochromatin, and together with the distribution of rDNA loci, allowed the characterization of all the species studied here. Additionally, some of the chromosome parameters described (st chromosomes and the 45S rDNA loci) constitute the first diagnostic characters for the Notolathyrus section. Evolutionary, chromosome data revealed that the South American species are a homogeneous group supporting the monophyly of the section. Variation in the amount of heterochromatin was not directly related to the variation in DNA content of the Notolathyrus species. However, the correlation observed between the amount of heterochromatin and some geographical and bioclimatic variables suggest that the variation in the heterochromatic fraction should have an adaptive value.
Sousa, A; Barros e Silva, A E; Cuadrado, A; Loarce, Y; Alves, M V; Guerra, M
Secondary constrictions or 45S rDNA sites are commonly reported to be located mainly in the terminal regions of the chromosomes. This distribution has been assumed to be related to the existence of a "chromosome field" lying between the centromere and the telomere, an area in which certain cytogenetic events may predominantly occur. If this hypothesis is true this distribution should not be observed in holokinetic chromosomes, as they do not have a localized centromere. In order to evaluate this hypothesis, a comparative study was made of the distributions of 5S and 45S rDNA sites using fluorescence in situ hybridization in representatives of the genera Eleocharis, Diplacrum, Fimbristylis, Kyllinga and Rhynchospora, all of which belong to the family Cyperaceae. The numbers of sites per diploid chromosome complement varied from 2 to ∼10 for 5S rDNA, and from 2 to ∼45 for 45S rDNA. All of the 11 species analyzed had terminally located 45S rDNA sites on the chromosomes whereas the 5S rDNA sites also generally had terminal distributions, except for the Rhynchospora species, where their position was almost always interstitial. These results, together with other previously published data, suggest that the variation in the number and position of the rDNA sites in species with holokinetic chromosomes is non-random and similar to that reported for species with monocentric chromosomes. Therefore, the predominant terminal position of the 45S rDNA sites does not appear to be influenced by the centromere-telomere polarization as suggested by the "chromosome field" hypothesis. Additionally, the hybridization of 5S and 45S rDNA sites provides interesting markers to distinguish several chromosomes on the rather symmetrical karyotypes of Cyperaceae.
Njiru, Z K; Constantine, C C; Guya, S; Crowther, J; Kiragu, J M; Thompson, R C A; Dávila, A M R
There are 11 different pathogenic trypanosomes in trypanosomiasis endemic regions of Africa. Their detection and characterisation by molecular methods relies on species-specific primers; consequently several PCR tests have to be made on each sample. Primers ITS1 CF and ITS1 BR, previously designed to amplify the internal transcribed spacer (ITS1) of rDNA, have been evaluated for use in a universal diagnostic test for all pathogenic trypanosomes. Blood was collected from 373 cattle and 185 camels. The primers gave constant PCR products with the stocks of each taxon tested. Members of subgenus Trypanozoon (T. brucei brucei, T. evansi, T. b. rhodesiense and T. b. gambiense) gave a constant product of approximately 480 bp; T. congolense, savannah 700 bp, T. congolense kilifi 620 bp and T. congolense forest 710 bp: T. simiae 400 bp, T. simiae tsavo 370 bp, T. godfreyi 300 bp and T. vivax 250 bp. The sensitivity of the test ranged from 10 pg for Trypanozoon, T. congolense clade and T. vivax to 100 pg for T. simiae and T. godfreyi. The primers detected cases of multi-taxa samples, although the sensitivity was reduced with an increase in the combinations. A better detection rate of trypanosome DNA was recorded with buffy coats than from direct blood. With the field samples, the diagnostic sensitivity was close to the sensitivity obtained using single reactions with species-specific primers for Trypanozoon 38/40 (95%) and T. congolense savannah 30/33 (90.9%) but was lower with T. vivax 25/31 (77.4%). The primers offer promise as a routine diagnostic tool through the use of a single PCR; however, further evaluation is recommended.
Taylan, Mehmet Sait; Russo, Claudio Di; Rampini, Mauro; Ketmaier, Valerio
Abstract This study focuses on the evolutionary relationships among Turkish species of the cave cricket genus Troglophilus.Fifteen populations were studied for sequence variation in a fragment (543 base pairs) of the mitochondrial DNA (mtDNA) 16S rDNA gene (16S) to reconstruct their phylogenetic relationships and biogeographic history. Genetic data retrieved three main clades and at least three divergent lineages that could not be attributed to any of the taxa known for the area. Molecular time estimates suggest that the diversification of the group took place between the Messinian and the Plio-Pleistocene. PMID:23653493
Golub, Natalia V.; Golub, Viktor B.; Kuznetsova, Valentina G.
Abstract Male karyotypes of Elasmotropis testacea (Herrich-Schaeffer, 1835), Tingis cardui (Linnaeus, 1758), Tingis crispata (Herrich-Schaeffer, 1838), and Agramma femorale Thomson, 1871 (Heteroptera, Cimicomorpha, Tingidae) were analyzed using conventional chromosome staining and FISH with 18S rDNA and (TTAGG)n telomeric probes. The FISH technique was applied for the first time in the Tingidae. In spite of the fact that all species showed the same chromosome number (2n = 12 + XY), they have significant differences in the number and position of rDNA loci. FISH with the classical insect (TTAGG)n probe produced no signals on chromosomes suggesting telomeres in lace bugs to be of some other molecular composition. Tingidae share absence of the (TTAGG)n telomeric sequence with all so far studied taxa of the advanced true bug infraorders Cimicomorpha and Pentatomomorpha. PMID:26753071
Lan, T; Zhang, S; Liu, B; Li, X; Chen, R; Song, W
Spinacia oleracea L. (spinach) is a dioecious species with both male and female plants having 2n = 2x = 12 chromosomes, consisting of two large metacentrics, two long subtelocentrics, two short subtelocentrics, two acrocentrics, and four submetacentrics. The location of 45S rDNA was investigated on metaphase chromosomes using fluorescence in situ hybridization (FISH). The numbers of 45S rDNA foci in diploid sets of chromosomes from females was six and from males was five. All the fluorescent foci lay in secondary constrictions and the satellites. Our results indicate that an XY-type sex chromosome system could be present in spinach where the Y chromosome lacks a 45S RNA focus.
Resende, Deisy V; Pedrosa, André L; Correia, Dalmo; Cabrine-Santos, Marlene; Lages-Silva, Eliane; Meira, Wendell S F; Oliveira-Silva, Márcia B
Intraspecific variability among Cystoisospora belli isolates and its clinical implications in human cystoisosporosis have not been established. In this study, the restriction fragment length polymorphisms in a 1.8-kb amplicon of the small subunit ribosomal DNA (SSU rDNA) of the parasite was investigated in 20 C. belli-positive stool samples obtained from 15 HIV-infected patients. Diarrheic syndrome was observed in all patients with cystoisosporosis and the number of diarrheic episodes per patient during hospitalization ranged from 1 to 26 (mean of 9.64 ± 9.30), with a mean duration of 2 to 12 days (mean of 5.90 ± 3 days). Three restriction profiles (RF) were generated with MboII digestion, which were named RFI, RFII, and RFIII. Two isolates obtained from a patient with extraintestinal cystoisosporosis showed distinct restriction profiles with MboII. This study demonstrates that patients can be infected with different C. belli genotypes, and this information may be useful for identifying new C. belli genotypes infecting humans.
Pathipati, Padmaja; Menon, Thangam; Kumar, Naveen; Francis, Thara; Sekar, Prem; Cherian, Kotturathu Mammen
We report a rare case of infective endocarditis caused by Corynebacterium diphtheriae in an 8-year-old boy, 2 years after a right ventricular outflow tract reconstruction with a bovine Contegra valved conduit. The patient recovered well after an RV-PA conduit enblock explantation and replacement with an aortic homograft with antibiotic treatment. All bacteriological cultures of excised tissue and blood were negative. The aetiological agent was identified as C. diphtheriae subsp. gravis by 16s rDNA sequencing.
Li, Yanyan; Shen, Songdong; He, Lihong; Xu, Pu; Wang, Guangce
The sequences of the ITS (internal transcribed spacer) and 5.8S rDNA of three cultivated strains of Porphyra haitanensis thalli (NB, PT and ST) were amplified, sequenced and analyzed. In addition, the phylogenic relationships of the sequences identified in this study with those of other Porphyra retrieved from GenBank were evaluated. The results are as follows: the sequences of the ITS and 5.8S rDNA were essentially identical among the three strains. The sequences of ITS1 were 331 bp to 334 bp, while those of the 5.8S rDNA were 158 bp and the sequences of ITS2 ranged from 673 bp to 681 bp. The sequences of the ITS had a high level of homology (up to 99.5%) with that of P. haitanensis (DQ662228) retrieved from GenBank, but were only approximately 50% homologous with those of other species of Porphyra. The results obtained when a phylogenetic tree was constructed coincided with the results of the homology analysis. These results suggest that the three cultivated strains of P. haitanensis evolved conservatively and that the ITS showed evolutionary consistency. However, the sequences of the ITS and 5.8S rDNA of different Porphyra species showed great variations. Therefore, the relationship of Porphyra interspecies phyletic evolution could be judged, which provides the proof for Porphyra identification study. However, proper classifications of the subspecies and the populations of Porphyra should be determined through the use of other molecular techniques to determine the genetic variability and rational phylogenetic relationships.
Fernandez-Tajes, Juan; Méndez, Josefina
Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis of the 5S ribosomal DNA region has been applied to the establishment of DNA-based molecular markers for the identification of five razor clam species: Ensis arcuatus, E. siliqua, E. directus, E. macha, and Solen marginatus. PCR amplifications were carried out using a pair of universal primers from the coding region of 5S rDNA. S. marginatus was simply distinguished by the different size of the amplicons obtained. Species-specific restriction endonuclease patterns were found with the enzymes Hae III for E. arcuatus, E. siliqua, and E. directus, and Acs I for E. macha, and when two enzymes were combined, the four species were also identified. Thus, this work provides a simple, reliable, and rapid protocol for the accurate identification of Ensis and Solen species in fresh and canned products, which is very useful for traceability and to enforce labeling regulations.
Pizzaia, D; Oliveira, V M; Martins, A R; Appezzato-da-Glória, B; Forni-Martins, E; Aguiar-Perecin, M L R
The genus Smilax (Smilacaceae) includes species of medicinal interest; consequently, their identification is important for the control of raw material used in the manufacture of phytotherapeutic products. We investigated the karyotype of Smilax rufescens in order to look for patterns that would be useful for comparative studies of this genus. To accomplish this, we developed procedures to grow plants and optimize root pretreatment with mitotic fuse inhibitors to obtain metaphase spreads showing clear chromosome morphology. The karyotype, analyzed in Feulgen-stained preparations, was asymmetric, with N = 16 chromosomes gradually decreasing in size; the larger ones were subtelocentric and the smaller chromosomes were submetacentric or metacentric. Nearly terminal secondary constrictions were visualized on the short arm of chromosome pairs 7, 11, and 14, but they were clearly detected only in one of the homologues of each pair. The nucleolus organizer regions (NORs) were mapped by silver staining and fluorescent in situ hybridization of 45S rDNA probes. Silver signals (Ag-NORs) colocalized with rDNA loci were detected at the termini of the short arm of 6 chromosomes. The secondary constriction heteromorphism observed in Feulgen-stained metaphases suggests that differential rRNA gene expression between homologous rDNA loci can occur, resulting in different degrees of chromatin decondensation. In addition, a heteromorphic chromosome pair was identified and was interpreted as being a sex chromosome pair in this dioecious species.
Van Wormhoudt, Alain; Gaume, Béatrice; Le Bras, Yvan; Roussel, Valérie; Huchette, Sylvain
Analysis of the 18S rDNA sequences of Haliotis tuberculata tuberculata and H. t. coccinea subtaxa identified two different types of 18S rDNA genes and ITS1 regions. These two different genes were also detected in H. marmorata, H. rugosa and H. diversicolor that are separated from H. tuberculata by 5-65 mya. The mean divergence value between type I and type II sequences ranged from 7.25% for 18S to 80% for ITS1. ITS1 type II is homologous with the ITS1 consensus sequences published for many abalone species, whereas ITS1 type I presented only minor homology with a unique database entry for H. iris ITS1. A phylogenetic analysis makes a clear separation between type I and type II ITS1 sequences and supports grouping H. t. tuberculata, H. t. coccinea and H. marmorata together. The two subtaxa do not show any significant differences between the homologous 18S rDNA sequences. A general structure of the ITS1 transcript was proposed, with four major helices for the two types. The two genes were expressed and, for the first time, a putative differential expression of ITS1 type I was detected in the gills, digestive gland and gonads whereas ITS1 type II was expressed in all tissues.
Kim, Wonyong; Song, Mi-Ok; Song, Wonkeun; Kim, Ki-Jung; Chung, Sang-In; Choi, Chul-Soon; Park, Yong-Ha
16S rDNA sequence analysis and repetitive element sequence-based PCR (rep-PCR) genomic fingerprinting were evaluated on 11 type strains of the genus Yersinia and 17 recognized serotype strains of Y. pseudotuberculosis to investigate their genetic relatedness and to establish the value of techniques for the identification of Y. pseudotuberculosis. A phylogenetic tree constructed from 16S rDNA sequences showed that the type strains of Yersinia species formed distinct clusters with the exception of Y. pestis and Y. pseudotuberculosis. Moreover, Y. pestis NCTC 5923T was found to be closely related to Y. pseudotuberculosis serotypes 1b, 3, and 7. Dendrograms generated from REP-PCR, and ERIC-PCR data revealed that members of the genus Yersinia differed from each other with the degree of similarity 62% and 58%, respectively. However, the BOX-PCR results showed that Y. pestis 5923T clustered with the Y. pseudotuberculosis group with a degree of similarity 74%. According to these findings, 16S rDNA sequence analysis was unable to reliably discriminate Y. pseudotuberculosis from Y. pestis. However, REP-PCR and especially ERIC-PCR provided an effective means of differentiating between members of the taxa.
Walochnik, J; Obwaller, A; Aspöck, H
Various species of the genus Acanthamoeba have been described as potential pathogens; however, differentiation of acanthamoebae remains problematic. The genus has been divided into 12 18S rDNA sequence types, most keratitis causing strains exhibiting sequence type T4. We recently isolated a keratitis causing Acanthamoeba strain showing sequence type T6, but being morphologically identical to a T4 strain. The aim of our study was to find out, whether the 18S rDNA sequence based identification correlates to immunological differentiation. The protein and antigen profiles of the T6 isolate and three reference Acanthamoeba strains were investigated using two sera from Acanthamoeba keratitis patients and one serum from an asymptomatic individual. It was shown, that the T6 strain produces a distinctly different immunological pattern, while patterns within T4 were identical. Affinity purified antibodies were used to further explore immunological cross-reactivity between sequence types. Altogether, the results of our study support the Acanthamoeba 18S rDNA sequence type classification in the investigated strains.
Schwenk, Dagmar; Nohynek, Liisa; Rischer, Heiko
Forty cultivable, visually distinct bacterial cultures were isolated from four Baltic microalgal cultures Chlorella pyrenoidosa, Scenedesmus obliquus, Isochrysis sp., and Nitzschia microcephala, which have been maintained for several years in the laboratory. Bacterial isolates were characterized with respect to morphology, antibiotic susceptibility, and 16S ribosomal DNA sequence. A total of 17 unique bacterial strains, almost all belonging to one of three families, Rhodobacteraceae, Rhizobiaceae, and Erythrobacteraceae, were subsequently isolated. The majority of isolated bacteria belong to Rhodobacteraceae. Literature review revealed that close relatives of the bacteria isolated in this study are not only often found in marine environments associated with algae, but also in lakes, sediments, and soil. Some of them had been shown to interact with organisms in their surroundings. A Basic Local Alignment Search Tool study indicated that especially bacteria isolated from the Isochrysis sp. culture were highly similar to microalgae-associated bacteria. Two of those isolates, I1 and I6, belong to the Cytophaga-Flavobacterium-Bacteroides phylum, members of which are known to occur in close communities with microalgae. An UniFrac analysis revealed that the bacterial community of Isochrysis sp. significantly differs from the other three communities.
Li, G Q; Hu, Y L; Kanu, S; Zhu, X Q
The first internal transcribed spacer (ITS1) of nuclear ribosomal DNA from Culicoides arakawae was amplified by PCR, cloned and sequenced. The wDNAsis software was used to analyze the ITS1 sequences of C. arakawae and other nine species of Culicoides, which were obtained from GenBank and EMBL databases. For all species, the lengths of the ITS1 were 316-469 bp, and the G+C contents were 26.79-34.53%. Based on the lengths of the ITS1 sequences, the 10 Culicoides species could be divided into two groups. The first group consisted of C. arakawae, C. albicans, C. cubitalis, C. pulicaris and C. punctatus, and the second group comprised C. impunctatus, C. nubeculosus, C. variipennis, C. grisescens and C. imicola. The lengths for the first group were 316-347 bp and the second group were 457-469 bp. C. arakawae belonged to the first group by its ITS1 sequence length. Sequence analysis revealed that C. arakawae was genetically more similar to the first group than it was to the second group, consistent with results based on sequence length. The alignment of ITS1 (the alignment length was 500 bp including the gaps) sequences showed that there was a highly conserved region, which was between 288 and 388 bp, except for a few insertions and substitutions. These findings have important implications for the molecular identification of C. arakawae, for studying its molecular genetics and epidemiology, and for studying the molecular systematics of Culicoides.
Background Bacterial taxonomy and phylogeny based on rrs (16S rDNA) sequencing is being vigorously pursued. In fact, it has been stated that novel biological findings are driven by comparison and integration of massive data sets. In spite of a large reservoir of rrs sequencing data of 1,237,963 entries, this analysis invariably needs supplementation with other genes. The need is to divide the genetic variability within a taxa or genus at their rrs phylogenetic boundaries and to discover those fundamental features, which will enable the bacteria to naturally fall within them. Within the large bacterial community, Clostridium represents a large genus of around 110 species of significant biotechnological and medical importance. Certain Clostridium strains produce some of the deadliest toxins, which cause heavy economic losses. We have targeted this genus because of its high genetic diversity, which does not allow accurate typing with the available molecular methods. Results Seven hundred sixty five rrs sequences (> 1200 nucleotides, nts) belonging to 110 Clostridium species were analyzed. On the basis of 404 rrs sequences belonging to 15 Clostridium species, we have developed species specific: (i) phylogenetic framework, (ii) signatures (30 nts) and (iii) in silico restriction enzyme (14 Type II REs) digestion patterns. These tools allowed: (i) species level identification of 95 Clostridium sp. which are presently classified up to genus level, (ii) identification of 84 novel Clostridium spp. and (iii) potential reduction in the number of Clostridium species represented by small populations. Conclusions This integrated approach is quite sensitive and can be easily extended as a molecular tool for diagnostic and taxonomic identification of any microbe of importance to food industries and health services. Since rapid and correct identification allows quicker diagnosis and consequently treatment as well, it is likely to lead to reduction in economic losses and mortality
Hoy, Marshal S.; Rodriguez, Rusty J.
Molecular genetic analysis was conducted on two populations of the invasive non-native New Zealand mud snail (Potamopyrgus antipodarum), one from a freshwater ecosystem in Devil's Lake (Oregon, USA) and the other from an ecosystem of higher salinity in the Columbia River estuary (Hammond Harbor, Oregon, USA). To elucidate potential genetic differences between the two populations, three segments of nuclear ribosomal DNA (rDNA), the ITS1-ITS2 regions and the 18S and 28S rDNA genes were cloned and sequenced. Variant sequences within each individual were found in all three rDNA segments. Folding models were utilized for secondary structure analysis and results indicated that there were many sequences which contained structure-altering polymorphisms, which suggests they could be nonfunctional pseudogenes. In addition, analysis of molecular variance (AMOVA) was used for hierarchical analysis of genetic variance to estimate variation within and among populations and within individuals. AMOVA revealed significant variation in the ITS region between the populations and among clones within individuals, while in the 5.8S rDNA significant variation was revealed among individuals within the two populations. High levels of intragenomic variation were found in the ITS regions, which are known to be highly variable in many organisms. More interestingly, intragenomic variation was also found in the 18S and 28S rDNA, which has rarely been observed in animals and is so far unreported in Mollusca. We postulate that in these P. antipodarum populations the effects of concerted evolution are diminished due to the fact that not all of the rDNA genes in their polyploid genome should be essential for sustaining cellular function. This could lead to a lessening of selection pressures, allowing mutations to accumulate in some copies, changing them into variant sequences.
Moreira, David; von der Heyden, Sophie; Bass, David; López-García, Purificación; Chao, Ema; Cavalier-Smith, Thomas
Resolution of the phylogenetic relationships among the major eukaryotic groups is one of the most important problems in evolutionary biology that is still only partially solved. This task was initially addressed using a single marker, the small-subunit ribosomal DNA (SSU rDNA), although in recent years it has been shown that it does not contain enough phylogenetic information to robustly resolve global eukaryotic phylogeny. This has prompted the use of multi-gene analyses, especially in the form of long concatenations of numerous conserved protein sequences. However, this approach is severely limited by the small number of taxa for which such a large number of protein sequences is available today. We have explored the alternative approach of using only two markers but a large taxonomic sampling, by analysing a combination of SSU and large-subunit (LSU) rDNA sequences. This strategy allows also the incorporation of sequences from non-cultivated protists, e.g., Radiozoa (=radiolaria minus Phaeodarea). We provide the first LSU rRNA sequences for Heliozoa, Apusozoa (both Apusomonadida and Ancyromonadida), Cercozoa and Radiozoa. Our Bayesian and maximum likelihood analyses for 91 eukaryotic combined SSU+LSU sequences yielded much stronger support than hitherto for the supergroup Rhizaria (Cercozoa plus Radiozoa plus Foraminifera) and several well-recognised groups and also for other problematic clades, such as the Retaria (Radiozoa plus Foraminifera) and, with more moderate support, the Excavata. Within opisthokonts, the combined tree strongly confirms that the filose amoebae Nuclearia are sisters to Fungi whereas other Choanozoa are sisters to animals. The position of some bikont taxa, notably Heliozoa and Apusozoa, remains unresolved. However, our combined trees suggest a more deeply diverging position for Ancyromonas, and perhaps also Apusomonas, than for other bikonts, suggesting that apusozoan zooflagellates may be central for understanding the early evolution of
He, Weiguo; Qin, Qinbo; Liu, Shaojun; Li, Tangluo; Wang, Jing; Xiao, Jun; Xie, Lihua; Zhang, Chun; Liu, Yun
Through distant crossing, diploid, triploid and tetraploid hybrids of red crucian carp (Carassius auratus red var., RCC♀, Cyprininae, 2n = 100) × topmouth culter (Erythroculter ilishaeformis Bleeker, TC♂, Cultrinae, 2n = 48) were successfully produced. Diploid hybrids possessed 74 chromosomes with one set from RCC and one set from TC; triploid hybrids harbored 124 chromosomes with two sets from RCC and one set from TC; tetraploid hybrids had 148 chromosomes with two sets from RCC and two sets from TC. The 5S rDNA of the three different ploidy-level hybrids and their parents were sequenced and analyzed. There were three monomeric 5S rDNA classes (designated class I: 203 bp; class II: 340 bp; and class III: 477 bp) in RCC and two monomeric 5S rDNA classes (designated class IV: 188 bp, and class V: 286 bp) in TC. In the hybrid offspring, diploid hybrids inherited three 5S rDNA classes from their female parent (RCC) and only class IV from their male parent (TC). Triploid hybrids inherited class II and class III from their female parent (RCC) and class IV from their male parent (TC). Tetraploid hybrids gained class II and class III from their female parent (RCC), and generated a new 5S rDNA sequence (designated class I-N). The specific paternal 5S rDNA sequence of class V was not found in the hybrid offspring. Sequence analysis of 5S rDNA revealed the influence of hybridization and polyploidization on the organization and variation of 5S rDNA in fish. This is the first report on the coexistence in vertebrates of viable diploid, triploid and tetraploid hybrids produced by crossing parents with different chromosome numbers, and these new hybrids are novel specimens for studying the genomic variation in the first generation of interspecific hybrids, which has significance for evolution and fish genetics.
Ivanova, N V; Morozov, E H; Kukina, I V; Maksakovskaia, E V; Rabinovich, S A; Poltaraus, A B
Stages life cycle of the malaria parasite differ in the rate of replication and the structural properties of functionally active A-, S-, and O-type ribosomes. Regions of A-type rDNA including ITS1, 5.8S, and ITS2 from two strains of Plasmodium vivax with different incubation periods were amplified and sequenced. No substantial differences in the sequences of two strains were revealed. Phylogenetic analysis of the obtained and homologous sequences of ITS1 rDNA of A, S, and O types of P. vivax; A and S types of P. falciparum; and Cryptosporidium parvum, Eimeria maxima, Toxoplasma gondii as outgroup, by the maximum parsimony method using PAUP 4.0 revealed that divergence of ITS1 might have occurred after speciation and at different rates in individual lineages of the Plasmodium genus. Basing on the results of the analysis of orthologous sequences of P. vivax and P. falciparum, we developed genus- and species-specific primers for PCR diagnostics of malaria, as well as a one-step effective method of DNA isolation from Giemsa-Romanovsky-stained thick blood smears. It was demonstrated that stained preparations could be a reliable source of plasmodial DNA, and the quality of preparations and storage time (10-20 years) did not interfere with the results of PCR analysis.
Ye, Weimin; Szalanski, Allen L.; Robbins, R. T.
Genetic analyses using DNA sequences of nuclear ribosomal DNA ITS1 were conducted to determine the extent of genetic variation within and among Longidorus and Xiphinema species. DNA sequences were obtained from samples collected from Arkansas, California and Australia as well as 4 Xiphinema DNA sequences from GenBank. The sequences of the ITS1 region including the 3' end of the 18S rDNA gene and the 5' end of the 5.8S rDNA gene ranged from 1020 bp to 1244 bp for the 9 Longidorus species, and from 870 bp to 1354 bp for the 7 Xiphinema species. Nucleotide frequencies were: A = 25.5%, C = 21.0%, G = 26.4%, and T = 27.1%. Genetic variation between the two genera had a maximum divergence of 38.6% between X. chambersi and L. crassus. Genetic variation among Xiphinema species ranged from 3.8% between X. diversicaudatum and X. bakeri to 29.9% between X. chambersi and X. italiae. Within Longidorus, genetic variation ranged from 8.9% between L. crassus and L. grandis to 32.4% between L. fragilis and L. diadecturus. Intraspecific genetic variation in X. americanum sensu lato ranged from 0.3% to 1.9%, while genetic variation in L. diadecturus had 0.8% and L. biformis ranged from 0.6% to 10.9%. Identical sequences were obtained between the two populations of L. grandis, and between the two populations of X. bakeri. Phylogenetic analyses based on the ITS1 DNA sequence data were conducted on each genus separately using both maximum parsimony and maximum likelihood analysis. Among the Longidorus taxa, 4 subgroups are supported: L. grandis, L. crassus, and L. elongatus are in one cluster; L. biformis and L. paralongicaudatus are in a second cluster; L. fragilis and L. breviannulatus are in a third cluster; and L. diadecturus is in a fourth cluster. Among the Xiphinema taxa, 3 subgroups are supported: X. americanum with X. chambersi, X. bakeri with X. diversicaudatum, and X. italiae and X. vuittenezi forming a sister group with X. index. The relationships observed in this study
Lu, Borong; Wang, Chundi; Huang, Jie; Shi, Yuhong; Chen, Xiangrui
The morphology and phylogeny of two hypotrichous ciliates, Metaurostylopsis parastruederkypkeae n. sp. and Neourostylopsis flavicana (Wang et al., 2011) Chen et al., 2013 were investigated based on morphology, infraciliature and the small subunit (SSU) ribosomal RNA gene (rRNA) sequence. The new species, M. parastruederkypkeae n. sp. was identified according to its characteristics: body shape ellipsoidal, size about (165-200) × (45-60) μm in vivo, cell color reddish; two types of cortical granules including wheat grain-like and yellow-greenish larger ones along the marginal cirri rows and dorsal kineties and dot-like and reddish smaller ones, grouped around marginal cirri on ventral side and arranged in short lines on dorsal side; 26-41 adoral membranelles; three frontal and one parabuccal, five to seven frontoterminal, one buccal, and three to six transverse cirri; seven to thirteen midventral pairs; five to nine unpaired ventral cirri, five to seven left and three to five right marginal rows; and three complete dorsal kineties. Phylogenetic analysis based on SSU rDNA sequences showed that both Metaurostylopsis and Neourostylopsis are monophyletic. As the internal relationship between and within both genera are not clear, further studies on the species in these two genera are necessary. The key characteristics of all known twelve Metaurostylopsis-Apourostylopsis-Neourostylopsis species complex were updated.
Coolen, Marco J L; Talbot, Helen M; Abbas, Ben A; Ward, Christopher; Schouten, Stefan; Volkman, John K; Damsté, Jaap S Sinninghe
Bacteriohopanoids are widespread lipid biomarkers in the sedimentary record. Many aerobic and anaerobic bacteria are potential sources of these lipids which sometimes complicates the use of these biomarkers as proxies for ecological and environmental changes. Therefore, we applied preserved 16S ribosomal RNA genes to identify likely Holocene biological sources of bacteriohopanepolyols (BHPs) in the sulfidic sediments of the permanently stratified postglacial Ace Lake, Antarctica. A suite of intact BHPs were identified, which revealed a variety of structural forms whose composition differed through the sediment core reflecting changes in bacterial populations induced by large changes in lake salinity. Stable isotopic compositions of the hopanols formed from periodic acid-cleaved BHPs, showed that some were substantially depleted in (13)C, indicative of their methanotrophic origin. Using sensitive molecular tools, we found that Type I and II methanotrophic bacteria (respectively Methylomonas and Methylocystis) were unique to the oldest lacustrine sediments (> 9400 years BP), but quantification of fossil DNA revealed that the Type I methanotrophs, including methanotrophs related to methanotrophic gill symbionts of deep-sea cold-seep mussels, were the main precursors of the 35-amino BHPs (i.e. aminopentol, -tetrol and -triols). After isolation of the lake approximately 3000 years ago, one Type I methanotroph of the 'methanotrophic gill symbionts cluster' remained the most obvious source of aminotetrol and -triol. We, furthermore, identified a Synechococcus phylotype related to pelagic freshwater strains in the oldest lacustrine sediments as a putative source of 2-methylbacteriohopanetetrol (2-Me BHT). This combined application of advanced geochemical and paleogenomical tools further refined our knowledge about Holocene biogeochemical processes in Ace Lake.
Macas, Jiri; Navrátilová, Alice; Mészáros, Tibor
We cloned and sequenced the Vicia sativa 25S-18S rDNA intergenic spacer (IGS) and the satellite repeat S12, thought to be related to the spacer sequence. The spacer was shown to contain three types of subrepeats (A, B, and C) with monomers of 173 bp (A), 10 bp (B), and 66 bp (C), separated by unique or partially duplicated sequences. Two spacer variants were detected in V. sativa that differed in length (2990 and 3168 bp) owing to an extra copy of the subrepeat A. The A subrepeats were also shown to be highly homologous to the satellite repeat S12, which is located in large clusters on chromosomes 4, 5, and 6, and is not associated with the rDNA loci. Sequencing of additional S12 clones retrieved from a shotgun genomic library allowed definition of three subfamilies of this repeat based on minor differences in their nucleotide sequences. Two of these subfamilies could be discriminated from the rest of the S12 sequences as well as from the IGS A subrepeats using specific oligonucleotide primers that labeled only a subset of the S12 loci when used in the primed in situ DNA labeling (PRINS) reaction on mitotic chromosomes. These experiments showed that, in spite of the high overall similarity of the IGS A subrepeats and the S12 satellite repeats, there are S12 subfamilies that are divergent from the common consensus and are present at only some of the chromosomes containing the S12 loci. Thus, the subfamilies may have evolved at these loci following the spreading of the A subrepeats from the IGS to genomic regions outside the rDNA clusters.
Zhao, Ya-E; Wu, Li-Ping
To confirm phylogenetic relationships in Demodex mites based on mitochondrial 16S rDNA partial sequences, mtDNA 16S partial sequences of ten isolates of three Demodex species from China were amplified, recombined, and sequenced and then analyzed with two Demodex folliculorum isolates from Spain. Lastly, genetic distance was computed, and phylogenetic tree was reconstructed. MEGA 4.0 analysis showed high sequence identity among 16S rDNA partial sequences of three Demodex species, which were 95.85 % in D. folliculorum, 98.53 % in Demodex canis, and 99.71 % in Demodex brevis. The divergence, genetic distance, and transition/transversions of the three Demodex species reached interspecies level, whereas there was no significant difference of the divergence (1.1 %), genetic distance (0.011), and transition/transversions (3/1) of the two geographic D. folliculorum isolates (Spain and China). Phylogenetic trees reveal that the three Demodex species formed three separate branches of one clade, where D. folliculorum and D. canis gathered first, and then gathered with D. brevis. The two Spain and five China D. folliculorum isolates did not form sister clades. In conclusion, 16S mtDNA are suitable for phylogenetic relationship analysis in low taxa (genus or species), but not for intraspecies determination of Demodex. The differentiation among the three Demodex species has reached interspecies level.
Alanio, Alexandre; Sturny-Leclère, Aude; Benabou, Marion; Guigue, Nicolas; Bretagne, Stéphane
Droplet digital PCR (ddPCR) after DNA digestion yielded a 28S rDNA copy number of 61 to 86 copies/genome when testing 10 unrelated Aspergillus fumigatus isolates, higher than with quantitative PCR. Unfortunately, ddPCR after DNA digestion did not improve the sensitivity of our PCR assay when testing serum patients with invasive aspergillosis.
Background The Internal Transcribed Spacer (ITS) regions of fungal ribosomal DNA (rDNA) are highly variable sequences of great importance in distinguishing fungal species by PCR analysis. Previously published PCR primers available for amplifying these sequences from environmenta...
Doganlar, Oguzhan; Doganlar, Zeynep Banu; Tabakcioglu, Kiymet
In this study, we aimed to investigate the mutagenic and carcinogenic potential of a volatile organic compound (VOC) mixture with references to the response of D.melanogaster using selected antioxidant gene expressions, RAPD assay and base-pair change of ribosomal 18S, and the internal transcribed spacer, ITS2 rDNA gene sequences. For this purpose, Drosophila melanogaster Oregon R, reared under controlled conditions on artificial diets, were treated with the mixture of thirteen VOCs, which are commonly found in water in concentrations of 10, 20, 50, and 75 ppb for 1 and 5 days. In the random amplified polymorphic DNA (RAPD) assay, band changes were clearly detected, especially at the 50 and 75 ppb exposure levels, for both treatment periods, and the band profiles exhibited clear differences between the treated and untreated flies with changes in band intensity and the loss/appearance of bands. Quantitative real-time PCR (qRT-PCR) analysis of Mn-superoxide dismutase (Mn-SOD), catalase (CAT) and glutathione-synthetase (GS) expressions demonstrated that these markers responded significantly to VOC-induced oxidative stress. Whilst CAT gene expressions increased linearly with increasing concentrations of VOCs and treatment times, the 50- and 75-ppb treatments caused decreases in GS expressions compared to the control at 5 days. Treatment with VOCs at both exposure times, especially in high doses, caused gene mutation of the 18S and the ITS2 ribosomal DNA. According to this research, we thought that the permissible maximum-contamination level of VOCs can cause genotoxic effect especially when mixed.
Godon, J J; Zumstein, E; Dabert, P; Habouzit, F; Moletta, R
The bacterial community structure of a fluidized-bed reactor fed by vinasses (wine distillation waste) was analyzed. After PCR amplification, four small-subunit (SSU) rDNA clone libraries of Bacteria, Archaea, Procarya, and Eucarya populations were established. The community structure was determined by operational taxonomic unit (OTU) phylogenetic analyses of 579 partial rDNA sequences (about 500 bp long). A total of 146 OTUs were found, comprising 133, 6, and 7 from the Bacteria, Archaea, and Eucarya domains, respectively. A total of 117 bacterial OTU were affiliated with major phyla: low-G+C gram-positive bacteria, Cytophaga-Flexibacter-Bacteroides, Proteobacteria, high-G+C gram-positive bacteria, and Spirochaetes, where the clone distribution was 34, 26, 17, 6, and 4%, respectively. The other 16 bacterial OTUs represent 13% of the clones. They were either affiliated with narrow phyla such as Planctomyces-Chlamydia, green nonsulfur bacteria, or Synergistes, or deeply branched on the phylogenetic tree. A large number of bacterial OTUs are not closely related to any other hitherto determined sequences. The most frequent bacterial OTUs represents less than 5% of the total bacterial SSU rDNA sequences. However, the 20 more frequent bacterial OTUs describe at least 50% of these sequences. Three of the six Archaea OTUs correspond to 95% of the Archaea population and are very similar to already known methanogenic species: Methanosarcina barkeri, Methanosarcina frisius, and Methanobacterium formicicum. In contrast, the three other Archaea OTUs are unusual and are related to thermophilic microorganisms such as Crenarchaea or Thermoplasma spp. Five percent of the sequences analyzed were chimeras and were removed from the analysis.
Godon, J J; Zumstein, E; Dabert, P; Habouzit, F; Moletta, R
The bacterial community structure of a fluidized-bed reactor fed by vinasses (wine distillation waste) was analyzed. After PCR amplification, four small-subunit (SSU) rDNA clone libraries of Bacteria, Archaea, Procarya, and Eucarya populations were established. The community structure was determined by operational taxonomic unit (OTU) phylogenetic analyses of 579 partial rDNA sequences (about 500 bp long). A total of 146 OTUs were found, comprising 133, 6, and 7 from the Bacteria, Archaea, and Eucarya domains, respectively. A total of 117 bacterial OTU were affiliated with major phyla: low-G+C gram-positive bacteria, Cytophaga-Flexibacter-Bacteroides, Proteobacteria, high-G+C gram-positive bacteria, and Spirochaetes, where the clone distribution was 34, 26, 17, 6, and 4%, respectively. The other 16 bacterial OTUs represent 13% of the clones. They were either affiliated with narrow phyla such as Planctomyces-Chlamydia, green nonsulfur bacteria, or Synergistes, or deeply branched on the phylogenetic tree. A large number of bacterial OTUs are not closely related to any other hitherto determined sequences. The most frequent bacterial OTUs represents less than 5% of the total bacterial SSU rDNA sequences. However, the 20 more frequent bacterial OTUs describe at least 50% of these sequences. Three of the six Archaea OTUs correspond to 95% of the Archaea population and are very similar to already known methanogenic species: Methanosarcina barkeri, Methanosarcina frisius, and Methanobacterium formicicum. In contrast, the three other Archaea OTUs are unusual and are related to thermophilic microorganisms such as Crenarchaea or Thermoplasma spp. Five percent of the sequences analyzed were chimeras and were removed from the analysis. PMID:9212428
Gokhman, Vladimir E; Bolsheva, Nadezhda L; Govind, Shubha; Muravenko, Olga V
Karyotypes of Leptopilina boulardi (Barbotin, Carton et Keiner-Pillault, 1979) (n = 9), L. heterotoma (Thomson, 1862) (n = 10), L. victoriae Nordlander, 1980 (n = 10) and Ganaspis xanthopoda (Ashmead, 1896) (n = 9) (Hymenoptera, Figitidae) were studied using DNA-binding ligands with different base specificity [propidium iodide (PI), chromomycin A3 (CMA3) and 4',6-diamidino-2-phenylindole (DAPI)], and fluorescence in situ hybridization (FISH) with a 45S rDNA probe. Fluorochrome staining was similar between the different fluorochromes, except for a single CMA3- and PI-positive and DAPI-negative band per haploid karyotype of each species. FISH with 45S rDNA probe detected a single rDNA site in place of the bright CMA3-positive band, thus identifying the nucleolus organizing region (NOR). Chromosomal locations of NORs were similar for both L. heterotoma and L. victoriae, but strongly differed in L. boulardi as well as in G. xanthopoda. Phylogenetic aspects of NOR localization in all studied species are briefly discussed.
De Luca, F.; Reyes, A.; Grunder, J.; Kunz, P.; Agostinelli, A.; De Giorgi, C.; Lamberti, F.
Total DNA was isolated from individual nematodes of the species Longidorus helveticus, L. macrosoma, L. arthensis, L. profundorum, L. elongatus, and L. raskii collected in Switzerland. The ITS region and D1-D2 expansion segments of the 26S rDNA were amplified and cloned. The sequences obtained were aligned in order to investigate sequence diversity and to infer the phylogenetic relationships among the six Longidorus species. D1-D2 sequences were more conserved than the ITS sequences that varied widely in primary structure and length, and no consensus was observed. Phylogenetic analyses using the neighbor-joining, maximum parsimony and maximum likelihood methods were performed with three different sequence data sets: ITS1-ITS2, 5.8S-D1-D2, and combining ITS1-ITS2+5.8S-D1-D2 sequences. All multiple alignments yielded similar basic trees supporting the existence of the six species established using morphological characters. These sequence data also provided evidence that the different regions of the rDNA are characterized by different evolution rates and by different factors associated with the generation of extreme size variation. PMID:19262800
Lee, Jiyoung; Phung, Nguyet Thu; Chang, In Seop; Kim, Byung Hong; Sung, Ha Chin
A fuel cell-type electrochemical device has been used to enrich microbes oxidizing acetate with concomitant electricity generation without using an electron mediator from activated sludge. The device generated a stable current of around 5 mA with complete oxidation of 5 mM acetate at the hydraulic retention time of 2.5 h after 4 weeks of enrichment. Over 70% of electrons available from acetate oxidation was recovered as current. Carbon monoxide or hydrogen did not influence acetate oxidation or current generation from the microbial fuel cell (MFC). Denaturing gradient gel electrophoresis showed that DNA extracted from the acetate-enriched MFC had different 16S rDNA patterns from those of sludge or glucose+glutamate-enriched MFCs. Nearly complete 16S rDNA sequence analyses showed that diverse bacteria were enriched in the MFC fed with acetate. Electron microscopic observations showed biofilm developed on the electrode, but not microbial clumps observed in MFCs fed with complex fuel such as glucose and wastewater from a corn-processing factory.
Tian, Yang; Li, Yan Hong
To understand the differences of the bacteria associated with different mosses, a phylogenetic study of bacterial communities in three mosses was carried out based on 16S rDNA and 16S rRNA sequencing. The mosses used were Hygroamblystegium noterophilum, Entodon compressus and Grimmia montana, representing hygrophyte, shady plant and xerophyte, respectively. In total, the operational taxonomic units (OTUs), richness and diversity were different regardless of the moss species and the library level. All the examined 1183 clones were assigned to 248 OTUs, 56 genera were assigned in rDNA libraries and 23 genera were determined at the rRNA level. Proteobacteria and Bacteroidetes were considered as the most dominant phyla in all the libraries, whereas abundant Actinobacteria and Acidobacteria were detected in the rDNA library of Entodon compressus and approximately 24.7% clones were assigned to Candidate division TM7 in Grimmia montana at rRNA level. The heatmap showed the bacterial profiles derived from rRNA and rDNA were partly overlapping. However, the principle component analysis of all the profiles derived from rDNA showed sharper differences between the different mosses than that of rRNA-based profiles. This suggests that the metabolically active bacterial compositions in different mosses were more phylogenetically similar and the differences of the bacteria associated with different mosses were mainly detected at the rDNA level. Obtained results clearly demonstrate that combination of 16S rDNA and 16S rRNA sequencing is preferred approach to have a good understanding on the constitution of the microbial communities in mosses.
Gan, Yimei; Liu, Fang; Chen, Dan; Wu, Qiong; Qin, Qin; Wang, Chunying; Li, Shaohui; Zhang, Xiangdi; Wang, Yuhong; Wang, Kunbo
We investigated the locations of 5S and 45S rDNA in Gossypium diploid A, B, D, E, F, G genomes and tetraploid genome (AD) using multi-probe fluorescent in situ hybridization (FISH) for evolution analysis in Gossypium genus. The rDNA numbers and sizes, and synteny relationships between 5S and 45S were revealed using 5S and 45S as double-probe for all species, and the rDNA-bearing chromosomes were identified for A, D and AD genomes with one more probe that is single-chromosome-specific BAC clone from G. hirsutum (A1D1). Two to four 45S and one 5S loci were found in diploid-species except two 5S loci in G. incanum (E4), the same as that in tetraploid species. The 45S on the 7th and 9th chromosomes and the 5S on the 9th chromosomes seemed to be conserved in A, D and AD genomes. In the species of B, E, F and G genomes, the rDNA numbers, sizes, and synteny relationships were first reported in this paper. The rDNA pattern agrees with previously reported phylogenetic history with some disagreements. Combined with the whole-genome sequencing data from G. raimondii (D5) and the conserved cotton karyotype, it is suggested that the expansion, decrease and transposition of rDNA other than chromosome rearrangements might occur during the Gossypium evolution. PMID:23826377
Swinger DNAs are sequences whose homology with known sequences is detected only by assuming systematic exchanges between nucleotides. Nine symmetric (X<->Y, i.e. A<->C) and fourteen asymmetric (X->Y->Z, i.e. A->C->G) exchanges exist. All swinger DNA previously detected in GenBank follow the A<->T+C<->G exchange, while mitochondrial swinger RNAs distribute among different swinger types. Here different alignment criteria detect 87 additional swinger mitochondrial DNAs (86 from insects), including the first swinger gene embedded within a complete genome, corresponding to the mitochondrial 16S rDNA of the stonefly Kamimuria wangi. Other Kamimuria mt genome regions are "regular", stressing unanswered questions on (a) swinger polymerization regulation; (b) swinger 16S rDNA functions; and (c) specificity to rDNA, in particular 16S rDNA. Sharp switches between regular and swinger replication, together with previous observations on swinger transcription, suggest that swinger replication might be due to a switch in polymerization mode of regular polymerases and the possibility of swinger-encoded information, predicted in primordial genes such as rDNA.
Nogales, Balbina; Moore, Edward R. B.; Llobet-Brossa, Enrique; Rossello-Mora, Ramon; Amann, Rudolf; Timmis, Kenneth N.
The bacterial diversity assessed from clone libraries prepared from rRNA (two libraries) and ribosomal DNA (rDNA) (one library) from polychlorinated biphenyl (PCB)-polluted soil has been analyzed. A good correspondence of the community composition found in the two types of library was observed. Nearly 29% of the cloned sequences in the rDNA library were identical to sequences in the rRNA libraries. More than 60% of the total cloned sequence types analyzed were grouped in phylogenetic groups (a clone group with sequence similarity higher than 97% [98% for Burkholderia and Pseudomonas-type clones]) represented in both types of libraries. Some of those phylogenetic groups, mostly represented by a single (or pair) of cloned sequence type(s), were observed in only one of the types of library. An important difference between the libraries was the lack of clones representative of the Actinobacteria in the rDNA library. The PCB-polluted soil exhibited a high bacterial diversity which included representatives of two novel lineages. The apparent abundance of bacteria affiliated to the beta-subclass of the Proteobacteria, and to the genus Burkholderia in particular, was confirmed by fluorescence in situ hybridization analysis. The possible influence on apparent diversity of low template concentrations was assessed by dilution of the RNA template prior to amplification by reverse transcription-PCR. Although differences in the composition of the two rRNA libraries obtained from high and low RNA concentrations were observed, the main components of the bacterial community were represented in both libraries, and therefore their detection was not compromised by the lower concentrations of template used in this study. PMID:11282645
Benga, Laurentiu; Benten, W Peter M; Engelhardt, Eva; Köhrer, Karl; Gougoula, Christina; Sager, Martin
Correct identification of bacteria is crucial for the management of rodent colonies. Some bacteria are difficult to identify phenotypically outside reference laboratories. In this study, we evaluated the utility of 16S ribosomal DNA (rDNA) sequencing as a means of identifying a collection of 30 isolates of rodent origin which are conventionally difficult to identify. Sequence analysis of the first approximate 720 to 880 bp of the 5'- end of 16S rDNA identified 25 isolates (83.33%) with ≥ 99% similarity to a sequence of a type strain, whereas three isolates (10%) displayed a sequence similarity ≥ 97% but <99% to the type strain sequences. These similarity scores were used to define identification to species and genus levels, respectively. Two of the 30 isolates (6.67%) displayed a sequence similarity of ≥ 95 but <97% to the reference strains and were thus allocated to a family. This technique allowed us to document the association of mice with bacteria relevant for the colonies management such as Pasteurellaceae, Bordetella hinzii or Streptococcus danieliae. In addition, human potential pathogens such as Acinetobacter spp., Ochrobactrum anthropi and Paracoccus yeei or others not yet reported in mouse bacterial species such as Leucobacter chironomi, Neisseria perflava and Pantoea dispersa were observed. In conclusion, the sequence analysis of 16S rDNA proved to be a useful diagnostic tool, with higher performance characteristics than the classical phenotypic methods, for identification of laboratory animal bacteria. For the first time this method allowed us to document the association of certain bacterial species with the laboratory mouse.
Takishita, Kiyotaka; Yubuki, Naoji; Kakizoe, Natsuki; Inagaki, Yuji; Maruyama, Tadashi
Recent culture-independent surveys of eukaryotic small-subunit ribosomal DNA (SSU rDNA) from many environments have unveiled unexpectedly high diversity of microbial eukaryotes (microeukaryotes) at various taxonomic levels. However, such surveys were most probably biased by various technical difficulties, resulting in underestimation of microeukaryotic diversity. In the present study on oxygen-depleted sediment from a deep-sea methane cold seep of Sagami Bay, Japan, we surveyed the diversity of eukaryotic rDNA in raw sediment samples and in two enrichment cultures. More than half of all clones recovered from the raw sediment samples were of the basidiomycetous fungus Cryptococcus curvatus. Among other clones, phylotypes of eukaryotic parasites, such as Apicomplexa, Ichthyosporea, and Phytomyxea, were identified. On the other hand, we observed a marked difference in phylotype composition in the enrichment samples. Several phylotypes belonging to heterotrophic stramenopiles were frequently found in one enrichment culture, while a phylotype of Excavata previously detected at a deep-sea hydrothermal vent dominated the other. We successfully established a clonal culture of this excavate flagellate. Since these phylotypes were not identified in the raw sediment samples, the approach incorporating a cultivation step successfully found at least a fraction of the "hidden" microeukaryotic diversity in the environment examined.
Lam, Katherine; Morton, Brian
Two sympatric species of Platygyra have been identified from Hong Kong waters: i.e., P. sinensis and P. pini. The former has been further subdivided into 4 morphotypes based on colony growth form as follows: classic, encrusting, hillocky, and long-valley. Taxonomic confusion raised by overlapping morphological variations and frequent sympatric occurrences, however, has posed problems in relation to Platygyra ecology and population dynamics. This study attempted to differentiate Platygyra pini and morphotypes of P. sinensis by both morphological and ITS1, 5.8S, and partial ITS2 ribosomal DNA sequence analysis. Morphological data based on 9 skeletal characters were subjected to multivariate analysis. No clear groupings were obtained using a multidimensional scaling plot. Most parsimony analysis was conducted using either the rDNA data set including ITS1, 5.8S, and partial ITS2 or the ITS1 region only. Maximum parsimony (MP) and neighbor-joining (NJ) trees obtained from both data sets, clustered samples of P. sinensis and P. pini into 2 clades. The interspecific Kimura 2-parameter sequence divergence value (k2) obtained by the former rDNA data set was 14.275 +/- 0.507%, which is greater than the intraspecific values (1.239 +/- 1.147% for P. sinensis and 0.469 +/- 0.364% for P. pini), indicating that this marker of ITS1, 5.8S, and ITS2 contains substantially high levels of inherent diversity and is useful in resolving the problematic taxonomy of Platygyra.
Xuan, Ying-hua; Cui, Chun-quan; Zheng, Shan-zi
The endosymbiont of Acanthamoeba sp. CB/SI was identified by orcein-carmine staining and 16S rDNA sequence analysis. The endosymbiont bacteria were rod-shaped and darkly stained, and irregularly localized within the cytoplasm. The length of the 16S rDNA was 1534 bp and its DNA sequence was closely related to those of Candidatus Amoebophilus asiaticus and Acanthamoeba sp. KA/E21 with 98% homology. Phylogenetic analysis showed that the endosymbiont of CB/SI, the endosymbiont of KA/E21, Candidatus Amoebophilus asiaticus, the endosymbiont of Ixodes scapularis, and the endosymbiont of Encarsia pergandiella constitute a monophyletic lineage in phylogenetic tree.
Oliveira, Claudio M. G.; Hübschen, Judith; Brown, Derek J. F.; Ferraz, Luiz C. C. B.; Wright, Frank; Neilson, Roy
Maximum likelihood trees produced from 18S rDNA sequences separated 14 Xiphinema and five Xiphidorus nematode species from Brazil into distinct groups that concurred with their current morphological taxonomic status. Species belonging to the X. americanum group (X. brevicolle, X. diffusum, X. oxycaudatum, and X. peruvianum) formed a single group that was clearly separated from the other Xiphinema species. As with previous taxonomic studies that noted only minor morphological differences between putative X. americanum group species, separation of these species based upon 18S rDNA sequences was inconclusive. Thus it is probable that instead of comprising distinct species, the X. americanum group may in fact represent numerous morphotypes with large inter- and intra- population morphological variability that may be environmentally driven. Within the cluster representing non X. americanum group species, there was little statistical support to clearly separate species. However, three subgroups, comprising (i) the X. setariae/vulgare complex, (ii) X. ifacolum and X. paritaliae, and (iii) X. brasiliense and X. ensiculiferum were well resolved. PMID:19262801
Chen, Juan; Xing, Xiao-Ke; Zhang, Li-Chun; Xing, Yong-Mei; Guo, Shun-Xing
Hortaea werneckii is a black yeast-like ascomycetous fungi associated with the human superficial infection tinea nigra, which commonly occurs in tropical and subtropical countries. Now, this fungus has been found in the halophilic environment all over the world and recognized as a new model organism in exploring the mechanisms of salt tolerance in eukaryotes. During a survey of endophytic fungi of mangrove forest at South China Sea, two isolates of H. werneckii were recovered from medicinal plant of Aegiceras comiculatum. The isolates were identified by morphological characters and phylogenetic analyses (e.g., ITS rDNA, LSU rDNA and translation elongation factor EF1α). Some physiological tests such as thermotolerance, acid tolerance (pH) and NaCl tolerance as well as pathogenicity test in vitro for the strains of Hortaea were performed. It is the first report that H. werneckii was isolated from medicinal plant of A. comiculatum in south sea of China as the endophytic fungi.
LaRue, Bernard; Gaudreau, Christine; Bagre, Hubert O; Charpentier, Guy
A sample of 15 Nearctic black fly species spread over five genera is used to perform the first systematic study of the internal transcribed spacer 1 (ITS1) from the nuclear rDNA transcription unit of Simuliidae. ITS1 from the Prosimuliini tribe is a conserved, repeat-free and highly structured sequence of about 490 nucleotides (nt), while Simuliini exhibit a medium-sized or short version, the latter minimally 95 nt long. All size versions possess a common 39 nt core made from eight short blocks interspersed among highly variable sequences. Conversely, that variability which generally excludes ITS1 from phylogenetic applications translates for many species into polymorphisms suggesting the general feasibility of ITS1-based population studies. We show in a parallel investigation that ITS2, the other rDNA transcribed spacer, is length-constrained around 270 nt and possesses a three-domain fold anchored by four conserved regions representing about 40% of the whole sequence. An alignment guided by this secondary structure leads to a phylogeny, derived through the GTR model, which convincingly displays the basal divergence between Simuliini and Prosimuliini. However, the poorer support of some intermediate nodes could indicate rapid divergence events within Simulium.
Rudi, Knut; Kleiberg, Gro H; Heiberg, Ragnhild; Rosnes, Jan T
The aim of this work was to evaluate restriction fragment melting curve analyses (RFMCA) as a novel approach for rapid classification of bacteria during food production. RFMCA was evaluated for bacteria isolated from sous vide food products, and raw materials used for sous vide production. We identified four major bacterial groups in the material analysed (cluster I-Streptococcus, cluster II-Carnobacterium/Bacillus, cluster III-Staphylococcus and cluster IV-Actinomycetales). The accuracy of RFMCA was evaluated by comparison with 16S rDNA sequencing. The strains satisfying the RFMCA quality filtering criteria (73%, n=57), with both 16S rDNA sequence information and RFMCA data (n=45) gave identical group assignments with the two methods. RFMCA enabled rapid and accurate classification of bacteria that is database compatible. Potential application of RFMCA in the food or pharmaceutical industry will include development of classification models for the bacteria expected in a given product, and then to build an RFMCA database as a part of the product quality control.
Liu, Z; Zhao, A; Chen, L; Pape, L
RNA polymerase I-catalyzed synthesis of the Schizosaccharomyces pombe approximately 37S pre-rRNAs was shown to be sensitive to regulatory sequences located several kilobases upstream of the initiation site for the rRNA gene. An in vitro transcription system for RNA polymerase I-catalyzed RNA synthesis was established that supports correct and activated transcription from templates bearing a full S. pombe rRNA gene promoter. A 780 bp region starting at -2560 significantly stimulates transcription of ac is-located rDNA promoter and competes with an rDNA promoter in trans, thus displaying some of the activities of rDNA transcriptional enhancers in vitro. Deletion of a 30 bp enhancer-homologous domain in this 780 bp far upstream region blocked its cis-stimulatory effect. The sequence of the S. pombe 3.5 kb intergenic spacer was determined and its organization differs from that of vertebrate, Drosophila, Acanthamoeba and plant intergenic rDNA spacers: it does not contain multiple, imperfect copies of the rRNA gene promoter nor repetitive elements of 140 bp, as are found in vertebrate rDNA enhancers. PMID:9016610
Naimuddin, Mohammed; Ohtsuka, Isao; Kitamura, Koichiro; Kudou, Motonori; Kimura, Shinnosuke
In vitro display technologies such as ribosome display and messenger RNA (mRNA)/complementary DNA (cDNA) display are powerful methods that can generate library diversities on the order of 10(10-14). However, in mRNA and cDNA display methods, the end use diversity is two orders of magnitude lower than initial diversity and is dependent on the downstream processes that act as limiting factors. We found that in our previous cDNA display protocol, the purification of protein fusions by the use of streptavidin matrices from cell-free translation mixtures had poor efficiency (∼10-15%) that seriously affected the diversity of the purified library. Here, we have investigated and optimized the protocols that provided remarkable purification efficiencies. The stalled ribosome in the mRNA-ribosome complex was found to impede this purification efficiency. Among the various conditions tested, destabilization of ribosomes by appropriate concentration of metal chelating agents in combination with an optimal temperature of 30°C were found to be crucial and effective for nearly complete isolation of protein fusions from the cell-free translation system. Thus, this protocol provided 8- to 10-fold increased efficiency of purification over the previous method and results in retaining the diversity of the library by approximately an order of magnitude-important for directed evolution. We also discuss the possible effects in the fabrication of protein chips.
High-throughput next-generation sequencing was used to scan the genome and generate reliable sequence of high copy number regions. Using this method, we examined whole plastid genomes as well as nearly 6000 bases of nuclear ribosomal DNA sequences for nine genotypes of Theobroma cacao and an indivi...
Jesuino, Rosália S A; Pereira, Maristela; Felipe, M Sueli S; Azevedo, Maristella O; Soares, Célia M A
A 630 bp cDNA encoding an L35 ribosomal protein of Paracoccidioides brasiliensis, designated as Pbl35, was cloned from a yeast expression library. Pbl35 encodes a polypeptide of 125 amino acids, with a predicted molecular mass of 14.5 kDa and a pI of 11.0. The deduced PbL35 shows significant conservation in respect to other described ribosomal L35 proteins from eukaryotes and prokaryotes. Motifs of ribosomal proteins are present in PbL35, including a bipartite nuclear localization signal (NLS) that could be related to the protein addressing to the nucleolus for the ribosomal assembly. The mRNA for PbL35, about 700 nucleotides in length, is expressed at a high level in P. brasiliensis. The PbL35 and the deduced amino acid sequence constitute the first description of a ribosomal protein in P. brasiliensis. The cDNA was deposited in GenBank under accession number AF416509.
Wada, R; Nakano, N; Yajima, N; Yoneyama, T; Wakasaya, Y; Murakami, C; Yamato, K; Yagihashi, S
A 57-year-old Japanese man complained of pain on micturition. The prostate was of normal size but hard. Transrectal needle biopsy demonstrated granulomatous prostatitis with small focal abscesses. Staining with periodic acid-Schiff, Grocott's methenamine silver and Fontana-Masson revealed yeast-form fungus in the granulomas. The mucoid capsule of the fungus stained with mucicarmine. PCR specific for cryptococcal 18S rDNA using DNA extracted from the pathological specimen was positive, and the sequence was homologous to Cryptococcus neoformans. A diagnosis of cryptococcal granulomatous prostatitis was made. The patient was then found to suffer from meningitis and lung abscess, and was treated with amphotericin B and flucytosine. Careful histological and molecular studies are beneficial to reach the correct diagnosis and to prevent an unfavorable outcome of disseminated cryptococcosis.
Kamstra, S A; Kuipers, A G; De Jeu, M J; Ramanna, M S; Jacobsen, E
Fluorescence in situ hybridization (FISH) was used to localise two species-specific repetitive DNA sequences, A001-I and D32-13, and two highly conserved 25S and 5S rDNA sequences on the metaphase chromosomes of two species of Alstroemeria. The Chilean species, Alstroemeria aurea (2n = 16), has abundant constitutive heterochromatin, whereas the Brazilian species, Alstroemeria inodora, has hardly any heterochromatin. The A. aurea specific A001-I probe hybridized specifically to the C-band regions on all chromosomes. The FISH patterns on A. inodora chromosomes using species-specific probe D32-13 resembled the C-banding pattern and the A001-I pattern on A. aurea chromosomes. There were notable differences in number and distribution of rDNA sites between the two species. The 25S rDNA probe revealed 16 sites in A. aurea that closely colocalised with A001-I sites and 12 in A. inodora that were predominantly detected in the centromeric regions. FISH karyotypes of the two Alstroemeria species were constructed accordingly, enabling full identification of all individual chromosomes. These FISH karyotypes will be useful for monitoring the chromosomes of both Alstroemeria species in hybrids and backcross derivatives.
Dingman, Douglas W
Failure to identify correctly the milky disease bacteria, Paenibacillus popilliae and Paenibacillus lentimorbus, has resulted in published research errors and commercial production problems. A DNA fingerprinting procedure, using PCR amplification of the 16S-23S rDNA intergenic transcribed spacer (ITS) regions, has been shown to easily and accurately identify isolates of milky disease bacteria. Using 34 P. popilliae and 15 P. lentimorbus strains, PCR amplification of different ITS regions produced three DNA fingerprints. For P. lentimorbus phylogenic group 2 strains and for all P. popilliae strains tested, electrophoresis of amplified DNA produced a migratory pattern (i.e., ITS-PCR fingerprint) exhibiting three DNA bands. P. lentimorbus group 1 strains also produced this ITS-PCR fingerprint. However, the fingerprint was phase-shifted toward larger DNA sizes. Alignment of the respective P. popilliae and P. lentimorbus group 1 ITS DNA sequences showed extensive homology, except for a 108bp insert in all P. lentimorbus ITS regions. This insert occurred at the same location relative to the 23S rDNA and accounted for the phase-shift difference in P. lentimorbus group 1 DNA fingerprints. At present, there is no explanation for this 108bp insert. The third ITS-PCR fingerprint, produced by P. lentimorbus group 3 strains, exhibited approximately eight DNA bands. Comparison of the three fingerprints of milky disease bacteria to the ITS-PCR fingerprints of other Paenibacillus species demonstrated uniqueness. ITS-PCR fingerprinting successfully identified eight unknown isolates as milky disease bacteria. Therefore, this procedure can serve as a standard protocol to identify P. popilliae and P. lentimorbus.
César Venere, Paulo; Thums Konerat, Jocicléia; Henrique Zawadzki, Cláudio; Ricardo Vicari, Marcelo; Margarido, Vladimir Pavan
Hypostomus is a diverse group with unclear aspects regarding its biology, including the mechanisms that led to chromosome diversification within the group. Fluorescence in situ hybridization (FISH) with 5S and 18S rDNA probes was performed on ten Hypostomini species. Hypostomus faveolus, H. cochliodon, H. albopunctatus, H. aff. paulinus, and H. topavae had only one chromosome pair with 18S rDNA sites, while H. ancistroides, H. commersoni, H. hermanni, H. regani, and H. strigaticeps had multiple 18S rDNA sites. Regarding the 5S rDNA genes, H. ancistroides, H. regani, H. albopunctatus, H. aff. paulinus, and H. topavae had 5S rDNA sites on only one chromosome pair and H. faveolus, H. cochliodon, H. commersoni, H. hermanni, and H. strigaticeps had multiple 5S rDNA sites. Most species had 18S rDNA sites in the telomeric region of the chromosomes. All species but H. cochliodon had 5S rDNA in the centromeric/pericentromeric region of one metacentric pair. Obtained results are discussed based on existent phylogenies for the genus, with comments on possible dispersion mechanisms to justify the variability of the rDNA sites in Hypostomus. PMID:25405240
Bueno, Vanessa; Venere, Paulo César; Thums Konerat, Jocicléia; Zawadzki, Cláudio Henrique; Vicari, Marcelo Ricardo; Margarido, Vladimir Pavan
Hypostomus is a diverse group with unclear aspects regarding its biology, including the mechanisms that led to chromosome diversification within the group. Fluorescence in situ hybridization (FISH) with 5S and 18S rDNA probes was performed on ten Hypostomini species. Hypostomus faveolus, H. cochliodon, H. albopunctatus, H. aff. paulinus, and H. topavae had only one chromosome pair with 18S rDNA sites, while H. ancistroides, H. commersoni, H. hermanni, H. regani, and H. strigaticeps had multiple 18S rDNA sites. Regarding the 5S rDNA genes, H. ancistroides, H. regani, H. albopunctatus, H. aff. paulinus, and H. topavae had 5S rDNA sites on only one chromosome pair and H. faveolus, H. cochliodon, H. commersoni, H. hermanni, and H. strigaticeps had multiple 5S rDNA sites. Most species had 18S rDNA sites in the telomeric region of the chromosomes. All species but H. cochliodon had 5S rDNA in the centromeric/pericentromeric region of one metacentric pair. Obtained results are discussed based on existent phylogenies for the genus, with comments on possible dispersion mechanisms to justify the variability of the rDNA sites in Hypostomus.
Urano, Y; Kominami, R; Mishima, Y; Muramatsu, M
Approximately one kilobase pairs surrounding and upstream the transcription initiation site of a cloned ribosomal DNA (rDNA) of the mouse were sequenced. The putative transcription initiation site was determined by two independent methods: one nuclease S1 protection and the other reverse transcriptase elongation mapping using isolated 45S ribosomal RNA precursor (45S RNA) and appropriate restriction fragments of rDNA. Both methods gave an identical result; 45S RNA had a structure starting from ACTCTTAG---. Characteristically, mouse rDNA had many T clusters (greater than or equal to 5) upstream the initiation site, the longest being 21 consecutive T's. A pentadecanucleotide, TGCCTCCCGAGTGCA, appeared twice within 260 nucleotides upstream the putative initiation site. No such characteristic sequences were found downstream this site. Little similarity was found in the upstream of the transcription initiation site between the mouse, Xenopus laevis and Saccharomyces cerevisiae rDNA. Images PMID:6162156
Sakthivelkumar, S; Ramaraj, P; Veeramani, V; Janarthanan, S
The basis of the present study was to distinguish the existence of any genetic variability among populations of Culex quinquefasciatus which would be a valuable tool in the management of mosquito control programmes. In the present study, population of Cx. quinquefasciatus collected at different locations in Tamil Nadu were analyzed for their genetic variation based on 28S rDNA D2 region nucleotide sequences. A high degree of genetic polymorphism was detected in the sequences of D2 region of 28S rDNA on the predicted secondary structures in spite of high nucleotide sequence similarity. The findings based on secondary structure using rDNA sequences suggested the existence of a complex genotypic diversity of Cx. quinquefasciatus population collected at different locations of Tamil Nadu, India. This complexity in genetic diversity in a single mosquito population collected at different locations is considered an important issue towards their influence and nature of vector potential of these mosquitoes.
Yang, Hye-Won; Lee, Yu-Ran; Inoue, Noboru; Jha, Bijay Kumar; Danne, Dinzouna-Boutamba Sylvatrie; Kim, Hong-Kyun; Lee, Junhun; Goo, Youn-Kyoung; Kong, Hyun-Hee; Chung, Dong-Il; Hong, Yeonchul
Amoebic keratitis (AK) caused by Acanthamoeba is one of the most serious corneal infections. AK is frequently misdiagnosed initially as viral, bacterial, or fungal keratitis, thus ensuring treatment delays. Accordingly, the early detection of Acanthamoeba would contribute significantly to disease management and selection of an appropriate anti-amoebic therapy. Recently, the loop-mediated isothermal amplification (LAMP) method has been applied to the clinical diagnosis of a range of infectious diseases. Here, we describe a rapid and efficient LAMP-based method targeting Acanthamoeba 18S rDNA gene for the detection of Acanthamoeba using clinical ocular specimens in the diagnosis of AK. Acanthamoeba LAMP assays detected 11 different strains including all AK-associated species. The copy number detection limit for a positive signal was 10 DNA copies of 18S rDNA per reaction. No cross-reactivity with the DNA of fungi or other protozoa was observed. The sensitivity of LAMP assay was higher than those of Nelson primer PCR and JDP primer PCR. In the present study, LAMP assay based on directly heat-treated samples was found to be as efficient at detecting Acanthamoeba as DNA extracted using a commercial kit, whereas PCR was only effective when commercial kit-extracted DNA was used. This study showed that the devised Acanthamoeba LAMP assay could be used to diagnose AK in a simple, sensitive, and specific manner.
Yang, Hye-Won; Lee, Yu-Ran; Inoue, Noboru; Jha, Bijay Kumar; Danne, Dinzouna-Boutamba Sylvatrie; Kim, Hong-Kyun; Lee, Junhun; Goo, Youn-Kyoung; Kong, Hyun-Hee; Chung, Dong-Il
Amoebic keratitis (AK) caused by Acanthamoeba is one of the most serious corneal infections. AK is frequently misdiagnosed initially as viral, bacterial, or fungal keratitis, thus ensuring treatment delays. Accordingly, the early detection of Acanthamoeba would contribute significantly to disease management and selection of an appropriate anti-amoebic therapy. Recently, the loop-mediated isothermal amplification (LAMP) method has been applied to the clinical diagnosis of a range of infectious diseases. Here, we describe a rapid and efficient LAMP-based method targeting Acanthamoeba 18S rDNA gene for the detection of Acanthamoeba using clinical ocular specimens in the diagnosis of AK. Acanthamoeba LAMP assays detected 11 different strains including all AK-associated species. The copy number detection limit for a positive signal was 10 DNA copies of 18S rDNA per reaction. No cross-reactivity with the DNA of fungi or other protozoa was observed. The sensitivity of LAMP assay was higher than those of Nelson primer PCR and JDP primer PCR. In the present study, LAMP assay based on directly heat-treated samples was found to be as efficient at detecting Acanthamoeba as DNA extracted using a commercial kit, whereas PCR was only effective when commercial kit-extracted DNA was used. This study showed that the devised Acanthamoeba LAMP assay could be used to diagnose AK in a simple, sensitive, and specific manner. PMID:23864737
Weiss-Schneeweiss, Hanna; Tremetsberger, Karin; Schneeweiss, Gerald M.; Parker, John S.; Stuessy, Tod F.
Background and Aims Changes in chromosome structure and number play an important role in plant evolution. A system well-suited to studying different modes of chromosome evolution is the genus Hypochaeris (Asteraceae) with its centre of species' diversity in South America. All South American species uniformly have a chromosome base number of x = 4 combined with variation in rDNA number and distribution, and a high frequency of polyploidy. The aim of this paper is to assess directions and mechanisms of karyotype evolution in South American species by interpreting both newly obtained and previous data concerning rDNA localization in a phylogenetic context. Methods Eleven Hypochaeris species from 18 populations were studied using fluorescence in situ hybridization (FISH) with 35S and 5S rDNA probes. A phylogenetic framework was established from neighbour-net analysis of amplified fragment length polymorphism (AFLP) fingerprint data. Key Results A single 5S rDNA locus is invariably found on the short arm of chromosome 2. Using 35S rDNA loci, based on number (one or two) and localization (interstitial on the long arm of chromosome 2, but sometimes lacking, and terminal or interstitial on the short arm of chromosome 3, only very rarely lacking), seven karyotype groups can be distinguished; five of these include polyploids. Karyotype groups with more than one species do not form monophyletic groups. Conclusions Early evolution of Hypochaeris in South America was characterized by considerable karyotype differentiation resulting from independent derivations from an ancestral karyotype. There was marked diversification with respect to the position and evolution of the 35S rDNA locus on chromosome 3, probably involving inversions and/or transpositions, and on chromosome 2 (rarely 3) concerning inactivation and loss. Among these different karyotype assemblages, the apargioides group and its derivatives constitute by far the majority of species. PMID:18285356
Nashimoto, M; Mishima, Y
Based on recent experimental data about transcription initiation and termination, a model for regulation of mammalian ribosomal DNA transcription is developed using a simple kinetic scheme. In this model, the existence of the transition pathway from the terminator to the promoter increases the rate of ribosomal RNA precursor synthesis. In addition to this 'non-transcribed spacer' traverse of RNA polymerase I, the co-ordination of initiation and termination allows a rapid on/off switch transition from the minimum to the maximum rate of ribosomal RNA precursor synthesis. Furthermore, taking account of the participation of two factors in the termination event, we propose a plausible molecular mechanism for the co-ordination of initiation and termination. This co-ordination is emphasized by repetition of the terminator unit. PMID:3223915
Raadsma, H W; O'Meara, T J; Egerton, J R; Lehrbach, P R; Schwartzkoff, C L
The relationship between K-agglutination antibody titres and protection against experimental challenge with Dichelobacter nodosus, the effect of increasing the number of D. nodosus fimbrial antigens, and the importance of the nature of additional antigens in multivalent vaccines on antibody response and protection against experimental challenge with D. nodosus were examined in Merino sheep. A total of 204 Merino sheep were allocated to one of 12 groups, and vaccinated with preparations containing a variable number of rDNA D. nodosus fimbrial antigens. The most complex vaccine contained ten fimbrial antigens from all major D. nodosus serogroups, while the least complex contained a single fimbrial antigen. In addition to D. nodosus fimbrial antigens, other bacterial rDNA fimbrial antigens (Moraxella bovis Da12d and Escherichia coli K99), and bovine serum albumin (BSA) were used in some vaccines. Antibody titres to fimbrial antigens and BSA were measured by agglutination and ELISA tests, respectively. Antibody titres were determined on five occasions (Weeks 0, 3, 6, 8, and 11 after primary vaccination). All sheep were exposed to an experimental challenge with virulent isolates of D. nodosus from either serogroup A or B, 8 weeks after primary vaccination. For D. nodosus K-agglutinating antibody titres, a strong negative correlation between antibody titre and footrot lesion score was observed. This relationship was influenced by the virulence of the challenge strain. Increasing the number of fimbrial antigens in experimental rDNA D. nodosus fimbrial vaccines resulted in a linear decrease in K-agglutinating antibody titres to individual D. nodosus serogroups. Similarly, a linear decrease in protection to challenge with homologous serogroups was observed as the number of D. nodosus fimbrial antigens represented in the vaccine increased. The reduction in antibody titres in multicomponent vaccines is thought to be due to antigenic competition. The level of competition
Takahashi, Hajime; Kimura, Bon; Tanaka, Yuichiro; Mori, Mayumi; Yokoi, Asami; Fujii, Tateo
The grouping method for isolated strains from foods using single-strand conformation polymorphism (SSCP) after PCR amplification of a portion of 16S rDNA was developed. This method was able to group the strains from various food samples based on 16S rDNA sequence. As 97.8% of the isolated strains from various foods were grouped correctly, use of the PCR-SSCP method enables the prompt and labor-saving analysis of microbial population of food-derived bacterial strains. Advantages in speed and accuracy of bacterial population identification by the PCR-SSCP method have practical application for food suppliers and testing laboratories.
Atibalentja, N.; Noel, G. R.; Ciancio, A.
For many years the taxonomy of the genus Pasteuria has been marred with confusion because the bacterium could not be cultured in vitro and, therefore, descriptions were based solely on morphological, developmental, and pathological characteristics. The current study sought to devise a simple method for PCR-amplification, cloning, and sequencing of Pasteuria 16S rDNA from small numbers of endospores, with no need for prior DNA purification. Results show that DNA extracts from plain glass bead-beating of crude suspensions containing 10,000 endospores at 0.2 × 10⁶ endospores ml-1 were sufficient for PCR-amplification of Pasteuria 16S rDNA, when used in conjunction with specific primers. These results imply that for P. penetrans and P. nishizawae only one parasitized female of Meloidogyne spp. and Heterodera glycines, respectively, should be sufficient, and as few as eight cadavers of Belonolaimus longicaudatus with an average number of 1,250 endospores of "Candidatus Pasteuria usgae" are needed for PCR-amplification of Pasteuria 16S rDNA. The method described in this paper should facilitate the sequencing of the 16S rDNA of the many Pasteuria isolates that have been reported on nematodes and, consequently, expedite the classification of those isolates through comparative sequence analysis. PMID:19262793
Henriques, M; Sá-Nogueira, I; Giménez-Jurado, G; van Uden, N
To test whether DNA probes derived from ribosomal DNA spacer sequences are suitable for rapid and species-specific yeast identification, a pilot study was undertaken. A 7.7 kb entire ribosomal DNA unit of the type strain of Metschnikowia reukaufii was isolated, cloned and mapped. A 0.65 kb BamHI-HpaI fragment containing non-transcribed spacer sequences was amplified and selected for testing as a 32P hybridization probe with total DNA from the type strains of M. reukaufii, M. pulcherrima, M. lunata, M. bicuspidata, M. australis, M. zobellii, M. krissii, five other strains identified as M. reukaufii and strains of Schizosaccharomyces pombe, Hansenula canadensis, Saccharomyces cerevisiae and Yarrowia lipolytica. The probe hybridized exclusively with DNA from the type strain and four other strains of M. reukaufii. DNA from one strain labelled M. reukaufii did not hybridize with the probe. Subsequent % G + C comparison and DNA-DNA reassociation with the type strain revealed that the non-hybridizing strain does not belong to the species M. reukaufii.
Yilmaz, Fadime; Orman, Nazlı; Serim, Gamze; Kochan, Ceren; Ergene, Aysun; Icgen, Bulent
Four Staphylococcus isolates having both multidrug- and multimetal-resistant ability were isolated from surface water. Further identification of the isolates was obtained through biochemical tests and 16S rDNA gene sequencing. One methicillin-resistant and two methicillin-sensitive isolates were determined as Staphylococcus aureus. The other isolate was identified as Staphylococcus warneri. The antibiotic and heavy metal resistance profiles of the Staphylococcus isolates were determined by using 26 antibiotics and 17 heavy metals. S. aureus isolates displayed resistance to most of the β-lactam antibiotics tested. All Staphylococcus isolates were resistant to heavy metals including silver, lithium, and barium. Due to a possible health risk of these pathogenic bacteria, a need exists for an accurate assessment of their acquired resistance to multiple drugs and metals.
Oyhenart, Jorge; Martínez, Florencia; Ramírez, Rosana; Fort, Marcelo; Breccia, Javier D
Tritrichomonas foetus is the causative agent of bovine trichomonosis, a sexually transmitted disease leading to infertility and abortion. A test based on loop mediated isothermal amplification (LAMP) targeting the 5.8S rDNA subunit was designed for the specific identification of T. foetus. The LAMP assay was validated using 28 T. foetus and 35 non-T. foetus trichomonads strains. It did not exhibit cross-reaction with closely related parasites commonly found in smegma cultures like Tetratrichomonas spp. and Pentatrichomonas hominis. Bovine smegma did not show interferences for the detection of the parasite and, the sensitivity of the method (4×10(3) CFU/mL, approximately 10 cells/reaction) was slightly higher than that found for PCR amplification with TFR3 and TFR4 primers. The LAMP approach has potential applications for diagnosis and control of T. foetus and, practical use for low skill operators in rural areas.
Aguilera, Patricia M; Debat, Humberto J; Scaldaferro, Marisel A; Martí, Dardo A; Grabiele, Mauro
We present here the physical mapping of the 5S rDNA locus in six wild and five cultivated taxa of Capsicum by means of a genus-specific FISH probe. In all taxa, a single 5S locus per haploid genome that persistently mapped onto the short arm of a unique metacentric chromosome pair at intercalar position, was found. 5S FISH signals of almost the same size and brightness intensity were observed in all the analyzed taxa. This is the first cytological characterization of the 5S in wild taxa of Capsicum by using a genus-derived probe, and the most exhaustive and comprehensive in the chili peppers up to now. The information provided here will aid the cytomolecular characterization of pepper germplasm to evaluate variability and can be instrumental to integrate physical, genetic and genomic maps already generated in the genus.
Beckers, Bram; Op De Beeck, Michiel; Thijs, Sofie; Truyens, Sascha; Weyens, Nele; Boerjan, Wout; Vangronsveld, Jaco
Next-generation sequencing technologies have revolutionized the methods for studying microbial ecology by enabling high-resolution community profiling. However, the use of these technologies in unraveling the plant microbiome remains challenging. Many bacterial 16S rDNA primer pairs also exhibit high affinity for non-target DNA such as plastid (mostly chloroplast) DNA and mitochondrial DNA. Therefore, we experimentally tested a series of commonly used primers for the analysis of plant-associated bacterial communities using 454 pyrosequencing. We evaluated the performance of all selected primer pairs in the study of the bacterial microbiomes present in the rhizosphere soil, root, stem and leaf endosphere of field-grown poplar trees (Populus tremula × Populus alba) based on (a) co-amplification of non-target DNA, (b) low amplification efficiency for pure chloroplast DNA (real-time PCR), (c) high retrieval of bacterial 16S rDNA, (d) high operational taxonomic unit (OTU) richness and Inverse Simpson diversity and (e) taxonomic assignment of reads. Results indicate that experimental evaluation of primers provide valuable information that could contribute in the selection of suitable primer pairs for 16S rDNA metabarcoding studies in plant-microbiota research. Furthermore, we show that primer pair 799F-1391R outperforms all other primer pairs in our study in the elimination of non-target DNA and retrieval of bacterial OTUs. PMID:27242686
Padgett, D J; Les, D H; Crow, G E
The genus Nuphar consists of yellow-flowered waterlilies and is widely distributed in north-temperate bodies of water. Despite regular taxonomic evaluation of these plants, no explicit phylogenetic hypotheses have been proposed for the genus. We investigated phylogenetic relationships in Nuphar using morphology and sequences of the chloroplast gene matK and of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA. Two major lineages within Nuphar are consistently resolved with the morphological and molecular data sets. One lineage comprises New World taxa and the other represents a primarily Old World lineage. Relationships within the major lineages were poorly resolved by morphology and ITS, yet certain relationships were elucidated by all analyses. Most notable is the strong support for a monophyletic lineage of dwarf taxa and the alliance of the North American N. microphylla with the Eurasian taxa. Minor discordance between the independent cladograms is accounted for by hybridization. The common taxonomic practice of uniting all North American and Eurasian taxa under one species is not supported phylogenetically.
Hejazi, Mohammad A; Barzegari, Abolfazl; Gharajeh, Nahid Hosseinzadeh; Hejazi, Mohammad S
Comparison of 18S rDNA gene sequences is a very promising method for identification and classification of living organisms. Molecular identification and discrimination of different Dunaliella species were carried out based on the size of 18S rDNA gene and, number and position of introns in the gene. Three types of 18S rDNA structure have already been reported: the gene with a size of ~1770 bp lacking any intron, with a size of ~2170 bp consisting one intron near 5' terminus, and with a size of ~2570 bp harbouring two introns near 5' and 3' termini. Hereby, we report a new 18S rDNA gene arrangement in terms of intron localization and nucleotide sequence in a Dunaliella isolated from Iranian salt lakes (ABRIINW-M1/2). PCR amplification with genus-specific primers resulted in production of a ~2170 bp DNA band, which is similar to that of D. salina 18S rDNA gene containing only one intron near 5' terminus. Whilst, sequence composition of the gene revealed the lack of any intron near 5' terminus in our isolate. Furthermore, another alteration was observed due to the presence of a 440 bp DNA fragment near 3' terminus. Accordingly, 18S rDNA gene of the isolate is clearly different from those of D. salina and any other Dunaliella species reported so far. Moreover, analysis of ITS region sequence showed the diversity of this region compared to the previously reported species. 18S rDNA and ITS sequences of our isolate were submitted with accesion numbers of EU678868 and EU927373 in NCBI database, respectively. The optimum growth rate of this isolate occured at the salinity level of 1 M NaCl. The maximum carotenoid content under stress condition of intense light (400 mumol photon m-2 s-1), high salinity (4 M NaCl) and deficiency of nitrate and phosphate nutritions reached to 240 ng/cell after 15 days.
Honisch, M; Krone, O
A total of 153 free-ranging birds from Germany belonging to 15 species were examined for nematodes in their digestive and respiratory tracts. In 51.7% of the birds 14 different nematode species were found: the intestinal ascarids Porrocaecum depressum and P. angusticolle, the strongylid Hovorkonema variegatum, which inhabits the trachea and bronchi, the hairworms Eucoleus dispar and Capillaria tenuissima isolated from the digestive system, the spirurid nematodes Cyrnea leptoptera, C. mansioni, C. seurati, Microtetrameres cloacitectus, Physaloptera alata, P. apivori, Synhimantus hamatus and S. laticeps, which inhabit the proventriculus and gizzard of the raptors, and the spirurid nematode Serratospiculum tendo, which lives in the air sacs. To revise their systematic positions the ribosomal 18S gene regions of the nematode species were analysed and a phylogenetic tree was constructed. The molecular data confirmed the morphological systematics, except the spirurid family Physalopteridae, which grouped together with the Acuariidae.
Chauhan, Kanika; Dhakal, Rajat; Seale, R Brent; Deeth, Hilton C; Pillidge, Christopher J; Powell, Ian B; Craven, Heather; Turner, Mark S
Due to their ubiquity in the environment and ability to survive heating processes, sporeforming bacteria are commonly found in foods. This can lead to product spoilage if spores are present in sufficient numbers and where storage conditions favour spore germination and growth. A rapid method to identify the major aerobic sporeforming groups in dairy products, including Bacillus licheniformis group, Bacillus subtilis group, Bacillus pumilus group, Bacillus megaterium, Bacillus cereus group, Geobacillus species and Anoxybacillus flavithermus was devised. This method involves real-time PCR and high resolution melt analysis (HRMA) of V3 (~70 bp) and V6 (~100 bp) variable regions in the 16S rDNA. Comparisons of HRMA curves from 194 isolates of the above listed sporeforming bacteria obtained from dairy products which were identified using partial 16S rDNA sequencing, allowed the establishment of criteria for differentiating them from each other and several non-sporeforming bacteria found in samples. A blinded validation trial on 28 bacterial isolates demonstrated complete accuracy in unambiguous identification of the 7 different aerobic sporeformers. The reliability of HRMA method was also verified using boiled extractions of crude DNA, thereby shortening the time needed for identification. The HRMA method described in this study provides a new and rapid approach to identify the dominant mesophilic and thermophilic aerobic sporeforming bacteria found in a wide variety of dairy products.
Woo, P C Y; Lau, S K P; Teng, J L L; Tse, H; Yuen, K-Y
In the last decade, as a result of the widespread use of PCR and DNA sequencing, 16S rDNA sequencing has played a pivotal role in the accurate identification of bacterial isolates and the discovery of novel bacteria in clinical microbiology laboratories. For bacterial identification, 16S rDNA sequencing is particularly important in the case of bacteria with unusual phenotypic profiles, rare bacteria, slow-growing bacteria, uncultivable bacteria and culture-negative infections. Not only has it provided insights into aetiologies of infectious disease, but it also helps clinicians in choosing antibiotics and in determining the duration of treatment and infection control procedures. With the use of 16S rDNA sequencing, 215 novel bacterial species, 29 of which belong to novel genera, have been discovered from human specimens in the past 7 years of the 21st century (2001-2007). One hundred of the 215 novel species, 15 belonging to novel genera, have been found in four or more subjects. The largest number of novel species discovered were of the genera Mycobacterium (n = 12) and Nocardia (n = 6). The oral cavity/dental-related specimens (n = 19) and the gastrointestinal tract (n = 26) were the most important sites for discovery and/or reservoirs of novel species. Among the 100 novel species, Streptococcus sinensis, Laribacter hongkongensis, Clostridium hathewayi and Borrelia spielmanii have been most thoroughly characterized, with the reservoirs and routes of transmission documented, and S. sinensis, L. hongkongensis and C. hathewayi have been found globally. One of the greatest hurdles in putting 16S rDNA sequencing into routine use in clinical microbiology laboratories is automation of the technology. The only step that can be automated at the moment is input of the 16S rDNA sequence of the bacterial isolate for identification into one of the software packages that will generate the result of the identity of the isolate on the basis of its sequence database. However
Lindner, Daniel L; Carlsen, Tor; Henrik Nilsson, R; Davey, Marie; Schumacher, Trond; Kauserud, Håvard
The rDNA internal transcribed spacer (ITS) region has been accepted as a DNA barcoding marker for fungi and is widely used in phylogenetic studies; however, intragenomic ITS variability has been observed in a broad range of taxa, including prokaryotes, plants, animals, and fungi, and this variability has the potential to inflate species richness estimates in molecular investigations of environmental samples. In this study 454 amplicon pyrosequencing of the ITS1 region was applied to 99 phylogenetically diverse axenic single-spore cultures of fungi (Dikarya: Ascomycota and Basidiomycota) to investigate levels of intragenomic variation. Three species (one Basidiomycota and two Ascomycota), in addition to a positive control species known to contain ITS paralogs, displayed levels of molecular variation indicative of intragenomic variation; taxon inflation due to presumed intragenomic variation was ≈9%. Intragenomic variability in the ITS region appears to be widespread but relatively rare in fungi (≈3-5% of species investigated in this study), suggesting this problem may have minor impacts on species richness estimates relative to PCR and/or pyrosequencing errors. Our results indicate that 454 amplicon pyrosequencing represents a powerful tool for investigating levels of ITS intragenomic variability across taxa, which may be valuable for better understanding the fundamental mechanisms underlying concerted evolution of repetitive DNA regions.
Lindner, Daniel L; Carlsen, Tor; Henrik Nilsson, R; Davey, Marie; Schumacher, Trond; Kauserud, Håvard
The rDNA internal transcribed spacer (ITS) region has been accepted as a DNA barcoding marker for fungi and is widely used in phylogenetic studies; however, intragenomic ITS variability has been observed in a broad range of taxa, including prokaryotes, plants, animals, and fungi, and this variability has the potential to inflate species richness estimates in molecular investigations of environmental samples. In this study 454 amplicon pyrosequencing of the ITS1 region was applied to 99 phylogenetically diverse axenic single-spore cultures of fungi (Dikarya: Ascomycota and Basidiomycota) to investigate levels of intragenomic variation. Three species (one Basidiomycota and two Ascomycota), in addition to a positive control species known to contain ITS paralogs, displayed levels of molecular variation indicative of intragenomic variation; taxon inflation due to presumed intragenomic variation was ≈9%. Intragenomic variability in the ITS region appears to be widespread but relatively rare in fungi (≈3–5% of species investigated in this study), suggesting this problem may have minor impacts on species richness estimates relative to PCR and/or pyrosequencing errors. Our results indicate that 454 amplicon pyrosequencing represents a powerful tool for investigating levels of ITS intragenomic variability across taxa, which may be valuable for better understanding the fundamental mechanisms underlying concerted evolution of repetitive DNA regions. PMID:23789083
Waminal, Nomar Espinosa; Ryu, Ki Hyun; Choi, Sun-Hee; Kim, Hyun Hee
Monitoring of genetically modified (GM) crops has been emphasized to prevent their potential effects on the environment and human health. Monitoring of the inadvertent dispersal of transgenic maize in several fields and transport routes in Korea was carried out by qualitative multiplex PCR, and molecular analyses were conducted to identify the events of the collected GM maize. Cytogenetic investigations through fluorescence in situ hybridization (FISH) of the GM maize were performed to check for possible changes in the 45S rDNA cluster because this cluster was reported to be sensitive to replication and transcription stress. Three GM maize kernels were collected from a transport route near Incheon port, Korea, and each was found to contain NK603, stacked MON863 x NK603, and stacked NK603 x MON810 inserts, respectively. Cytogenetic analysis of the GM maize containing the stacked NK603 x MON810 insert revealed two normal compact 5S rDNA signals, but the 45S rDNA showed a fragile phenotype, demonstrating a "beads-on-a-string" fragmentation pattern, which seems to be a consequence of genetic modification. Implications of the 45S rDNA cluster fragility in GM maize are also discussed.
Guo, Liliang; Sui, Zhenghong; Liu, Yuan
Miseq sequencing and data analysis for the actin gene and v9 region of 18S rDNA of 7 simulated samples consisting of different mixture of dinoflagellates and diatoms were carried out. Not all the species were detectable in all the 18S v9 samples, and sequence percent in all the v9 samples were not consistent with the corresponding cell percent which may suggest that 18S rDNA copy number in different cells of these species differed greatly which result in the large deviation of the amplification. And 18S rDNA amplification of the microalgae was prone to be contaminated by fungus. The amplification of actin gene all was from the dinoflagellates because of its targeted degenerate primers. All the actin sequences of dinoflagellates were detected in the act samples except act4, and sequence percentage of the dinoflagellates in the act samples was not completely consistent with the dinoflagellates percentage of cell samples, but with certain amplification deviations. Indexes of alpha diversity of actin gene sequencing may be better reflection of community structure, and beta diversity analysis could cluster the dinoflagellates samples with identical or similar composition together and was distinguishable with blooming simulating samples at the generic level. Hence, actin gene was more proper than rDNA as the molecular marker for the community analysis of the dinoflagellates. PMID:27721499
Lin, Zhongheng; Shen, Songdong; Chen, Weizhou; Li, Huihui
Chlorophyta species are common in the southern and northern coastal areas of China. In recent years, frequent green tide incidents in Chinese coastal waters have raised concerns and attracted the attention of scientists. In this paper, we sequenced the 18S rDNA genes, the internal transcribed spacer (ITS) regions and the rbc L genes in seven organisms and obtained 536-566 bp long ITS sequences, 1 377-1 407 bp long rbc L sequences and 1 718-1 761 bp long partial 18S rDNA sequences. The GC base pair content was highest in the ITS regions and lowest in the rbc L genes. The sequencing results showed that the three Ulva prolifera (or U. pertusa) gene sequences from Qingdao and Nan'ao Island were identical. The ITS, 18S rDNA and rbc L genes in U. prolifera and U. pertusa from different sea areas in China were unchanged by geographic distance. U. flexuosa had the least evolutionary distance from U. californica in both the ITS regions (0.009) and the 18S rDNA (0.002). These data verified that Ulva and Enteromorpha are not separate genera.
Amorim, Karlla Danielle Jorge; Cioffi, Marcelo de Bello; Bertollo, Luiz Antonio Carlos; Soares, Rodrigo Xavier; de Souza, Allyson Santos; da Costa, Gideão Wagner Werneck Felix; Molina, Wagner Franco
Abstract Wrasses (Labridae) are extremely diversified marine fishes, whose species exhibit complex interactions with the reef environment. They are widely distributed in the Indian, Pacific and Atlantic oceans. Their species have displayed a number of karyotypic divergent processes, including chromosomal regions with complex structural organization. Current cytogenetic information for this family is phylogenetically and geographically limited and mainly based on conventional cytogenetic techniques. Here, the distribution patterns of heterochromatin, GC-specific chromosome regions and Ag-NORs, and the organization of 18S and 5S rDNA sites of the Atlantic species Thalassoma noronhanum (Boulenger, 1890), Halichoeres poeyi (Steindachner, 1867), Halichoeres radiatus (Linnaeus, 1758), Halichoeres brasiliensis (Bloch, 1791) and Halichoeres penrosei Starks, 1913, belonging to the tribe Julidini were analyzed. All the species exhibited 2n=48 chromosomes with variation in the number of chromosome arms among genera. Thalassoma noronhanum has 2m+46a, while species of the genus Halichoeres Rüppell, 1835 share karyotypes with 48 acrocentric chromosomes. The Halichoeres species exhibit differences in the heterochromatin distribution patterns and in the number and distribution of 18S and 5S rDNA sites. The occurrence of 18S/5S rDNA syntenic arrangements in all the species indicates a functionally stable and adaptive genomic organization. The phylogenetic sharing of this rDNA organization highlights a marked and unusual chromosomal singularity inside the family Labridae. PMID:28123678
Logares, Ramiro; Sunagawa, Shinichi; Salazar, Guillem; Cornejo-Castillo, Francisco M; Ferrera, Isabel; Sarmento, Hugo; Hingamp, Pascal; Ogata, Hiroyuki; de Vargas, Colomban; Lima-Mendez, Gipsi; Raes, Jeroen; Poulain, Julie; Jaillon, Olivier; Wincker, Patrick; Kandels-Lewis, Stefanie; Karsenti, Eric; Bork, Peer; Acinas, Silvia G
Sequencing of 16S rDNA polymerase chain reaction (PCR) amplicons is the most common approach for investigating environmental prokaryotic diversity, despite the known biases introduced during PCR. Here we show that 16S rDNA fragments derived from Illumina-sequenced environmental metagenomes (mi tags) are a powerful alternative to 16S rDNA amplicons for investigating the taxonomic diversity and structure of prokaryotic communities. As part of the Tara Oceans global expedition, marine plankton was sampled in three locations, resulting in 29 subsamples for which metagenomes were produced by shotgun Illumina sequencing (ca. 700 Gb). For comparative analyses, a subset of samples was also selected for Roche-454 sequencing using both shotgun (m454 tags; 13 metagenomes, ca. 2.4 Gb) and 16S rDNA amplicon (454 tags; ca. 0.075 Gb) approaches. Our results indicate that by overcoming PCR biases related to amplification and primer mismatch, mi tags may provide more realistic estimates of community richness and evenness than amplicon 454 tags. In addition, mi tags can capture expected beta diversity patterns. Using mi tags is now economically feasible given the dramatic reduction in high-throughput sequencing costs, having the advantage of retrieving simultaneously both taxonomic (Bacteria, Archaea and Eukarya) and functional information from the same microbial community.
Bhowmick, Biplab Kumar; Yamamoto, Masashi; Jha, Sumita
Coccinia grandis is a widely distributed dioecious cucurbit in India, with heteromorphic sex chromosomes and X-Y sex determination mode. The present study aids in the cytogenetic characterization of four native populations of this plant employing distribution patterns of 45S rDNA on chromosomes and guanine-cytosine (GC)-rich heterochromatin in the genome coupled with flow cytometric determination of genome sizes. Existence of four nucleolar chromosomes could be confirmed by the presence of four telomeric 45S rDNA signals in both male and female plants. All four 45S rDNA sites are rich in heterochromatin evident from the co-localization of telomeric chromomycin A (CMA)(+ve) signals. The size of 45S rDNA signal was found to differ between the homologues of one nucleolar chromosome pair. The distribution of heterochromatin is found to differ among the male and female populations. The average GC-rich heterochromatin content of male and female populations is 23.27 and 29.86 %, respectively. Moreover, the male plants have a genome size of 0.92 pg/2C while the female plants have a size of 0.73 pg/2C, reflecting a huge genomic divergence between the genders. The great variation in genome size is owing to the presence of Y chromosome in the male populations, playing a multifaceted role in sexual divergence in C. grandis.
Schoch, Conrad L.; Seifert, Keith A.; Huhndorf, Sabine; Robert, Vincent; Spouge, John L.; Levesque, C. André; Chen, Wen; Bolchacova, Elena; Voigt, Kerstin; Crous, Pedro W.; Miller, Andrew N.; Wingfield, Michael J.; Aime, M. Catherine; An, Kwang-Deuk; Bai, Feng-Yan; Barreto, Robert W.; Begerow, Dominik; Bergeron, Marie-Josée; Blackwell, Meredith; Boekhout, Teun; Bogale, Mesfin; Boonyuen, Nattawut; Burgaz, Ana R.; Buyck, Bart; Cai, Lei; Cai, Qing; Cardinali, G.; Chaverri, Priscila; Coppins, Brian J.; Crespo, Ana; Cubas, Paloma; Cummings, Craig; Damm, Ulrike; de Beer, Z. Wilhelm; de Hoog, G. Sybren; Del-Prado, Ruth; Dentinger, Bryn; Diéguez-Uribeondo, Javier; Divakar, Pradeep K.; Douglas, Brian; Dueñas, Margarita; Duong, Tuan A.; Eberhardt, Ursula; Edwards, Joan E.; Elshahed, Mostafa S.; Fliegerova, Katerina; Furtado, Manohar; García, Miguel A.; Ge, Zai-Wei; Griffith, Gareth W.; Griffiths, K.; Groenewald, Johannes Z.; Groenewald, Marizeth; Grube, Martin; Gryzenhout, Marieka; Guo, Liang-Dong; Hagen, Ferry; Hambleton, Sarah; Hamelin, Richard C.; Hansen, Karen; Harrold, Paul; Heller, Gregory; Herrera, Cesar; Hirayama, Kazuyuki; Hirooka, Yuuri; Ho, Hsiao-Man; Hoffmann, Kerstin; Hofstetter, Valérie; Högnabba, Filip; Hollingsworth, Peter M.; Hong, Seung-Beom; Hosaka, Kentaro; Houbraken, Jos; Hughes, Karen; Huhtinen, Seppo; Hyde, Kevin D.; James, Timothy; Johnson, Eric M.; Johnson, Joan E.; Johnston, Peter R.; Jones, E.B. Gareth; Kelly, Laura J.; Kirk, Paul M.; Knapp, Dániel G.; Kõljalg, Urmas; Kovács, Gábor M.; Kurtzman, Cletus P.; Landvik, Sara; Leavitt, Steven D.; Liggenstoffer, Audra S.; Liimatainen, Kare; Lombard, Lorenzo; Luangsa-ard, J. Jennifer; Lumbsch, H. Thorsten; Maganti, Harinad; Maharachchikumbura, Sajeewa S. N.; Martin, María P.; May, Tom W.; McTaggart, Alistair R.; Methven, Andrew S.; Meyer, Wieland; Moncalvo, Jean-Marc; Mongkolsamrit, Suchada; Nagy, László G.; Nilsson, R. Henrik; Niskanen, Tuula; Nyilasi, Ildikó; Okada, Gen; Okane, Izumi; Olariaga, Ibai; Otte, Jürgen; Papp, Tamás; Park, Duckchul; Petkovits, Tamás; Pino-Bodas, Raquel; Quaedvlieg, William; Raja, Huzefa A.; Redecker, Dirk; Rintoul, Tara L.; Ruibal, Constantino; Sarmiento-Ramírez, Jullie M.; Schmitt, Imke; Schüßler, Arthur; Shearer, Carol; Sotome, Kozue; Stefani, Franck O.P.; Stenroos, Soili; Stielow, Benjamin; Stockinger, Herbert; Suetrong, Satinee; Suh, Sung-Oui; Sung, Gi-Ho; Suzuki, Motofumi; Tanaka, Kazuaki; Tedersoo, Leho; Telleria, M. Teresa; Tretter, Eric; Untereiner, Wendy A.; Urbina, Hector; Vágvölgyi, Csaba; Vialle, Agathe; Vu, Thuy Duong; Walther, Grit; Wang, Qi-Ming; Wang, Yan; Weir, Bevan S.; Weiß, Michael; White, Merlin M.; Xu, Jianping; Yahr, Rebecca; Yang, Zhu L.; Yurkov, Andrey; Zamora, Juan-Carlos; Zhang, Ning; Zhuang, Wen-Ying; Schindel, David
Six DNA regions were evaluated as potential DNA barcodes for Fungi, the second largest kingdom of eukaryotic life, by a multinational, multilaboratory consortium. The region of the mitochondrial cytochrome c oxidase subunit 1 used as the animal barcode was excluded as a potential marker, because it is difficult to amplify in fungi, often includes large introns, and can be insufficiently variable. Three subunits from the nuclear ribosomal RNA cistron were compared together with regions of three representative protein-coding genes (largest subunit of RNA polymerase II, second largest subunit of RNA polymerase II, and minichromosome maintenance protein). Although the protein-coding gene regions often had a higher percent of correct identification compared with ribosomal markers, low PCR amplification and sequencing success eliminated them as candidates for a universal fungal barcode. Among the regions of the ribosomal cistron, the internal transcribed spacer (ITS) region has the highest probability of successful identification for the broadest range of fungi, with the most clearly defined barcode gap between inter- and intraspecific variation. The nuclear ribosomal large subunit, a popular phylogenetic marker in certain groups, had superior species resolution in some taxonomic groups, such as the early diverging lineages and the ascomycete yeasts, but was otherwise slightly inferior to the ITS. The nuclear ribosomal small subunit has poor species-level resolution in fungi. ITS will be formally proposed for adoption as the primary fungal barcode marker to the Consortium for the Barcode of Life, with the possibility that supplementary barcodes may be developed for particular narrowly circumscribed taxonomic groups. PMID:22454494
Xu, Jiajie; Jiang, Bo; Chai, Sanming; He, Yuan; Zhu, Jianyi; Shen, Zonggen; Shen, Songdong
Filamentous Bangia, which are distributed extensively throughout the world, have simple and similar morphological characteristics. Scientists can classify these organisms using molecular markers in combination with morphology. We successfully sequenced the complete nuclear ribosomal DNA, approximately 13 kb in length, from a marine Bangia population. We further analyzed the small subunit ribosomal DNA gene (nrSSU) and the internal transcribed spacer (ITS) sequence regions along with nine other marine, and two freshwater Bangia samples from China. Pairwise distances of the nrSSU and 5.8S ribosomal DNA gene sequences show the marine samples grouping together with low divergences (00.003; 0-0.006, respectively) from each other, but high divergences (0.123-0.126; 0.198, respectively) from freshwater samples. An exception is the marine sample collected from Weihai, which shows high divergence from both other marine samples (0.063-0.065; 0.129, respectively) and the freshwater samples (0.097; 0.120, respectively). A maximum likelihood phylogenetic tree based on a combined SSU-ITS dataset with maximum likelihood method shows the samples divided into three clades, with the two marine sample clades containing Bangia spp. from North America, Europe, Asia, and Australia; and one freshwater clade, containing Bangia atropurpurea from North America and China.
Ruíz-Estévez, Mercedes; López-León, M Dolores; Cabrero, Josefa; Camacho, Juan Pedro M
B chromosomes are considered to be genetically inert elements. However, some of them are able to show nucleolus organizer region (NOR) activity, as detected by both cytological and molecular means. The grasshopper Eyprepocnemis plorans shows a B chromosome polymorphism characterized by the existence of many B variants. One of them, B24, shows NOR activity in about half of B-carrying males in the Torrox population. Molecular data have suggested the recent origin for B chromosomes in this species, and on this basis it would be expected that NOR activity was widespread among the different B variants. Here we test this hypothesis in four different B chromosome variants (B1, B2, B5, and B24) from 11 natural populations of the grasshopper E. plorans covering the south and east of the Iberian Peninsula plus the Balearic Islands. We used two different approaches: (1) the cytological observation of nucleoli attached to the distal region of the B chromosome (where the rDNA is located), and (2) the molecular detection of the rDNA transcripts carrying an adenine insertion characteristic of B chromosome ITS2 sequences. The results showed NOR expression not only for B24 but also for the B1 and B2 variants. However, the level of B-NOR expression in these latter variants, measured by the proportion of cells showing nucleoli attached to the B chromosomes, was much lower than that previously reported for B24. This suggests the possibility that structural or genetic background conditions are enhancing the expressivity of the rDNA in the B24 variant.
Matejusová, I; Gelnar, M; Verneau, O; Cunningham, C O; Littlewood, D T J
Analyses of small subunit ribosomal RNA gene sequences of representatives of major taxa of Monopisthocotylea were performed to identify the sister group of Gyrodactylus. Nuclear ribosomal DNA sequences from the complete internal transcribed spacer (ITS) region were used to infer phylogeny of 37 Gyrodactylus species and Gyrodactyloides bychowskii, Macrogyrodactylus polypteri and Gyrdicotylus gallieni, using maximum likelihood, parsimony and Bayesian inference. The genus Gyrodactylus appeared to be a monophyletic group in all analyses, based on the present data set. Within the genus, there were 3 major groups recognized by high bootstrap values and posterior probabilities. None of the 6 subgenera appeared to be monophyletic, and the most basal subgenus G. (Gyrodactylus) was paraphyletic. Characteristics of the excretory system of Gyrodactylus do not seem to be conservative enough to reveal subgenera within Gyrodactylus and we suggest abandoning existing subgenera as indicators of phylogeny. The grouping of species based on the morphology of the ventral bar and marginal hooks seems to have sufficient power to infer relationships between the Gyrodactylus species.
vd Schulenburg, J H; Englisch, U; Wägele, J W
A comparison of ribosomal internal transcribed spacer 1 (ITS1) elements of digenetic trematodes (Platyhelminthes) including unidentified digeneans isolated from Cyathura carinata (Crustacea: Isopoda) revealed DNA sequence similarities at more than half of the spacer at its 3' end. Primary sequence similarity was shown to be associated with secondary structure conservation, which suggested that similarity is due to identity by descent and not chance. Using an analysis of apomorphies, the sequence data were shown to produce a distinct phylogenetic signal. This was confirmed by the consistency of results of different tree reconstruction methods such as distance approaches, maximum parsimony, and maximum likelihood. Morphological evidence additionally supported the phylogenetic tree based on ITS1 data and the inferred phylogenetic position of the unidentified digeneans of C. carinata met the expectations from known trematode life-cycle patterns. Although ribosomal ITS1 elements are generally believed to be too variable for phylogenetic analysis above the species or genus level, the overall consistency of the results of this study strongly suggests that this is not the case in digenetic trematodes. Here, 3' end ITS1 sequence data seem to provide a valuable tool for elucidating phylogenetic relationships of a broad range of phylogenetically distinct taxa.
Campbell, Christopher S; Wright, Wesley A; Cox, Margaret; Vining, Thomas F; Major, C Smoot; Arsenault, Matthew P
The nrDNA ITS1 of Picea is 2747-3271 bp, the longest known of all plants. We obtained 24 cloned ITS1 sequences from six individuals of Picea glehnii, Picea mariana, Picea orientalis, and Picea rubens. Mean sequence divergence within these individuals (0.018+/-0.009) is more than half that between the species (0.031+/-0.011) and may be maintained against concerted evolution by separation of Picea 18S-26S rDNA repeats on multiple chromosomes. Picea ITS1 contains three subrepeats with a motif (5'-GGCCACCCTAGTC) that is conserved across Pinaceae. Two subrepeats are tandem, remote from the third, and more closely related and significantly more similar to one another than either is to the third subrepeat. This correlation between similarity and proximity may be the result of subrepeat duplication or concerted evolution within rDNA repeats. In inferred secondary structures, subrepeats generally form long hairpins, with a portion of the Pinaceae conserved motif in the terminal loop, and tandem subrepeats pair with one another over most of their length. Coalescence of ITS1 sequences occurs in P. orientalis but not in the other species.
Larentis, Michael; Alfreider, Albin
A comparison of ribosomal RNA sequence analysis methods based on clone libraries and single-strand conformational polymorphism technique (SSCP) was performed with groundwater samples obtained between 523-555 meters below surface. The coverage of analyzed clones by phylotype-richness estimates was between 88-100%, confirming that the clone libraries were adequately examined. Analysis of individual bands retrieved from SSCP gels identified 1-6 different taxonomic units per band, suggesting that a single SSCP band does often represent more than one single prokaryotic species. The prokaryotic diversity obtained by both methods showed an overall difference of 42-80%. In comparison to SSCP, clone libraries underestimated the phylogenetic diversity and only 36-66% of the phylotypes observed with SSCP were also detected with the clone libraries. An exception was a sample where the SSCP analysis of Archaea identified only half of the phylotypes retrieved by the clone library. Overall, this study suggests that the clone library and the SSCP approach do not provide an identical picture of the prokaryotic diversity in groundwater samples. The results clearly show that the SSCP method, although this approach is prone to generate methodological artifacts, was able to detect significantly more phylotypes than microbial community analysis based on clone libraries.
Zhang, Lijuan; Li, Hu; Li, Shujuan; Zhang, Aibing; Kou, Fei; Xun, Huaizhu; Wang, Pei; Wang, Ying; Song, Fan; Cui, Jianxin; Cui, Jinjie; Gouge, Dawn H.; Cai, Wanzhi
Phylogeographic patterns of some extant plant and vertebrate species have been well studied; however, they are poorly understood in the majority of insects. The study documents analysis of mitochondrial (COI, CYTB and ND5) and nuclear (5.8S rDNA, ITS2 and 28S rDNA) data from 419 individuals of Adelphocoris suturalis, which is one of the main cotton pests found in the 31 locations in China and Japan involved in the study. Results show that the species is highly differentiated between populations from central China and peripheral China regions. Analysis of molecular variance showed a high level of geographical differentiation at different hierarchical levels. Isolation-by-distance test showed no significant correlation between genetic distance and geographical distance among A. suturalis populations, which suggested gene flow is not restricted by distance. In seven peripheral populations, the high levels of genetic differentiation and the small Nem values implied that geographic barriers were more likely restrict gene flow. Neutrality tests and the Bayesian skyline plot suggested population expansion likely happened during the cooling transition between Last Interglacial and Last Glacial Maximum. All lines of evidence suggest that physical barriers, Pleistocene climatic oscillations and geographical heterogeneity have affected the population structure and distribution of this insect in China. PMID:26388034
Gebhardt, Katharina; Knebelsberger, Thomas
We morphologically analyzed 79 cephalopod specimens from the North and Baltic Seas belonging to 13 separate species. Another 29 specimens showed morphological features of either Alloteuthis mediaor Alloteuthis subulata or were found to be in between. Reliable identification features to distinguish between A. media and A. subulata are currently not available. The analysis of the DNA barcoding region of the COI gene revealed intraspecific distances (uncorrected p) ranging from 0 to 2.13 % (average 0.1 %) and interspecific distances between 3.31 and 22 % (average 15.52 %). All species formed monophyletic clusters in a neighbor-joining analysis and were supported by bootstrap values of ≥99 %. All COI haplotypes belonging to the 29 Alloteuthis specimens were grouped in one cluster. Neither COI nor 18S rDNA sequences helped to distinguish between the different Alloteuthis morphotypes. For species identification purposes, we recommend the use of COI, as it showed higher bootstrap support of species clusters and less amplification and sequencing failure compared to 18S. Our data strongly support the assumption that the genus Alloteuthis is only represented by a single species, at least in the North Sea. It remained unclear whether this species is A. subulata or A. media. All COI sequences including important metadata were uploaded to the Barcode of Life Data Systems and can be used as reference library for the molecular identification of more than 50 % of the cephalopod fauna known from the North and Baltic Seas.
Mikaeili, F; Kia, E B; Sharbatkhori, M; Sharifdini, M; Jalalizand, N; Heidari, Z; Zarei, Z; Stensvold, C R; Mirhendi, H
Six simple methods for extraction of ribosomal and mitochondrial DNA from Toxocara canis, Toxocara cati and Toxascaris leonina were compared by evaluating the presence, appearance and intensity of PCR products visualized on agarose gels and amplified from DNA extracted by each of the methods. For each species, two isolates were obtained from the intestines of their respective hosts: T. canis and T. leonina from dogs, and T. cati from cats. For all isolates, total DNA was extracted using six different methods, including grinding, boiling, crushing, beating, freeze-thawing and the use of a commercial kit. To evaluate the efficacy of each method, the internal transcribed spacer (ITS) region and the cytochrome c oxidase subunit 1 (cox1) gene were chosen as representative markers for ribosomal and mitochondrial DNA, respectively. Among the six DNA extraction methods, the beating method was the most cost effective for all three species, followed by the commercial kit. Both methods produced high intensity bands on agarose gels and were characterized by no or minimal smear formation, depending on gene target; however, beating was less expensive. We therefore recommend the beating method for studies where costs need to be kept at low levels.
Bangyeekhun, E; Ryynänen, H J; Henttonen, P; Huner, J V; Cerenius, L; Söderhäll, K
Two morphotypes of the crayfish parasite Psorospermium haeckeli were isolated from 2 crayfish species of different geographical origin. The oval-shaped sporocysts were obtained from the epidermal and connective tissue beneath the carapace of the noble crayfish Astacus astacus from Sweden and Finland. Elongated spores were isolated from the abdominal muscle tissue of the red swamp crayfish Procambarus clarkii from USA. To compare genetic divergence of 2 morphotypes of the parasite, the ribosomal internal transcribed spacer (ITS) DNA (ITS 1 and ITS 2) and the 5.8S rRNA gene were cloned and sequenced. The analysed region is variable in length, with the ribosomal ITS sequence of the European morphotype longer than the North American one. Sequence diversity is found mainly in ITS 1 and ITS 2 regions, and there is 66% and 58% similarity between the 2 morphotypes, respectively. Thus, analysis of the ribosomal ITS DNA suggests that P. haeckeli forms obtained from Europe and North America are genetically diverse, which supports the previously reported morphological characteristics.
Schroeder, Jill M.; Booton, Gregory C.; Hay, John; Niszl, Ingrid A.; Seal, David V.; Markus, Miles B.; Fuerst, Paul A.; Byers, Thomas J.
This study identified subgenic PCR amplimers from 18S rDNA that were (i) highly specific for the genus Acanthamoeba, (ii) obtainable from all known genotypes, and (iii) useful for identification of individual genotypes. A 423- to 551-bp Acanthamoeba-specific amplimer ASA.S1 obtained with primers JDP1 and JDP2 was the most reliable for purposes i and ii. A variable region within this amplimer also identified genotype clusters, but purpose iii was best achieved with sequencing of the genotype-specific amplimer GTSA.B1. Because this amplimer could be obtained from any eukaryote, axenic Acanthamoeba cultures were required for its study. GTSA.B1, produced with primers CRN5 and 1137, extended between reference bp 1 and 1475. Genotypic identification relied on three segments: bp 178 to 355, 705 to 926, and 1175 to 1379. ASA.S1 was obtained from single amoeba, from cultures of all known 18S rDNA genotypes, and from corneal scrapings of Scottish patients with suspected Acanthamoeba keratitis (AK). The AK PCR findings were consistent with culture results for 11 of 15 culture-positive specimens and detected Acanthamoeba in one of nine culture-negative specimens. ASA.S1 sequences were examined for 6 of the 11 culture-positive isolates and were most closely associated with genotypic cluster T3-T4-T11. A similar distance analysis using GTSA.B1 sequences identified nine South African AK-associated isolates as genotype T4 and three isolates from sewage sludge as genotype T5. Our results demonstrate the usefulness of 18S ribosomal DNA PCR amplimers ASA.S1 and GTSA.B1 for Acanthamoeba-specific detection and reliable genotyping, respectively, and provide further evidence that T4 is the predominant genotype in AK. PMID:11326011
Schroeder, J M; Booton, G C; Hay, J; Niszl, I A; Seal, D V; Markus, M B; Fuerst, P A; Byers, T J
This study identified subgenic PCR amplimers from 18S rDNA that were (i) highly specific for the genus Acanthamoeba, (ii) obtainable from all known genotypes, and (iii) useful for identification of individual genotypes. A 423- to 551-bp Acanthamoeba-specific amplimer ASA.S1 obtained with primers JDP1 and JDP2 was the most reliable for purposes i and ii. A variable region within this amplimer also identified genotype clusters, but purpose iii was best achieved with sequencing of the genotype-specific amplimer GTSA.B1. Because this amplimer could be obtained from any eukaryote, axenic Acanthamoeba cultures were required for its study. GTSA.B1, produced with primers CRN5 and 1137, extended between reference bp 1 and 1475. Genotypic identification relied on three segments: bp 178 to 355, 705 to 926, and 1175 to 1379. ASA.S1 was obtained from single amoeba, from cultures of all known 18S rDNA genotypes, and from corneal scrapings of Scottish patients with suspected Acanthamoeba keratitis (AK). The AK PCR findings were consistent with culture results for 11 of 15 culture-positive specimens and detected Acanthamoeba in one of nine culture-negative specimens. ASA.S1 sequences were examined for 6 of the 11 culture-positive isolates and were most closely associated with genotypic cluster T3-T4-T11. A similar distance analysis using GTSA.B1 sequences identified nine South African AK-associated isolates as genotype T4 and three isolates from sewage sludge as genotype T5. Our results demonstrate the usefulness of 18S ribosomal DNA PCR amplimers ASA.S1 and GTSA.B1 for Acanthamoeba-specific detection and reliable genotyping, respectively, and provide further evidence that T4 is the predominant genotype in AK.
Baum, Bernard R; Johnson, Douglas A
A new genus Douglasdeweya containing the two species, Douglasdeweya deweyi and D. wangii was published in 2005 by Yen et al. based upon the results of cytogenetical and morphological findings. The genome constitution of Douglasdeweya-PPStSt-allowed its segregation from the genus Pseudoroegneria which contains the StSt or StStStSt genomes. Our previous work had demonstrated the utility of using 5S rDNA units, especially the non-transcribed spacer sequence variation, for the resolution of genomes (haplomes) previously established by cytology. Here, we show that sequence analysis of the 5S DNA units from these species strongly supports the proposed species relationships of Yen et al. (Can J Bot 83:413-419, 2005), i.e., the PP genome from Agropyron and the StSt genome from Pseudoroegneria. Analysis of the 5S rDNA units constitutes a powerful tool for genomic research especially in the Triticeae.
Moin-Vaziri, Vahideh; Oshaghi, Mohammad Ali; Yaghoobi-Ershadi, Mohammad Reza; Derakhshandeh-Peykar, Pupak; Abaei, Mohammad Reza; Mohtarami, Fatemeh; Zahraei-Ramezani, Ali Reza; Nadim, Aboulhassan
Background: Phlebotomus sergenti s.l. is considered the most likely vector of Leishmania tropica in Iran. Although two morphotypes- P. sergenti sergenti (A) and P. sergenti similis (B)-have been formally described, further morphological and a molecular analysis of mitochondrial cytochrome oxidase I (mtDNA-COI) gene revealed inconsistencies and suggests that the variation between the morphotypes is intraspecific and the morphotypes might be identical species. Methods: We examined the sequence of the ITS2-rDNA of Iranian specimens of P. sergenti s.l., comprising P. cf sergenti, P. cf similis, and intermediate morphotypes, together with available data in Genbank. Results: Sequence analysis showed 5.2% variation among P. sergenti s.l. morphotypes. Almost half of the variation was due to the number of an AT microsatellite repeats in the center of the spacer. Nine haplotypes were found in the species constructing three main lineages corresponding to the origin of the colonies located in southwest (SW), northeast (NE), and northwest-center-southeast (NCS). Lineages NCS and NE included both typical P. cf sergenti and P. cf similis and intermediate morphotypes. Conclusion: Phylogenetic sequence analysis revealed that, except for one Iranian sample, which was close to the European samples, other Iranian haplotypes were associated with the northeastern Mediterranean populations including Turkey, Cyprus, Syria, and Pakistan. Similar to the sequences of mtDNA COI gene, ITS2 sequences could not resolve P. sergenti from P. similis and did not support the possible existence of sibling species or subspecies within P. sergenti s.l.. PMID:28032098
Cepeda, Georgina D.; Blanco-Bercial, Leocadio; Bucklin, Ann; Berón, Corina M.; Viñas, María D.
Species of Oithona (Copepoda, Cyclopoida) are highly abundant, ecologically important, and widely distributed throughout the world oceans. Although there are valid and detailed descriptions of the species, routine species identifications remain challenging due to their small size, subtle morphological diagnostic traits, and the description of geographic forms or varieties. This study examined three species of Oithona (O. similis, O. atlantica and O. nana) occurring in the Argentine sector of the South Atlantic Ocean based on DNA sequence variation of a 575 base-pair region of 28S rDNA, with comparative analysis of these species from other North and South Atlantic regions. DNA sequence variation clearly resolved and discriminated the species, and revealed low levels of intraspecific variation among North and South Atlantic populations of each species. The 28S rDNA region was thus shown to provide an accurate and reliable means of identifying the species throughout the sampled domain. Analysis of 28S rDNA variation for additional species collected throughout the global ocean will be useful to accurately characterize biogeographical distributions of the species and to examine phylogenetic relationships among them. PMID:22558245
Cepeda, Georgina D; Blanco-Bercial, Leocadio; Bucklin, Ann; Berón, Corina M; Viñas, María D
Species of Oithona (Copepoda, Cyclopoida) are highly abundant, ecologically important, and widely distributed throughout the world oceans. Although there are valid and detailed descriptions of the species, routine species identifications remain challenging due to their small size, subtle morphological diagnostic traits, and the description of geographic forms or varieties. This study examined three species of Oithona (O. similis, O. atlantica and O. nana) occurring in the Argentine sector of the South Atlantic Ocean based on DNA sequence variation of a 575 base-pair region of 28S rDNA, with comparative analysis of these species from other North and South Atlantic regions. DNA sequence variation clearly resolved and discriminated the species, and revealed low levels of intraspecific variation among North and South Atlantic populations of each species. The 28S rDNA region was thus shown to provide an accurate and reliable means of identifying the species throughout the sampled domain. Analysis of 28S rDNA variation for additional species collected throughout the global ocean will be useful to accurately characterize biogeographical distributions of the species and to examine phylogenetic relationships among them.
Edgcomb, Virginia P.; McDonald, John H.; Devereux, Richard; Smith, David W.
The feasibility of using probes directed towards ribosomal DNAs (rDNAs) as a quantitative approach to estimating cell numbers was examined and applied to study the structure of a bacterial community in humic acid-rich salt marsh sediments. Hybridizations were performed with membrane-bound nucleic acids by using seven group-specific DNA oligonucleotide probes complementary to 16S rRNA coding regions. These included a general eubacterial probe and probes encompassing most members of the gram-negative, mesophilic sulfate-reducing bacteria (SRB). DNA was extracted from sediment samples, and contaminating materials were removed by a series of steps. Efficiency of DNA extraction was 48% based on the recovery of tritiated plasmid DNA added to samples prior to extraction. Reproducibility of the extraction procedure was demonstrated by hybridizations to replicate samples. Numbers of target cells in samples were estimated by comparing the amount of hybridization to extracted DNA obtained with each probe to that obtained with a standard curve of genomic DNA for reference strains included on the same membrane. In June, numbers of SRB detected with an SRB-specific probe ranged from 6.0 × 107 to 2.5 × 109 (average, 1.1 × 109 ± 5.2 × 108) cells g of sediment−1. In September, numbers of SRB detected ranged from 5.4 × 108 to 7.3 × 109 (average, 2.5 × 109 ± 1.5 × 109) cells g of sediment−1. The capability of using rDNA probes to estimate cell numbers by hybridization to DNA extracted from complex matrices permits initiation of detailed studies on community composition and changes in communities based on cell numbers in formerly intractable environments. PMID:10103245
Lyckegaard, E M; Clark, A G
Multigene families on the Y chromosome face an unusual array of evolutionary forces. Both ribosomal DNA and Stellate, the two families examined here, have multiple copies of similar sequences on the X and Y chromosomes. Although the rate of sequence divergence on the Y chromosome depends on rates of mutation, gene conversion and exchange with the X chromosome, as well as purifying selection, the regulation of gene copy number may also depend on other pleiotropic functions, such as maintenance of chromosome pairing. Gene copy numbers were estimated for a series of 34 Y chromosome replacement lines using densitometric measurements of slot blots of genomic DNA from adult Drosophila melanogaster. Scans of autoradiographs of the same blots probed with the cloned alcohol dehydrogenase gene, a single copy gene, served as internal standards. Copy numbers span a 6-fold range for ribosomal DNA and a 3-fold range for Stellate DNA. Despite this magnitude of variation, there was no association between copy number and segregation variation of the sex chromosomes.
However, in Allopb,/er, there are examples of rONA intragenomic variation (\\X’ilkerson et al. 2004; Fairley et al. 2005), but its prevalence and...Anopheles species (Onyabe and Conn 1999; Wilkerson et al. 2004; Fairley et aI. 200S) and in other mos- quitoes in subfamily Culicinae (Black et a!. 1989...DNA 1TS2 sequences. J :-.led Entomo!’ 33:109-116. Dover GA. 1982. Molecular dri"e: a cnhesive mode of species evolution. Nature. 299:111-117. Fairley
Wolcott, Randall D; Hanson, John D; Rees, Eric J; Koenig, Lawrence D; Phillips, Caleb D; Wolcott, Richard A; Cox, Stephen B; White, Jennifer S
The extent to which microorganisms impair wound healing is an ongoing controversy in the management of chronic wounds. Because the high diversity and extreme variability of the microbiota between individual chronic wounds lead to inconsistent findings in small cohort studies, evaluation of a large number of chronic wounds using identical sequencing and bioinformatics methods is necessary for clinicians to be able to select appropriate empiric therapies. In this study, we utilized 16S rDNA pyrosequencing to analyze the composition of the bacterial communities present in samples obtained from patients with chronic diabetic foot ulcers (N = 910), venous leg ulcers (N = 916), decubitus ulcers (N = 767), and nonhealing surgical wounds (N = 370). The wound samples contained a high proportion of Staphylococcus and Pseudomonas species in 63 and 25% of all wounds, respectively; however, a high prevalence of anaerobic bacteria and bacteria traditionally considered commensalistic was also observed. Our results suggest that neither patient demographics nor wound type influenced the bacterial composition of the chronic wound microbiome. Collectively, these findings indicate that empiric antibiotic selection need not be based on nor altered for wound type. Furthermore, the results provide a much clearer understanding of chronic wound microbiota in general; clinical application of this new knowledge over time may help in its translation to improved wound healing outcomes.
Black, W C; Piesman, J
Ticks are parasitiform mites that are obligate hematophagous ectoparasites of amphibians, reptiles, birds, and mammals. A phylogeny for tick families, subfamilies, and genera has been described based on morphological characters, life histories, and host associations. To test the existing phylogeny, we sequenced approximately 460 bp from the 3' end of the mitochondrial 16S rRNA gene (rDNA) in 36 hard- and soft-tick species; a mesostigmatid mite, Dermanyssus gallinae, was used as an outgroup. Phylogenies derived using distance, maximum-parsimony, or maximum-likelihood methods were congruent. The existing phylogeny was largely supported with four exceptions. In hard ticks (Ixodidae), members of Haemaphysalinae were monophyletic with the primitive Amblyomminae and members of Hyalomminae grouped within the Rhipicephalinae. In soft ticks (Argasidae), the derived phylogeny failed to support a monophyletic relationship among members of Ornithodorinae and supported placement of Argasinae as basal to the Ixodidae, suggesting that hard ticks may have originated from an Argas-like ancestor. Because most Argas species are obligate bird octoparasites, this result supports earlier suggestions that hard ticks did not evolve until the late Cretaceous. PMID:7937832
Wu, Li-Hsin; Hoffmann, Ary A.; Thomson, Linda J.
Egg parasitoids of the genus Trichogramma are natural enemies of many lepidopteran borers in agricultural areas around the world. It is important to identify the correct species and ideally focus on endemic Trichogramma for pest control in particular crops. In this study, Trichogramma wasps were collected from parasitized eggs of Asian corn borer in Southwestern Taiwan. Three Trichogramma species, Trichogramma ostriniae Pang and Chen, Trichogramma chilonis Ishii, and T. sp. y, were identified based on morphology and the nucleotide sequence of the internal transcribed spacer 2 (ITS-2) region of rDNA. Although T. ostriniae and T. sp. y appear to be morphologically similar, ITS-2 identity between these two taxa is only 89%. Surprisingly, a commercially released Trichogramma colony thought to be T. chilonis possessed 99% identity (ITS-2) with the field T. sp. y individuals. This suggests past contamination leading to subsitution of the laboratory-reared T. chilonis colony by T. sp. y. Natural populations of all three Trichogramma species were found to be infected by a single Wolbachia strain which was identified using a wsp gene sequence. PMID:26896674
Dupont, Jöelle; Dennetière, Bruno; Jacquet, Claire; Dupont, Marie France
RFLP of ITS rDNA is proposed as a useful tool for molecular identification of the most common species of biverticillate penicillia. 60 isolates were analysed representing 13 species and 21 unique sequences were produced. The combination of five restriction enzymes was successful in separating 12 species. However, the variety Penicillium purpurogenum var. rubrisclerotium remained indistinguishable from Penicillium funiculosum. P. funiculosum appeared as the most confused species, being mis-identified with Penicillium miniolutum and Penicillium pinophilum, which were originally part of the species, and with P. purpurogenum perhaps because of the common production of red pigment. Penicillium variabile was difficult to investigate as introns were found on half of the isolates. Penicillium piceum, Penicillium rugulosum, Penicillium loliense, Penicillium erythromellis and P. purpurogenum were homogeneous from molecular and morphological positions and corresponded to a well circumscribed taxon. Furthermore, intraspecific variability was evidenced within P. pinophilum and P. funiculosum. The ex-type isolate of P. funiculosum produced a unique pattern. The method is sensitive, rapid and inexpensive and can be used for isolate identification of the biverticillate species. It is recommended particularly when many isolates have to be authentificated prior to analysis for phylogenetic assessment or population genetics.
Ko, Jong Hyun; Choe, Yong Beom; Ahn, Kyu Joong
Background So far, studies on the inter-relationship between Malassezia and Malassezia folliculitis have been rather scarce. Objective We sought to analyze the differences in body sites, gender and age groups, and to determine whether there is a relationship between certain types of Malassezia species and Malassezia folliculitis. Methods Specimens were taken from the forehead, cheek and chest of 60 patients with Malassezia folliculitis and from the normal skin of 60 age- and gender-matched healthy controls by 26S rDNA PCR-RFLP. Results M. restricta was dominant in the patients with Malassezia folliculitis (20.6%), while M. globosa was the most common species (26.7%) in the controls. The rate of identification was the highest in the teens for the patient group, whereas it was the highest in the thirties for the control group. M. globosa was the most predominant species on the chest with 13 cases (21.7%), and M. restricta was the most commonly identified species, with 17 (28.3%) and 12 (20%) cases on the forehead and cheek, respectively, for the patient group. Conclusion Statistically significant differences were observed between the patient and control groups for the people in their teens and twenties, and in terms of the body site, on the forehead only. PMID:21747616
Reeder, T W
The phylogenetic relationships among 40 species, representing all genera, within the North American lizard family Phrynosomatidae were inferred from mitochondrial ribosomal RNA gene sequences. Cladistic analysis of the DNA sequence data (779 bp; 162 informative characters) supported the monophyly of the sand lizards (Callisaurus, Cophosaurus, Holbrookia, and Uma), Petrosaurus, Phrynosoma, Urosaurus, and Uta. All the species of Sceloporus, except S. variabilis and S. chrysostictus, formed a clade. Except for a sand lizard + Phrynosoma clade, the intergeneric relationships inferred from the mtDNA were largely incongruent with recent cladistic analyses based on morphology. Sceloporus group monophyly was not supported, with Petrosaurus being a member of a clade containing Sator, Sceloporus, and Urosaurus, to the exclusion of Uta. The phylogenetic placement of Uta was ambiguous. The substitutional bias in the phrynosomatid mitochondrial rDNA sequences was examined, as well as the phylogenetic information content of transitions relative to transversions. There appeared to be a lower transition bias than observed in other vertebrate sequences, with some classes of transversions occurring as frequently as G <-> A transitions. Transitions were no less informative for phylogeny reconstruction than transversions. Therefore, transitions should not be down-weighted in phylogenetic analysis, as is often done.
Kowalchuk, G A; Gerards, S; Woldendorp, J W
Marram grass (Ammophila arenaria L.), a sand-stabilizing plant species in coastal dune areas, is affected by a specific pathosystem thought to include both plant-pathogenic fungi and nematodes. To study the fungal component of this pathosystem, we developed a method for the cultivation-independent detection and characterization of fungi infecting plant roots based on denaturing gradient gel electrophoresis (DGGE) of specifically amplified DNA fragments coding for 18S rRNA (rDNA). A nested PCR strategy was employed to amplify a 569-bp region of the 18S rRNA gene, with the addition of a 36-bp GC clamp, from fungal isolates, from roots of test plants infected in the laboratory, and from field samples of marram grass roots from both healthy and degenerating stands from coastal dunes in The Netherlands. PCR products from fungal isolates were subjected to DGGE to examine the variation seen both between different fungal taxa and within a single species. DGGE of the 18S rDNA fragments could resolve species differences from fungi used in this study yet was unable to discriminate between strains of a single species. The 18S rRNA genes from 20 isolates of fungal species previously recovered from A. arenaria roots were cloned and partially sequenced to aid in the interpretation of DGGE data. DGGE patterns recovered from laboratory plants showed that this technique could reliably identify known plant-infecting fungi. Amplification products from field A. arenaria roots also were analyzed by DGGE, and the major bands were excised, reamplified, sequenced, and subjected to phylogenetic analysis. Some recovered 18S rDNA sequences allowed for phylogenetic placement to the genus level, whereas other sequences were not closely related to known fungal 18S rDNA sequences. The molecular data presented here reveal fungal diversity not detected in previous culture-based surveys. PMID:9327549
"Mutations" in the pattern of CpG methylation imprinting of the human genome have been correlated with a number of diseases including cancer. In particular, aberrant imprinting of tumor suppressor genes by gain of CpG methylation has been observed in many cancers and thus represents an important alternative pathway to gene "mutation" and tumor progression. Inhibitors of DNA methylation display therapeutic effects in the treatment of certain cancers, and it has been assumed these effects are due to the reversal of "mutant" gene imprinting. However, significant reactivation of imprinted tumor suppressor genes is rarely observed in vivo following treatment with DNA methylation inhibitors. A recent study revealed an unexpected requirement for CpG methylation in the synthesis and assembly of the ribosome, an essential function for cell growth and proliferation. As such, the data provide an unforeseen explanation of the action of DNA methylation inhibitors in restricting cancer cell growth.
Varela, Eduardo S; Lima, João P M S; Galdino, Alexsandro S; Pinto, Luciano da S; Bezerra, Walderly M; Nunes, Edson P; Alves, Maria A O; Grangeiro, Thalles B
The complete sequences of nuclear ribosomal DNA (nrDNA) internal transcribed spacer regions (ITS/5.8S) were determined for species belonging to six genera from the subtribe Diocleinae as well as for the anomalous genera Calopogonium and Pachyrhizus. Phylogenetic trees constructed by distance matrix, maximum parsimony and maximum likelihood methods showed that Calopogonium and Pachyrhizus were outside the clade Diocleinae (Canavalia, Camptosema, Cratylia, Dioclea, Cymbosema, and Galactia). This finding supports previous morphological, phytochemical, and molecular evidence that Calopogonium and Pachyrhizus do not belong to the subtribe Diocleinae. Within the true Diocleinae clade, the clustering of genera and species were congruent with morphology-based classifications, suggesting that ITS/5.8S sequences can provide enough informative sites to allow resolution below the genus level. This is the first evidence of the phylogeny of subtribe Diocleinae based on nuclear DNA sequences.
Diagnostic accuracy of a 16S ribosomal DNA gene-based molecular technique (RT-PCR, microarray, and sequencing) for bacterial meningitis, early-onset neonatal sepsis, and spontaneous bacterial peritonitis.
Esparcia, Oscar; Montemayor, Michel; Ginovart, Gemma; Pomar, Virginia; Soriano, Germán; Pericas, Roser; Gurgui, Mercedes; Sulleiro, Elena; Prats, Guillem; Navarro, Ferran; Coll, Pere
The diagnostic accuracy of a 16S ribosomal DNA (rDNA) gene-based molecular technique for bacterial meningitis (BM), early-onset neonatal sepsis (EONS), and spontaneous bacterial peritonitis (SBP) is evaluated. The molecular approach gave better results for BM diagnosis: sensitivity (S) was 90.6% compared to 78.1% for the bacterial culture. Percentages of cases correctly diagnosed (CCD) were 91.7% and 80.6%, respectively. For EONS diagnosis, S was 60.0% for the molecular approach and 70.0% for the bacterial culture; and CCD was 95.2% and 96.4%, respectively. For SPB diagnosis, the molecular approach gave notably poorer results than the bacterial cultures. S and CCD were 48.4% and 56.4% for the molecular approach and 80.6% and 89.1% for bacterial cultures. Nevertheless, bacterial DNA was detected in 53.3% of culture-negative samples. Accuracy of the 16S rDNA PCR approach differs depending on the sample, the microorganisms involved, the expected bacterial load, and the presence of bacterial DNA other than that from the pathogen implied in the infectious disease.
Porter, Teresita M; Skillman, Jane E; Moncalvo, Jean-Marc
This is the first study to assess the diversity and community structure of the Agaricomycotina in an ectotrophic forest using above-ground fruiting body surveys as well as soil rDNA sampling. We recovered 132 molecular operational taxonomic units, or 'species', from fruiting bodies and 66 from soil, with little overlap. Fruiting body sampling primarily recovered fungi from the Agaricales, Russulales, Boletales and Cantharellales. Many of these species are ectomycorrhizal and form large fruiting bodies. Soil rDNA sampling recovered fungi from these groups in addition to taxa overlooked during the fruiting body survey from the Atheliales, Trechisporales and Sebacinales. Species from these groups form inconspicuous, resupinate and corticioid fruiting bodies. Soil sampling also detected fungi from the Hysterangiales that form fruiting bodies underground. Generally, fruiting body and soil rDNA samples recover a largely different assemblage of fungi at the species level; however, both methods identify the same dominant fungi at the genus-order level and ectomycorrhizal fungi as the prevailing type. Richness, abundance, and phylogenetic diversity (PD) identify the Agaricales as the dominant fungal group above- and below-ground; however, we find that molecularly highly divergent lineages may account for a greater proportion of total diversity using the PD measure compared with richness and abundance. Unless an exhaustive inventory is required, the rapidity and versatility of DNA-based sampling may be sufficient for a first assessment of the dominant taxonomic and ecological groups of fungi in forest soil.
Wang, Jian-Yan; Zhen, Yu; Wang, Guo-shan; Mi, Tie-Zhu; Yu, Zhi-gang
Taking the moon jellyfish Aurelia sp. commonly found in our coastal sea areas as test object, its genome DNA was extracted, the partial sequences of mt-16S rDNA (650 bp) and mt-COI (709 bp) were PCR-amplified, and, after purification, cloning, and sequencing, the sequences obtained were BLASTn-analyzed. The sequences of greater difference with those of the other jellyfish were chosen, and eight specific primers for the mt-16S rDNA and mt-COI of Aurelia sp. were designed, respectively. The specificity test indicated that the primer AS3 for the mt-16S rDNA and the primer AC3 for the mt-COI were excellent in rapidly detecting the target jellyfish from Rhopilema esculentum, Nemopilema nomurai, Cyanea nozakii, Acromitus sp., and Aurelia sp., and thus, the techniques for the molecular identification and detection of moon jellyfish were preliminarily established, which could get rid of the limitations in classical morphological identification of Aurelia sp. , being able to find the Aurelia sp. in the samples more quickly and accurately.
Background The Batrachoididae family is a group of marine teleosts that includes several species with more complicated physiological characteristics, such as their excretory, reproductive, cardiovascular and respiratory systems. Previous studies of the 5S rDNA gene family carried out in four species from the Western Atlantic showed two types of this gene in two species but only one in the other two, under processes of concerted evolution and birth-and-death evolution with purifying selection. Here we present results of the 5S rDNA and another two gene families in Halobatrachus didactylus, an Eastern Atlantic species, and draw evolutionary inferences regarding the gene families. In addition we have also mapped the genes on the chromosomes by two-colour fluorescence in situ hybridization (FISH). Results Two types of 5S rDNA were observed, named type α and type β. Molecular analysis of the 5S rDNA indicates that H. didactylus does not share the non-transcribed spacer (NTS) sequences with four other species of the family; therefore, it must have evolved in isolation. Amplification with the type β specific primers amplified a specific band in 9 specimens of H. didactylus and two of Sparus aurata. Both types showed regulatory regions and a secondary structure which mark them as functional genes. However, the U2 snRNA gene and the ITS-1 sequence showed one electrophoretic band and with one type of sequence. The U2 snRNA sequence was the most variable of the three multigene families studied. Results from two-colour FISH showed no co-localization of the gene coding from three multigene families and provided the first map of the chromosomes of the species. Conclusions A highly significant finding was observed in the analysis of the 5S rDNA, since two such distant species as H. didactylus and Sparus aurata share a 5S rDNA type. This 5S rDNA type has been detected in other species belonging to the Batrachoidiformes and Perciformes orders, but not in the Pleuronectiformes
Meli, Marina L.; Novacco, Marilisa; Borel, Nicole
The 18S ribosomal RNA (rRNA) gene is present in all eukaryotic cells. In this study, we evaluated the use of this gene to verify the presence of PCR-amplifiable host (animal) DNA as an indicator of sufficient sample quality for quantitative real-time PCR (qPCR) analysis. We compared (i) samples from various animal species, tissues, and sample types, including swabs; (ii) multiple DNA extraction methods; and (iii) both fresh and formalin-fixed paraffin-embedded (FFPE) samples. Results showed that 18S ribosomal RNA gene amplification was possible from all tissue samples evaluated, including avian, reptile, and FFPE samples and most swab samples. A single swine rectal swab, which showed sufficient DNA quantity and the demonstrated lack of PCR inhibitors, nonetheless was negative by 18S qPCR. Such a sample specifically illustrates the improvement of determination of sample integrity afforded by inclusion of 18S rRNA gene qPCR analysis in addition to spectrophotometric analysis and the use of internal controls for PCR inhibition. Other possible applications for the described 18S rRNA qPCR are preselection of optimal tissue specimens for studies or preliminary screening of archived samples prior to acceptance for biobanking projects. PMID:27672657
Desquesnes, Marc; Marc, Desquesnes; Kamyingkird, Ketsarin; Ketsarin, Kamyingkird; Yangtara, Sarawut; Sarawut, Yangtara; Milocco, Cristina; Cristina, Milocco; Ravel, Sophie; Sophie, Ravel; Wang, Ming-Hui; Ming-Hui, Wang; Lun, Zhao-Rong; Zhao-Rong, Lun; Morand, Serge; Serge, Morand; Jittapalapong, Sathaporn; Sathaporn, Jittapalapong
Trypanosoma lewisi is a mild or non-pathogenic parasite of the sub-genus Herpetosoma transmitted by fleas to rats. In a previous study we described pan-trypanosome specific primers TRYP1 which amplify the ITS1 of ribosomal DNA by hybridizing in highly conserved regions of 18S and 5.8S genes. These primers proved to be useful for detecting T. lewisi DNA in laboratory rats, but a recent large scale survey in wild rodents demonstrated a lack of specificity. In the present study, we designed and evaluated mono-specific primers LEW1S and LEW1R, for the detection and identification of T. lewisi by a single-step PCR. These primers were designed inside the highly variable region of the ITS1 sequence of T. lewisi ribosomal DNA. The product size of 220 bp is specific to T. lewisi. The sensitivity limit was estimated between 0.055 and 0.55 pg of DNA per reaction, equivalent to 1-10 organisms per reaction. All the PCR products obtained from 6 different T. lewisi isolates were more than 98% similar with each other and similar to the sequences of T. lewisi already published in Genbank. All DNA of 7 T. lewisi stocks from China gave the specific 220 bp product. We showed that LEW1S and LEW1R primers enabled sensitive detection and identification of T. lewisi infection in laboratory and wild rats. This assay is recommended for monitoring T. lewisi infections in rat colonies or for studying infections in the wild fauna. An absence of cross reaction with human DNA means that these primers can be used to investigate atypical trypanosome infections in humans. Given the risk of T. lewisi infection in human, we believe that these primers will be beneficial for public health diagnosis and rodents investigation programmes.
Zhang, Xi; Duan, Jiang Yang; Wang, Zhong Quan; Jiang, Peng; Liu, Ruo Dan; Cui, Jing
Although medically important, the systematics of Spirometra and the taxonomic position of S. erinaceieuropaei remain unclear. In this study, the 18S rDNA gene of S. erinaceieuropaei sparganum from naturally infected frogs caught in 14 geographical locations of China was sequenced. In addition, all available 18S sequences of the family Diphyllobothriidae in the Genbank database were included to reconstruct the phylogeny of diphyllobothriid tapeworms. The secondary structure model of the 18S rDNA was also predicated to further explore the sequence variation. Phylogenetic analyses were performed using maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) methods. The intraspecific divergences of 18S rDNA in Chinese sparganum isolates ranged from 0.0 to 0.4%. Regions of V2, V4 and V7 were the most variable regions in the secondary structure of 18S rDNA. With the exception of genera Duthiersia and Probothriocephalus, other genera (i.e., Adenocephalus, Diphyllobothrium, Diplogonoporus, Duthiersia, Schistocephalus and Spirometra) selected in the Diphyllobothriidae shared similar topologies of V2, V4 and V7 structures. The topology of generated phylogenetic trees revealed close relationships among Adenocephalus, Digramma, Diphyllobothrium, Diplogonoporus, Ligula, Sparganum and Spirometra. The exact phylogenetic position of Spirometra species should be further analyzed with more sampling and more useful molecular markers.
Sajdak, S L; Reed, K M; Phillips, R B
This study was designed to characterize further the nontranscribed intergenic spacers (NTSs) of the 5S rRNA genes of fish and evaluate this marker as a tool for comparative studies. Two members of the closely related North American Great Lakes cisco species complex (Coregonus artedi and C. zenithicus) were chosen for comparison. Fluorescence in situ hybridization found the ciscoes to have a single multicopy 5S locus located in a C band-positive region of the largest submetacentric chromosome. The entire NTS was amplified from the two species by polymerase chain reaction with oligonucleotide primers anchored in the conserved 5S coding region. Complete sequences were determined for 25 clones from four individuals representing two discrete NTS length variants. Sequence analysis found the length variants to result from presence of a 130-bp direct repeat. No two sequences from a single fish were identical. Examination of sequence from the coding region revealed two types of 5S genes in addition to pseudogenes. This suggests the presence of both somatic and germline (oocyte) forms of the 5S gene in the genome of Coregonus. The amount of variation present among NTS sequences indicates that accumulation of variation (mutation) is greater in this multicopy gene than is gene conversion (homogenization). The high level of sequence variation makes the 5S NTS an inappropriate DNA sequence for comparisons of closely related taxa.
Hardin, Dana S
Somatotropin (growth hormone, GH) of recombinant DNA origin has provided a readily available and safe drug that has greatly improved management of children and adolescents with GH deficiency (GHD) and other disorders of growth. In the US and Europe, regulatory agencies have given approval for the use of GH in children and adults who meet specific criteria. However, clinical and ethical controversies remain regarding the diagnosis of GHD, dosing of GH, duration of therapy and expected outcomes. Areas which also require consensus include management of pubertal patients, transitioning pediatric patients to adulthood, management of children with idiopathic short stature and the role of recombinant IGF-1 in treatment. Additionally, studies have demonstrated anabolic benefits of GH in children who have inflammatory-based underlying disease and efficacy of GH in overcoming growth delays in people treated chronically with corticosteroids. These areas are open for possible new uses of this drug. This review summarizes current indications for GH use in children and discusses areas of clinical debate and potential anabolic uses in chronic illness.
Burton, N P; Norris, P R
DNA was extracted from water and sediment samples taken from acidic, geothermal pools on the Caribbean island of Montserrat. 16S rRNA genes were amplified by PCR, cloned, sequenced, and examined to indicate some of the organisms that might be significant components of the in situ microbiota. A clone bank representing the lowest temperature pool that was sampled (33 degrees C) was dominated by genes corresponding to two types of acidophiles: Acidiphilium-like mesophilic heterotrophs and thermotolerant Acidithiobacillus caldus. Three clone types with origins in low- and moderate- (48 degrees C) temperature pools corresponded to bacteria that could be involved in metabolism of sulfur compounds: the aerobic A. caldus and putative anaerobic, moderately thermophilic, sulfur-reducing bacteria (from an undescribed genus and from the Desulfurella group). A higher-temperature sample indicated the presence of a Ferroplasma-like organism, distinct from the other strains of these recently recognized acidophilic, iron-oxidizing members of the Euryarchaeota. Acidophilic Archaea from undescribed genera related to Sulfolobus and Acidianus were predicted to dominate the indigenous acidophilic archaeal population at the highest temperatures.
Villa-Hernández, J M; Dinkova, T D; Aguilar-Caballero, R; Rivera-Cabrera, F; Sánchez de Jiménez, E; Pérez-Flores, L J
Ribosome biogenesis is a pre-requisite for cell growth and proliferation; it is however, a highly regulated process that consumes a great quantity of energy. It requires the coordinated production of rRNA, ribosomal proteins and non-ribosomal factors which participate in the processing and mobilization of the new ribosomes. Ribosome biogenesis has been studied in yeast and animals; however, there is little information about this process in plants. The objective of the present work was to study ribosome biogenesis in maize seeds during germination, a stage characterized for its fast growth, and the effect of insulin in this process. Insulin has been reported to accelerate germination and to induce seedling growth. It was observed that among the first events reactivated just after 3 h of imbibition are the rDNA transcription and the pre-rRNA processing and that insulin stimulates both of them (40-230%). The transcript of nucleolin, a protein which regulates rDNA transcription and pre-rRNA processing, is among the messages stored in quiescent dry seeds and it is mobilized into the polysomal fraction during the first hours of imbibition (6 h). In contrast, de novo ribosomal protein synthesis was low during the first hours of imbibition (3 and 6 h) increasing by 60 times in later stages (24 h). Insulin increased this synthesis (75%) at 24 h of imbibition; however, not all ribosomal proteins were similarly regulated. In this regard, an increase in RPS6 and RPL7 protein levels was observed, whereas RPL3 protein levels did not change even though its transcription was induced. Results show that ribosome biogenesis in the first stages of imbibition is carried out with newly synthesized rRNA and ribosomal proteins translated from stored mRNA.
Escalante, Adelfo; Rodríguez, María Elena; Martínez, Alfredo; López-Munguía, Agustín; Bolívar, Francisco; Gosset, Guillermo
The bacterial diversity in pulque, a traditional Mexican alcoholic fermented beverage, was studied in 16S rDNA clone libraries from three pulque samples. Sequenced clones identified as Lactobacillus acidophilus, Lactobacillus strain ASF360, L. kefir, L. acetotolerans, L. hilgardii, L. plantarum, Leuconostoc pseudomesenteroides, Microbacterium arborescens, Flavobacterium johnsoniae, Acetobacter pomorium, Gluconobacter oxydans, and Hafnia alvei, were detected for the first time in pulque. Identity of 16S rDNA sequenced clones showed that bacterial diversity present among pulque samples is dominated by Lactobacillus species (80.97%). Seventy-eight clones exhibited less than 95% of relatedness to NCBI database sequences, which may indicate the presence of new species in pulque samples.
Liu, Tianyu; Liang, Yinan; Zhong, Xiuqin; Wang, Ning; Hu, Dandan; Zhou, Xuan; Gu, Xiaobin; Peng, Xuerong; Yang, Guangyou
Dirofilaria immitis (heartworm) is the causative agent of an important zoonotic disease that is spread by mosquitoes. In this study, molecular and phylogenetic characterization of D. immitis were performed based on complete ND1 and 16S rDNA gene sequences, which provided the foundation for more advanced molecular diagnosis, prevention, and control of heartworm diseases. The mutation rate and evolutionary divergence in adult heartworm samples from seven dogs in western China were analyzed to obtain information on genetic diversity and variability. Phylogenetic relationships were inferred using both maximum parsimony (MP) and Bayes methods based on the complete gene sequences. The results suggest that D. immitis formed an independent monophyletic group in which the 16S rDNA gene has mutated more rapidly than has ND1. PMID:24639299
Wang, Fei; Zassman, Stefanie; Goldberg, Philip A
Background As the first once-daily basal insulin analog, insulin glargine 100 U/mL (Gla-100; Lantus®) rapidly evolved into the most commonly prescribed insulin therapy worldwide. However, this insulin has clinical limitations. The approval of new basal insulin analogs in 2015 has already started to alter the prescribing landscape. Objective To review the available evidence on the clinical efficacy and safety of a more concentrated insulin glargine (recombinant DNA origin) injection 300 U/mL (Gla-300) compared to insulin Gla-100 in patients with type 1 and type 2 diabetes mellitus (T1DM and T2DM). Methods The following electronic databases were searched: PubMed and MEDLINE (using Ovid platform), Scopus, BIOSIS, and Google Scholar through June 2016. Conference proceedings of the American Diabetes Association (2015–2016) were reviewed. We also manually searched reference lists of pertinent reviews and trials. Results A total of 6 pivotal Phase III randomized controlled trials known as the EDITION series were reviewed. All of these trials (n=3,500) were head-to-head comparisons evaluating the efficacy and tolerability of Gla-300 vs Gla-100 in a diverse population with T1DM and T2DM. These trials were of 6 months duration with a 6-month safety extension phase. Conclusion Gla-300 was as effective as Gla-100 for improving glycemic control over 6 months in all studies, with a lower risk of nocturnal hypoglycemia significant only in insulin-experienced patients with T2DM. Overall, patients on Gla-300 required 10%–18% more basal insulin, but with less weight gain compared with Gla-100. PMID:27980431
Zhao, G H; Jia, Y Q; Bian, Q Q; Nisbet, A J; Cheng, W Y; Liu, Y; Fang, Y Q; Ma, X T; Yu, S K
Internal transcribed spacer (ITS) rDNA sequences of three Nematodirus species from naturally infected goats or sheep in two endemic provinces of China were analysed to establish an effective molecular approach to differentiate Nematodirus species in small ruminants. The respective intra-specific genetic variations in ITS1 and ITS2 rDNA regions were 0.3-1.8% and 0-0.4% in N. spathiger, 0-6.5% and 0-5.4% in N. helvetianus, and 0-4.4% and 0-6.1% in N. oiratianus from China. The respective intra-specific variations of ITS1 and ITS2 were 1.8-4.4% and 1.6-6.1% between N. oiratianus isolates from China and Iran, 5.7-7.1% and 6.3-8.3% between N. helvetianus samples from China and America. For N. spathiger, compared with samples from China, sequence differences in ITS1 rDNA were 0.3-2.4% in isolates from America, 0.3-2.9% in New Zealand and 2.1-2.4% in Australia. Genetic variations in ITS2 rDNA of N. spathiger were 0-0.4% between samples from China and America, and 0-0.8% between samples from China and New Zealand. Using mutation sites, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and specific PCR techniques were developed to differentiate these three Nematodirus species. The specific PCR assay allowed the accurate identification of N. oiratianus from other common nematodes with a sensitivity of 0.69 pg and further examination of Nematodirus samples demonstrated the reliability of these two molecular methods.
Vierna, Joaquín; González-Tizón, Ana M; Martínez-Lage, Andrés
A study of nucleotide sequence variation of 5S ribosomal DNA from six Ensis species revealed that several 5S ribosomal DNA variants, based on differences in their nontranscribed spacers (NTS), occur in Ensis genomes. The 5S rRNA gene was not very polymorphic, compared with the NTS region. The phylogenetic analyses performed showed a between-species clustering of 5S ribosomal DNA variants. Sequence divergence levels between variants were very large, revealing a lack of sequence homogenization. These results strongly suggest that the long-term evolution of Ensis 5S ribosomal DNA is driven by birth-and-death processes and selection.
Simon-Blecher, N; Huchon, D; Achituv, Y
The traditional phylogeny of the coral-inhabiting barnacles, the Pyrgomatidae, is based on morphological characteristics, mainly of the hard parts. It has been difficult to establish the phylogenetic relationships among Pyrgomatidae because of the apparent convergence of morphological characteristics, and due to the use of non-cladistic systematics, which emphasize ancestor-descendant relationships rather than sister-clade relationships. We used partial sequences of two mithochondrial genes, 12S rDNA and 16S rDNA, and a nuclear gene, 18S rDNA, to infer the molecular phylogeny of the pyrgomatids. Our phylogenetic results allowed us to reject previous classifications of Pyrgomatidae based on morphological characteristics. Our results also suggested the possibility of paraphyly of the Pyrgomatidae. The hydrocoral barnacle Wanella is not found on the same clade as the other pyrgomatids, but rather, with the free-living balanids. The basal position of Megatrema and Ceratoconcha is supported. The archeaobalanid Armatobalanus is grouped with Cantellius at the base of the Indo-Pacific pyrgomatines. Fusion of the shell plate and modification of the opercular valves are homoplasious features that occurred more than three times on different clades. The monophyly of the "Savignium" group, comprising four nominal genera, is also not supported, and the different taxa are placed on different clades.
Manichanh, Chaysavanh; Chapple, Charles E; Frangeul, Lionel; Gloux, Karine; Guigo, Roderic; Dore, Joel
The construction of metagenomic libraries has permitted the study of microorganisms resistant to isolation and the analysis of 16S rDNA sequences has been used for over two decades to examine bacterial biodiversity. Here, we show that the analysis of random sequence reads (RSRs) instead of 16S is a suitable shortcut to estimate the biodiversity of a bacterial community from metagenomic libraries. We generated 10,010 RSRs from a metagenomic library of microorganisms found in human faecal samples. Then searched them using the program BLASTN against a prokaryotic sequence database to assign a taxon to each RSR. The results were compared with those obtained by screening and analysing the clones containing 16S rDNA sequences in the whole library. We found that the biodiversity observed by RSR analysis is consistent with that obtained by 16S rDNA. We also show that RSRs are suitable to compare the biodiversity between different metagenomic libraries. RSRs can thus provide a good estimate of the biodiversity of a metagenomic library and, as an alternative to 16S, this approach is both faster and cheaper.
Zhao, Zi-Hua; Cui, Bing-Yi; Li, Zhi-Hong; Jiang, Fan; Yang, Qian-Qian; Kučerová, Zuzana; Stejskal, Václav; Opit, George; Cao, Yang; Li, Fu-Jun
Psocids are important stored product pests found worldwide that can be spread through grain trade. Most stored-product psocids, including eggs, nymphs, and adults, are very small (~1 mm) and difficult to identify morphologically. Here, we collected 10 economically important stored-product Liposcelis spp. psocids (L. bostrychophila, L. entomophila, L. decolor, L. paeta, L. brunnea, L. corrodens, L. mendax, L. rufa, L. pearmani, and L. tricolor) from 35 geographical locations in 5 countries (China, Czech Republic, Denmark, Germany, and the United States). The ITS2 rDNA gene was extracted and sequenced. The interspecific genetic distance of the stored-product psocids was significantly higher than the intraspecific genetic distance according to the barcoding gap analysis. Ten pairs of species-specific primers based on the ITS2 rDNA were developed for psocid identification. The sensitivity estimation indicated that the species-specific primers could correctly amplify the target ITS2 gene and successfully identify psocids at 1.0 ng/mL. Additionally, these species-specific primers could quantify specificity and identify 10 stored-product psocids; this approach could also be used to accurately identify other stored-product psocids. This work provides a practical approach for the precise examination of 10 stored-product psocid species and also contributes to the development of an identification method using ITS2 rDNA.
Sun, Sang-Mi; Yang, Seung Hwan; Golokhvast, Kirill S; Le, Bao; Chung, Gyuhwa
Capsosiphon fulvescens is a filamentous green algae in the class Ulvophyceae. It has been consumed as food with unique flavor and soft texture to treat stomach disorders and hangovers, and its economic value justifies studying its nutritional and potential therapeutic effects. In contrast to these applications, only a few taxonomic studies have been conducted on C. fulvescens. In particular, classification and phylogenetic relationships of the C. fulvescens below the order level are controversial. To determine its phylogenetic position in the class, we used rbcL and 18S rDNA sequences as molecular markers to construct phylogenetic trees. The amplified rbcL and 18S rDNA sequences from 4 C. fulvescens isolates (Jindo, Jangheung, Wando, and Koheung, Korea) were used for phylogenetic analysis by employing three different phylogenetic methods: neighbor joining (NJ), maximum parsimony (MP), and maximum likelihood (ML). The rbcL phylogenetic tree showed that all taxa in the order Ulvales were clustered as a monophyletic group and resolved the phylogenetic position of C. fulvescens in the order Ulotrichales. The significance of our study is that the 18S rDNA phylogenetic tree shows the detailed taxonomic position of C. fulvescens. In our result, C. fulvescens is inferred as a member of Ulotrichaceae, along with Urospora and Acrosiphonia.
Zhao, Zi-Hua; Cui, Bing-Yi; Li, Zhi-Hong; Jiang, Fan; Yang, Qian-Qian; Kučerová, Zuzana; Stejskal, Václav; Opit, George; Cao, Yang; Li, Fu-Jun
Psocids are important stored product pests found worldwide that can be spread through grain trade. Most stored-product psocids, including eggs, nymphs, and adults, are very small (~1 mm) and difficult to identify morphologically. Here, we collected 10 economically important stored-product Liposcelis spp. psocids (L. bostrychophila, L. entomophila, L. decolor, L. paeta, L. brunnea, L. corrodens, L. mendax, L. rufa, L. pearmani, and L. tricolor) from 35 geographical locations in 5 countries (China, Czech Republic, Denmark, Germany, and the United States). The ITS2 rDNA gene was extracted and sequenced. The interspecific genetic distance of the stored-product psocids was significantly higher than the intraspecific genetic distance according to the barcoding gap analysis. Ten pairs of species-specific primers based on the ITS2 rDNA were developed for psocid identification. The sensitivity estimation indicated that the species-specific primers could correctly amplify the target ITS2 gene and successfully identify psocids at 1.0 ng/mL. Additionally, these species-specific primers could quantify specificity and identify 10 stored-product psocids; this approach could also be used to accurately identify other stored-product psocids. This work provides a practical approach for the precise examination of 10 stored-product psocid species and also contributes to the development of an identification method using ITS2 rDNA. PMID:26880378
Waminal, Nomar Espinosa; Park, Hye Mi; Ryu, Kwang Bok; Kim, Joo Hyung; Yang, Tae-Jin; Kim, Hyun Hee
Ginseng has long been considered a valuable plant owing to its medicinal properties; however, genomic information based on chromosome characterization and physical mapping of cytogenetic markers has been very limited. Dual-color FISH karyotype and DAPI banding analyses of Panax ginseng C. A. Meyer, 1843 were conducted using 5S and 45S rDNA probes. The somatic chromosome complement was 2n=48 with lengths from 3.3 μm to 6.3 μm. The karyotype was composed of 12 metacentric, 9 submetacentric, and 3 subtelocentric pairs. The 5S rDNA probe localized to the intercalary region of the short arm of pair 11, while the 45S rDNA was located at the secondary constriction of the subtelocentric satellited chromosome 14. DAPI bands were clearly observed for most chromosomes, with various signal intensities and chromosomal distributions that consequently improved chromosome identification. As a result, all 24 chromosomes could be distinguished and numbers were assigned to each chromosome for the first time. The results presented here will be useful for the on-going ginseng genome sequencing and further molecular-cytogenetic studies and breeding programs of ginseng.
Waminal, Nomar Espinosa; Park, Hye Mi; Ryu, Kwang Bok; Kim, Joo Hyung; Yang, Tae-Jin; Kim, Hyun Hee
Abstract Ginseng has long been considered a valuable plant owing to its medicinal properties; however, genomic information based on chromosome characterization and physical mapping of cytogenetic markers has been very limited. Dual-color FISH karyotype and DAPI banding analyses of Panax ginseng C. A. Meyer, 1843 were conducted using 5S and 45S rDNA probes. The somatic chromosome complement was 2n=48 with lengths from 3.3 μm to 6.3 μm. The karyotype was composed of 12 metacentric, 9 submetacentric, and 3 subtelocentric pairs. The 5S rDNA probe localized to the intercalary region of the short arm of pair 11, while the 45S rDNA was located at the secondary constriction of the subtelocentric satellited chromosome 14. DAPI bands were clearly observed for most chromosomes, with various signal intensities and chromosomal distributions that consequently improved chromosome identification. As a result, all 24 chromosomes could be distinguished and numbers were assigned to each chromosome for the first time. The results presented here will be useful for the on-going ginseng genome sequencing and further molecular-cytogenetic studies and breeding programs of ginseng. PMID:24260682
Amor, Nabil; Halajian, Ali; Farjallah, Sarra; Merella, Paolo; Said, Khaled; Ben Slimane, Badreddine
Fasciolosis caused by Fasciola spp. (Platyhelminthes: Trematoda: Digenea) is considered as the most important helminth infection of ruminants in tropical countries, causing considerable socioeconomic problems. In the endemic regions of the North of Iran, Fasciola hepatica and Fasciola gigantica have been previously characterized on the basis of morphometric differences, but the use of molecular markers is necessary to distinguish exactly between species and intermediate forms. Samples from buffaloes and goats from different localities of northern Iran were identified morphologically and then genetically characterized by sequences of the first (ITS-1) and second (ITS-2) Internal Transcribed Spacers (ITS) of nuclear ribosomal DNA (rDNA). Comparison of the ITS of the northern Iranian samples with sequences of Fasciola spp. from GenBank showed that the examined specimens had sequences identical to those of the most frequent haplotypes of F. hepatica (n=25, 48.1%) and F. gigantica (n=20, 38.45%), which differed from each other in different variable nucleotide positions of ITS region sequences, and their intermediate forms (n=7, 13.45%), which had nucleotides overlapped between the two Fasciola species in all the positions. The ITS sequences from populations of Fasciola isolates in buffaloes and goats had experienced introgression/hybridization as previously reported in isolates from other ruminants and humans. Based on ITS-1 and ITS-2 sequences, flukes are scattered in pure F. hepatica, F. gigantica and intermediate Fasciola clades, revealing that multiple genotypes of Fasciola are able to infect goats and buffaloes in North of Iran. Furthermore, the phylogenetic trees based upon the ITS-1 and ITS-2 sequences showed a close relationship of the Iranian samples with isolates of F. hepatica and F. gigantica from different localities of Africa and Asia. In the present study, the intergenic transcribed spacers ITS-1 and ITS-2 showed to be reliable approaches for the genetic
Hoppenrath, Mona; Bachvaroff, Tsvetan R; Handy, Sara M; Delwiche, Charles F; Leander, Brian S
Background Dinoflagellates represent a major lineage of unicellular eukaryotes with unparalleled diversity and complexity in morphological features. The monophyly of dinoflagellates has been convincingly demonstrated, but the interrelationships among dinoflagellate lineages still remain largely unresolved. Warnowiid dinoflagellates are among the most remarkable eukaryotes known because of their possession of highly elaborate ultrastructural systems: pistons, nematocysts, and ocelloids. Complex organelles like these are evolutionary innovations found only in a few athecate dinoflagellates. Moreover, the taxonomy of warnowiids is extremely confusing and inferences about the evolutionary history of this lineage are mired by the absence of molecular phylogenetic data from any member of the group. In this study, we provide the first molecular phylogenetic data for warnowiids and couple them with a review of warnowiid morphological features in order to formulate a hypothetical framework for understanding character evolution within the group. These data also enabled us to evaluate the evolutionary relationship(s) between warnowiids and the other group of dinoflagellates with complex organelles: polykrikoids. Results Molecular phylogenetic analyses of SSU and LSU rDNA sequences demonstrated that warnowiids form a well-supported clade that falls within the more inclusive Gymnodinium sensu stricto clade. These data also confirmed that polykrikoids are members of the Gymnodinium sensu stricto clade as well; however, a specific sister relationship between the warnowiid clade and the polykrikoid clade was unresolved in all of our analyses. Nonetheless, the new DNA sequences from different isolates of warnowiids provided organismal anchors for several previously unidentified sequences derived from environmental DNA surveys of marine biodiversity. Conclusion Comparative morphological data and molecular phylogenetic data demonstrate that the polykrikoid and the warnowiid clade are
Walkty, Andrew; Embil, John M; Nichol, Kim; Karlowsky, James
Bacteria belonging to the Streptococcus anginosus group (Streptococcus intermedius, Streptococcus constellatus and Streptococcus anginosus) are capable of causing serious pyogenic infections, with a tendency for abscess formation. The present article reports a case of S anginosus group pyomyositis in a 47-year-old man. The pathogen was recovered from one of two blood cultures obtained from the patient, but speciation was initially not performed because the organism was considered to be a contaminant (viridans streptococci group). The diagnosis was ultimately confirmed using 16S ribosomal DNA sequencing of purulent fluid obtained from a muscle abscess aspirate. The present case serves to emphasize that finding even a single positive blood culture of an organism belonging to the S anginosus group should prompt careful evaluation of the patient for a pyogenic focus of infection. It also highlights the potential utility of 16S ribosomal DNA amplification and sequencing in direct pathogen detection from aspirated fluid in cases of pyomyositis in which antimicrobial therapy was initiated before specimen collection.
Choi, In-Wook; Kim, Hwang-Yong; Quan, Juan-Hua; Ryu, Jae-Gee; Sun, Rubing; Lee, Young-Ha
Fascioliasis, a food-borne trematode zoonosis, is a disease primarily in cattle and sheep and occasionally in humans. Water dropwort (Oenanthe javanica), an aquatic perennial herb, is a common second intermediate host of Fasciola, and the fresh stems and leaves are widely used as a seasoning in the Korean diet. However, no information regarding Fasciola species contamination in water dropwort is available. Here, we collected 500 samples of water dropwort in 3 areas in Korea during February and March 2015, and the water dropwort contamination of Fasciola species was monitored by DNA sequencing analysis of the Fasciola hepatica and Fasciola gigantica specific mitochondrial cytochrome c oxidase subunit 1 (cox1) and nuclear ribosomal internal transcribed spacer 2 (ITS-2). Among the 500 samples assessed, the presence of F. hepatica cox1 and 1TS-2 markers were detected in 2 samples, and F. hepatica contamination was confirmed by sequencing analysis. The nucleotide sequences of cox1 PCR products from the 2 F. hepatica-contaminated samples were 96.5% identical to the F. hepatica cox1 sequences in GenBank, whereas F. gigantica cox1 sequences were 46.8% similar with the sequence detected from the cox1 positive samples. However, F. gigantica cox1 and ITS-2 markers were not detected by PCR in the 500 samples of water dropwort. Collectively, in this survey of the water dropwort contamination with Fasciola species, very low prevalence of F. hepatica contamination was detected in the samples.
Yoshizawa, Kazunori; Johnson, Kevin P
Phthiraptera (chewing and sucking lice) and Psocoptera (booklice and barklice) are closely related to each other and compose the monophyletic taxon Psocodea. However, there are two hypotheses regarding their phylogenetic relationship: (1) monophyletic Psocoptera is the sister group of Phthiraptera or (2) Psocoptera is paraphyletic, and Liposcelididae of Psocoptera is the sister group of Phthiraptera. Each hypothesis is supported morphologically and/or embryologically, and this problem has not yet been resolved. In the present study, the phylogenetic position of Phthiraptera was examined using mitochondrial 12S and 16S rDNA sequences, with three methods of phylogenetic analysis. Results of all analyses strongly supported the close relationship between Phthiraptera and Liposcelididae. Results of the present analyses also provided some insight into the elevated rate of evolution in mitochondrial DNA (mtDNA) in Phthiraptera. An elevated substitution rate of mtDNA appears to originate in the common ancestor of Phthiraptera and Liposcelididae, and directly corresponds to an increased G+C content. Therefore, the elevated substitution rate of mtDNA in Phthiraptera and Liposcelididae appears to be directional. A high diversity of 12S rDNA secondary structure was also observed in wide range of Phthiraptera and Liposcelididae, but these structures seem to have evolved independently in different clades.
Rubert, Marceléia; da Rosa, Renata; Zawadzki, Claudio H; Mariotto, Sandra; Moreira-Filho, Orlando; Giuliano-Caetano, Lucia
We investigated the chromosomal distribution of 18S ribosomal DNA (rDNA) in different populations of 11 species of Hypostomus collected in important Brazilian basins, namely South Atlantic, Upper Paraná, and Paraguay applying the fluorescence in situ hybridization (FISH). Hypostomus cochliodon, Hypostomus commersoni, Hypostomus hermanni, Hypostomus regani, Hypostomus albopunctatus, Hypostomus paulinus, Hypostomus aff. paulinus, Hypostomus iheringii, and Hypostomus mutucae presented multiple 18S rDNA sites while Hypostomus strigaticeps and Hypostomus nigromaculatus exhibited a single pair of chromosomes with 18S rDNA sites. The studied species presented variations in the number and position of these sites. The results accomplished were similar to those obtained by the analysis of AgNORs, revealing the same interspecific variability. Each species exhibited distinctive patterns of AgNOR and 18S rDNA distribution, which can be considered cytogenetic markers in each species of the genus and help improve the discussions on the phylogeny of the group.
Crhak Khaitova, Lucie; Werlemark, Gun; Kovarikova, Alena; Nybom, Hilde; Kovarik, Ales
All dogroses (Rosa sect. Caninae) are characterized by the peculiar canina meiosis in which genetic material is unevenly distributed between female and male gametes. The pan-canina rDNA family (termed beta) appears to be conserved in all dogroses analyzed so far. Here, we have studied rDNAs in experimental hybrids obtained from open pollination of F1 plants derived from 2 independent intersectional crosses between the pentaploid dogrose species (2n = 5x = 35) Rosa rubiginosa as female parent (producing 4x egg cells due to the unique asymmetrical canina meiosis) and the tetraploid (2n = 4x = 28) garden rose R. hybrida 'André Brichet' as male parent (producing 2x pollen after normal meiosis). We analyzed the structure of rDNA units by molecular methods [CAPS and extensive sequencing of internal transcribed spacers (ITS)] and determined the number of loci on chromosomes by FISH. FISH showed that R. rubiginosa and 'André Brichet' harbored 5 and 4 highly heteromorphic rDNA loci, respectively. In the second generation of hybrid lines, we observed a reduced number of loci (4 and 5 instead of the expected 6). In R. rubiginosa and 'André Brichet', 2-3 major ITS types were found which is consistent with a weak homogenization pressure maintaining high diversity of ITS types in this genus. In contrast to expectation (the null hypothesis of Mendelian inheritance of ITS families), we observed reduced ITS diversity in some individuals of the second generation which might derive from self-fertilization or from a backcross to R. rubiginosa. In these individuals, the pan-canina beta family appeared to be markedly enriched, while the paternal families were lost or diminished in copies. Although the mechanism of biased meiotic transmission of certain rDNA types is currently unknown, we speculate that the bivalent-forming chromosomes carrying the beta rDNA family exhibit extraordinary pairing efficiency and/or are subjected to strong selection in Caninae polyploids.
McColl, J. L.; Couto, J.; Bendle, J. A.; Henderson, A. C.; Seki, O.; Phoenix, V. R.; Toney, J. L.
Alkenones (long chain ketones) are readily preserved in sedimentary archives and have the potential to provide quantitative reconstructions of past water temperature. Alkenones are produced by a limited number of haptophyte algae in the marine and also some lacustrine systems. However, lakes are heterogeneous: an individual lake will have a unique combination of ecological conditions, haptophyte species and seasonal alkenone production that contributes to the sedimentary record. Haptophyte algae species have different sensitivities to temperature; therefore identifying the alkenone producer(s) prior to down-core temperature reconstructions is critical before selecting the most appropriate temperature calibration. We present a study from Lake Toyoni, a freshwater lake in Hokkaido, Japan that has alkenones preserved in surface sediments. The aim of this study is to identify the alkenone producer(s) within the lake using 18S rDNA analyses. Preserved rDNA of planktonic phototrophic algae was extracted from surface sediments of Lake Toyoni and phylogenetic analyses of the rDNA sequences suggest alkenones are produced by a single haptophyte within the class Prymnesiophyceae (order Isochrysidales). The Lake Toyoni alkenone-producer shares a distinct phylotype with a haptophyte reported from water filter samples collected in Lake BrayaSø, Greenland (D'Andrea et al., 2006). Similarity between the 18S rDNA sequences from Lake Toyoni and Lake BrayaSø provides a basis for applying (and updating) the Greenland lake temperature calibration. Applying this temperature calibration (T°C = 40.8 [UK37] + 31.8, R2=0.96; n=34) to the surface sediment alkenone unsaturation index from Lake Toyoni gives an estimated lake surface temperature (LST) of 8°C. This is in line with observed LST at Lake Toyoni, which ranges between 7 - 22°C (Apr 2011 to Nov 2011). The occurrence and identification of a single alkenone producer in Lake Toyoni means problems posed by a mixture of haptophytes in
Masih, Shet; Arora, Sunil K; Vasishta, Rakesh K
The acidic ribosomal proteins of the protozoan parasites have been described as prominent antigens during human disease. We present here data showing the molecular cloning and protective efficacy of P1 gene of Leishmania donovani as DNA vaccine. The PCR amplified complete ORF cloned in either pQE or pVAX vector was used either as peptide or DNA vaccine against experimentally induced visceral leishmaniasis in hamsters. The recombinant protein rLdP1 was given along with Freund's adjuvant and the plasmid DNA vaccine, pVAX-P1 was used alone either as single dose or double dose (prime and boost) in different groups of hamsters which were subsequently challenged with a virulent dose of 1×10(7) L. donovani (MHOM/IN/DD8/1968 strain) promastigotes by intra-cardiac route. While the recombinant protein rLdP1 or DNA vaccine pVAX-P1 in single dose format were not found to be protective, DNA vaccine in a prime-boost mode was able to induce protection with reduced mortality, a significant (75.68%) decrease in splenic parasite burden and increased expression of Th1 type cytokines in immunized hamsters. Histopathology of livers and spleens from these animals showed formation of mature granulomas with compact arrangement of lymphocytes and histiocytes, indicating its protective potential as vaccine candidate.
Felsberg, Jurgen; Jelínková, Markéta; Kubizniaková, Petra; Matoulková, Dagmar
PCR-primers were designed for identification of strictly anaerobic bacteria of the genus Zymophilus based on genus-specific sequences of the 16S-23S rDNA internal transcribed spacer region. The specificity of the primers was tested against 37 brewery-related non-target microorganisms that could potentially occur in the same brewery specimens. None DNA was amplified from any of the non-Zymophilus strains tested including genera from the same family (Pectinatus, Megasphaera, Selenomonas), showing thus 100% specificity. PCR assay developed in this study allows an extension of the spectra of detected beer spoilage microorganisms in brewery laboratories.
von Nickisch-Rosenegk, M; Silva-Gonzalez, R; Lucius, R
The construction of new specific tapeworm primers allowed synthesis of a 311-bp fragment of the mitochondrial 12S rDNA of 11 Taenia species and two Echinococcus species by PCR. After direct sequencing and construction of an alignment, the DNA sequences were calculated by three different phylogenetic algorithms. The phylogenetic trees were tested by 1000 bootstrap replications. Reliability of the nodes was tested by splits testing. All three algorithms revealed a clear monophyletic phylum Taenia, suggesting it may be paraphyletic with respect to the genus Echinococcus. Within the genus Taenia, the first secure group was composed by Taenia saginata, T. solium, T. serialis, T. ovis and T. hydatigena. A delimited second group was formed by T. martis, T. taeniaeformis, T. mustelae and T. parva. All of them were opposed to the genus Echinococcus using other cyclophyllideans as an outgroup. In this study Echinococcus was used as an outgroup, being the closest species against which the ingroup could be routed. The findings of this publication reflect Verster's basic morphologically based grouping of the Taeniidae.
Mattos, Viviane Fagundes; Carvalho, Leonardo Sousa; Cella, Doralice Maria; Schneider, Marielle Cristina
Buthid scorpions exhibit a high variability in diploid number within genera and even within species. Cytogenetically, Buthidae differs from other families of Scorpiones based on its low diploid numbers, holocentric chromosomes, and complex chromosomal chains, which form during meiosis. In this study, we analyzed the distribution of the 45S ribosomal DNA (rDNA) genes in the mitotic and meiotic chromosomes of seven buthid species belonging to the genera Rhopalurus and Tityus with the ultimate goal of elucidating the chromosome organization in these scorpions. The chromosome number ranged from 2n=6 to 2n=28. Despite the high variance in diploid number, all species examined carried their 45S rDNA sites in the terminal region of exactly two chromosomes. Analyses of meiotic cells revealed 45S rDNA clusters in the chromosomal chains of Rhopalurus agamemnon, Tityus bahiensis, Tityus confluens, and Tityus martinpaechi, or in bivalent-like configuration in Rhopalurus rochai, Tityus bahiensis, Tityus confluens, Tityus fasciolatus, and Tityus paraguayensis. In the species examined, the 45S rDNA sites colocalized with constitutive heterochromatin regions. In light of the high chromosome variability and maintenance of number and terminal position of 45S rDNA sites in buthids, the heterochromatin may act to conserve the integrity of the ribosomal genes.
Moreira, David; Rodríguez-Valera, Francisco; López-García, Purificación
We have sequenced and analysed a 39.5 kbp genome fragment of a marine Group II euryarchaeote identified in a metagenomic library of 500 m deep plankton at the Antarctic Polar Front. The clone contains a 16S rRNA gene that is separated from the 23S rRNA gene in the genome. This appears to be a trait shared by Thermoplasmatales and Group II euryarchaeota. This genome fragment exhibits a compact organization, including a few overlapping genes in the canonical spectinomycin-like (spc) operon for ribosomal proteins that is immediately upstream the 16S rDNA. Most open reading frames (ORFs) encoded proteins involved in housekeeping processes and, as expected, exhibited a phylogenetic distribution congruent with that of the 16S rRNA. A considerable number of proteins with predicted transmembrane helices was identified. Among those, two proteins encoded by genes likely forming an operon appear to be part of a membrane terminal electron transport chain. One of these proteins has an unusual domain arrangement including ferredoxin, flavodoxin and one succinate dehydrogenase/fumarate reductase subunit. These proteins probably constitute a new succinate dehydrogenase-like oxidoreductase involved in what could be a novel pathway for energy metabolism in Group II euryarchaeota.
To prevent illegal fishing and sale, the most difficult problem is identification of marketed fish species, especially the parts that are difficult to be differentiated with morphological method (e.g., larval, eggs, scales, meat, products etc. To assist conservation and management of fishery resources, this paper reported a molecular genetic approach based on ribosomal internal transcribed spacer 2 locus. The method includes two steps: (1) the order general primers were designed according to the conservative nature of 5.8SrRAN and 28SrRNA genes within an order, and the DNA ribosomal internal transcribed spacer 2 locus fragment were then amplified and sequenced. (2) The species-specific ladders and the species-specific primers for each species were designed according to the sequencing results. The map of molecular taxonomy was constructed. This approach employs multiplex PCR that is formatted for fish species identification. We tested 210 single-species samples and 40 mix-species samples from different regions of China. The approach distinguished accurately and sensitively samples from each of the five species. This genetic and molecular approach will be useful for fish conservation, assessment, management and exploitation, strengthen in law enforcement of fishery manager, combat rare and endangered fish smuggling, and prevent commercial fraud and biological invasion by harmful nonnative species.
Wang, Shuzhen; Zheng, Yinzhen; Yan, Junjie; Zhu, Zhixuan; Wu, Zhihua; Ding, Yi
Ribosome-inactivating proteins (RIPs) function to inhibit protein synthesis through the removal of specific adenine residues from eukaryotic ribosomal RNA and rending the 60S subunit unable to bind elongation factor 2. They have received much attention in biological and biomedical research due to their unique activities toward tumor cells, as well as the important roles in plant defense. Alpha-momorcharin (α-MC), a member of the type I family of RIPs, is rich in the seeds of Momordica charantia L. Previous studies demonstrated that α-MC is an effective antifungal and antibacterial protein. In this study, a detailed analysis of the DNase-like activity of α-MC was conducted. Results showed that the DNase-like activity toward plasmid DNA was time-dependent, temperature-related, and pH-stable. Moreover, a requirement for divalent metal ions in the catalytic domain of α-MC was confirmed. Additionally, Tyr(93) was found to be a critical residue for the DNase-like activity, while Tyr(134), Glu(183), Arg(186), and Trp(215) were activity-related residues. This study on the chemico-physical properties and mechanism of action of α-MC will improve its utilization in scientific research, as well as its potential industrial uses. These results may also assist in the characterization and elucidation of the DNase-like enzymatic properties of other RIPs.
Maggini, F; Cremonini, R; Zolfino, C; Tucci, G F; D'Ovidio, R; Delre, V; DePace, C; Scarascia Mugnozza, G T; Cionini, P G
Subrepeating sequences of 325 bp found in the ribosomal intergenic spacer (IGS) of Vicia faba and responsible for variations in the length of the polycistronic units for rRNA were isolated and used as probes for in situ hybridization. Hybridization occurs at many regions of the metaphase chromosomes besides those bearing rRNA genes, namely chromosome ends and all the heterochromatic regions revealed by enhanced fluorescence after quinacrine staining. The DNA homologous to the 325 bp repeats that does not reside in the IGS was isolated, cloned and sequenced. It is composed of tandemly arranged 336 bp elements, each comprising two highly related 168 bp sequences. This structure is very similar to that of the IGS repeats and ca. 75% nucleotide sequence identity can be observed between these and the 168 bp doublets. The most obvious difference lies in the deletion, in the former, of a 14 bp segment from one of the two related sequences. It is hypothesized that the IGS repeats are derived from the 336 bp elements and have been transposed to ribosomal cistrons from other genome fractions. The possible relations between these sequences and others with similar structural features found in other species are discussed.
Garcia, S; Kovařík, A
In higher eukaryotes, the 5S rRNA genes occur in tandem units and are arranged either separately (S-type arrangement) or linked to other repeated genes, in most cases to rDNA locus encoding 18S–5.8S–26S genes (L-type arrangement). Here we used Southern blot hybridisation, PCR and sequencing approaches to analyse genomic organisation of rRNA genes in all large gymnosperm groups, including Coniferales, Ginkgoales, Gnetales and Cycadales. The data are provided for 27 species (21 genera). The 5S units linked to the 35S rDNA units occur in some but not all Gnetales, Coniferales and in Ginkgo (∼30% of the species analysed), while the remaining exhibit separate organisation. The linked 5S rRNA genes may occur as single-copy insertions or as short tandems embedded in the 26S–18S rDNA intergenic spacer (IGS). The 5S transcript may be encoded by the same (Ginkgo, Ephedra) or opposite (Podocarpus) DNA strand as the 18S–5.8S–26S genes. In addition, pseudogenised 5S copies were also found in some IGS types. Both L- and S-type units have been largely homogenised across the genomes. Phylogenetic relationships based on the comparison of 5S coding sequences suggest that the 5S genes independently inserted IGS at least three times in the course of gymnosperm evolution. Frequent transpositions and rearrangements of basic units indicate relatively relaxed selection pressures imposed on genomic organisation of 5S genes in plants. PMID:23512008
Garcia, S; Kovařík, A
In higher eukaryotes, the 5S rRNA genes occur in tandem units and are arranged either separately (S-type arrangement) or linked to other repeated genes, in most cases to rDNA locus encoding 18S-5.8S-26S genes (L-type arrangement). Here we used Southern blot hybridisation, PCR and sequencing approaches to analyse genomic organisation of rRNA genes in all large gymnosperm groups, including Coniferales, Ginkgoales, Gnetales and Cycadales. The data are provided for 27 species (21 genera). The 5S units linked to the 35S rDNA units occur in some but not all Gnetales, Coniferales and in Ginkgo (∼30% of the species analysed), while the remaining exhibit separate organisation. The linked 5S rRNA genes may occur as single-copy insertions or as short tandems embedded in the 26S-18S rDNA intergenic spacer (IGS). The 5S transcript may be encoded by the same (Ginkgo, Ephedra) or opposite (Podocarpus) DNA strand as the 18S-5.8S-26S genes. In addition, pseudogenised 5S copies were also found in some IGS types. Both L- and S-type units have been largely homogenised across the genomes. Phylogenetic relationships based on the comparison of 5S coding sequences suggest that the 5S genes independently inserted IGS at least three times in the course of gymnosperm evolution. Frequent transpositions and rearrangements of basic units indicate relatively relaxed selection pressures imposed on genomic organisation of 5S genes in plants.
Ajitkumar, Praseeda; Barkema, Herman W; De Buck, Jeroen
Accurate identification of mastitis pathogens is often compromised when using conventional culture-based methods. Here, we report a novel, rapid assay tested for speciation of bacterial mastitis pathogens using high-resolution melt analysis (HRMA) of 16S rDNA sequences. Real-time PCR amplification of 16S rRNA gene fragment, spanning the variable region V5 and V6 was performed with a resulting amplicon of 290bp. First, a library was generated of melt curves of 9 common pathogens that are implicated in bovine mastitis. Six of the isolates, Escherichia coli, Streptococcus agalactiae, Klebsiella pneumoniae, Streptococcus uberis, Staphylococcus aureus and Mycoplasma bovis, were type strains while the other 3, Arcanobacterium pyogenes, Corynebacterium bovis and Streptococcus dysgalactiae, were bovine mastitis field isolates. Four of the type strains, E. coli, S. agalactiae, K. pneumoniae and S. aureus, were found to be of human origin, while the other 3 type strains were isolated from bovine infections. Secondly, the melt curves and corresponding amplicon sequences of A. pyogenes, E. coli, S. agalactiae, S. dysgalactiae, K. pneumoniae, S. uberis and S. aureus were compared with 10 bovine mastitis field isolates of each pathogen. Based on the distinct differences in melt curves and sequences between human and bovine isolates of E. coli and K. pneumoniae, it was deemed necessary to select a set of bovine strains for these pathogens to be used as reference strains in the HRMA. Next, the HRMA was validated by three interpreters analyzing the differential clustering pattern of melt curves of 60 bacterial cultures obtained from mastitis milk samples. The three test interpreters were blinded to the culture and sequencing results of the isolates. Overall accuracy of the validation assay was 95% as there was difficulty in identifying the streptococci due to heterogeneity observed in the PCR amplicons of S. uberis. The present study revealed that broad-range real-time PCR with
Pita, Sebastián; Panzera, Francisco; Ferrandis, Inés; Galvão, Cleber; Gómez-Palacio, Andrés; Panzera, Yanina
In this study, we used fluorescence in situ hybridisation to determine the chromosomal location of 45S rDNA clusters in 10 species of the tribe Rhodniini (Hemiptera: Reduviidae: Triatominae). The results showed striking inter and intraspecific variability, with the location of the rDNA clusters restricted to sex chromosomes with two patterns: either on one (X chromosome) or both sex chromosomes (X and Y chromosomes). This variation occurs within a genus that has an unchanging diploid chromosome number (2n = 22, including 20 autosomes and 2 sex chromosomes) and a similar chromosome size and genomic DNA content, reflecting a genome dynamic not revealed by these chromosome traits. The rDNA variation in closely related species and the intraspecific polymorphism in Rhodnius ecuadoriensis suggested that the chromosomal position of rDNA clusters might be a useful marker to identify recently diverged species or populations. We discuss the ancestral position of ribosomal genes in the tribe Rhodniini and the possible mechanisms involved in the variation of the rDNA clusters, including the loss of rDNA loci on the Y chromosome, transposition and ectopic pairing. The last two processes involve chromosomal exchanges between both sex chromosomes, in contrast to the widely accepted idea that the achiasmatic sex chromosomes of Heteroptera do not interchange sequences. PMID:23778665
Rivera, Windell L; Adao, Davin Edric V
This study was carried out to document the genotypes of Acanthamoeba present in contact lens cases from 50 randomly selected contact lens wearers living in Quezon City, Metro Manila, Philippines. Acanthamoeba species were isolated from eight (16%) in 50 contact lens cases examined. We analyzed partial 18S ribosomal DNA (Rns) sequences of the eight isolates and found that the sequence differences were sufficient to distinguish the genotypes. After the isolates were genotyped, using the Basic Local Alignment Search Tool program, their phylogenetic positions relative to known Acanthamoeba isolates were determined. The model-based (GTR+Gamma+Iota) neighbor-joining, maximum likelihood, and Bayesian inference analyses, as well as the non-model-based maximum parsimony analysis were used. Results showed that of the eight isolates, six were Rns genotype T5 while two were Rns genotype T4. This present study indicates that genotype T5 is also a common contaminant in contact lens storage cases.
Silberman, J D; Walsh, P J
Within the tropical northwestern Atlantic, Panulirus argus, P. guttatus, and P. laevicauda (Palinuridae family), are sympatric. Numerous studies have examined the distribution and abundance of planktonic phyllosome larvae with respect to recruitment of spiny lobsters to the benthic population, but the data are of limited use because larvae of these species cannot yet be distinguished from one another by morphological characteristics. A simple molecular method that unambiguously differentiates adults or larvae of P. argus, P. guttatus, and P. laevicauda is described: a 5' region of 28s ribosomal DNA is amplified in vitro and then cut with a diagnostic restriction enzyme to identify each species. Data are also presented from the application of this method to representative plankton tows.
Warberg, Rikke; Jensen, K Thomas; Frydenberg, Jane
In searching for species-specific DNA sequences of microphallid species (Digenea, Trematoda) we examined the ribosomal internal transcribed spacer regions (ITS) of three closely related species (Levinseniella group) hosted by mud snails (first intermediate host) and marine crustaceans (second intermediate host). In the ITS1 region we found consistent patterns of repeating sequences of 130 bp. Within each main repeat there was a varying number of subrepeats specific for each of the species. All repeats including subrepeats were identified by a similar starting sequence: 5'-CCTGTGG-3'. As this sequence has close resemblance to the chi sequence 5'-GCTGGTGG-3' found in phage lambda we speculate if it serves the same function as a recombination hotspot. Alternatively but less likely, it could be an inactive, mutational relic of a sequence that once served this purpose.
Cockroaches are among the most ancient winged insects, the earliest fossils dating back to about 400 million years. Several conflicting phylogenies for cockroach families, subfamilies, and genera have been proposed in the past. In addition, the relationship of Cryptocercidae to other cockroach families and the relationship between the cockroach, Cryptocercus punctulatus, and the termite, Mastotermes darwiniensis, have generated debate. In this paper, a phylogeny for cockroaches, mantids, and termites based on DNA sequence of the mitochondrial ribosomal RNA genes is presented. The results indicated that cockroaches are a monophyletic group, whose sister group is Mantoidea. The inferred relationship among cockroach families was in agreement with the presently accepted phylogeny. However, there was only partial congruence at the subfamily and the generic levels. The phylogeny inferred here does not support a close relationship between C. punctulatus and M. darwiniensis. The apparent synapomorphies of these two species are likely a manifestation of convergent evolution because there are similarities in biology and habitat. PMID:7534409
Tatonova, Yulia V; Chelomina, Galina N; Besprosvannykh, Vladimir V
The present study examined the molecular organisation and sequence variation in the nuclear ribosomal DNA (rDNA) region, including the two internal transcribed spacers (ITS1 and ITS2) and the 5.8S gene of the Clonorchis sinensis from the Russian Far East. The relevant sequences from other parts of this species' area were downloaded from GenBank. The results showed 100% identity for all investigated 5.8S-ITS2 rDNA sequences. In contrast, two levels of intraspecific variations were revealed in the complete ITS1 sequences. The intra-genomic variation resulted from a C/T polymorphism in a single position. The inter-individual differences between the ITS1 sequences were both due to nucleotide and size polymorphisms resulting from a varying number of five-nucleotide repeats and followed by two ITS1 length variants. These variant frequencies correlate with the clonorchiasis level in some geographical localities. ITS1 differences, both in the mutation profile and mutation localisation, were revealed between northern and southern geographical samples. The presence of GC boxes that are identical to known regulatory motifs in eukaryotes was detected within the ITS1 sub-repeats. The predicted secondary structures for ITS1 consist of two large branches, one of which was invariable, while another depended on ITS1 length. The predicted secondary structure for ITS2 includes four helices around the core. The main differences between C. sinensis and other opisthorchids were localised on the tops of helices 2, 3, and 4. A phylogenetic MST reconstruction subdivided all ITS1 sequences into two well differentiated clusters, each with the major widespread ribotype, and showed that ribotype diversity in both Russia and Korea is much lower than in China. The results obtained demonstrate the feasibility of complete ITS1 sequences in C. sinensis population genetics and can be considered as a basis for further studies of the parasite infection because they may help to elucidate the molecular
Athokpam, Voleentina D; Jyrwa, Donald B; Tandon, Veena
Freshwater fishes in Manipur, Northeast India frequently harbour several types of metacercariae, which based on morphological criteria were identified as Clinostomoides brieni, Euclinostomum heterostomum (Clinostomidae) and Polylekithum sp. (Allocreadiidae). Molecular techniques utilizing PCR amplification of rDNA regions of larger subunit (LSU or 28S), smaller subunit (SSU or 18S) and inter transcribed spacers (ITS1, 2) were used for molecular characterization of these types. Sequences generated from the metacercariae were compared with their related sequences available in public databases; an analysis of the identity matrices and phylogenetic trees constructed was also carried out, which confirmed their identification. Similarly, the sequences generated from Polylekithum sp. were found to be highly similar to the species of the same genus. The rDNA ITS2 secondary structure provided additional confirmation of the robustness of the molecular marker as a tool for taxon-specific characterization.
Wu, G-F; Hou, Y-L; Hou, W-R; Song, Y; Zhang, T
RPS14 is a component of the 40S ribosomal subunit encoded by the RPS14 gene and is required for its maturation. The cDNA and the genomic sequence of RPS14 were cloned successfully from the giant panda (Ailuropoda melanoleuca) using RT-PCR technology and touchdown-PCR, respectively; they were both sequenced and analyzed. The length of the cloned cDNA fragment was 492 bp; it contained an open-reading frame of 456 bp, encoding 151 amino acids. The length of the genomic sequence is 3421 bp; it contains four exons and three introns. Alignment analysis indicates that the nucleotide sequence shares a high degree of homology with those of Homo sapiens, Bos taurus, Mus musculus, Rattus norvegicus, Gallus gallus, Xenopus laevis, and Danio rerio (93.64, 83.37, 92.54, 91.89, 87.28, 84.21, and 84.87%, respectively). Comparison of the deduced amino acid sequences of the giant panda with those of these other species revealed that the RPS14 of giant panda is highly homologous with those of B. taurus, R. norvegicus and D. rerio (85.99, 99.34 and 99.34%, respectively), and is 100% identical with the others. This degree of conservation of RPS14 suggests evolutionary selection. Topology prediction shows that there are two N-glycosylation sites, three protein kinase C phosphorylation sites, two casein kinase II phosphorylation sites, four N-myristoylation sites, two amidation sites, and one ribosomal protein S11 signature in the RPS14 protein of the giant panda. The RPS14 gene can be readily expressed in Escherichia coli. When it was fused with the N-terminally His-tagged protein, it gave rise to accumulation of an expected 22-kDa polypeptide, in good agreement with the predicted molecular weight. The expression product obtained can be purified for studies of its function.
Docker, M F; Kent, M L; Hervio, D M; Khattra, J S; Weiss, L M; Cali, A; Devlin, R H
Rules of zoological nomenclature, morphological data, and ribosomal DNA sequence data support the validity of the genus Nucleospora, and its placement in the family Enterocytozoonidae. Although Nucleospora exhibits most of the distinguishing morphological characteristics of the family Enterocytozoonidae Cali and Owen, 1990, the distinctively different hosts (fish and humans, respectively) and sites of development (the nuclei of immature blood cells and the cytoplasm of enterocytes) support the placement of Nucleospora and Enterocytozoon into separate genera. Ribosomal DNA sequence comparisons between Nucleospora salmonis and Enterocytozoon bieneusi showed 19.8% genetic divergence in the large and small subunit regions. Although more inter- and intrageneric comparisons are needed before percent homology of ribosomal DNA can be used as a criterion for the separation of genera, the genetic divergence between the two species is sufficiently large to deter suppression of the genus Nucleospora as a junior synonym of Enterocytozoon. A polymerase chain reaction test for the detection of N. salmonis in chinook salmon (Oncorhynchus tshawytscha), based on N. salmonis-specific ribosomal DNA sequence, is described.
Marilley, M; Radebaugh, C A; Geiss, G K; Laybourn, P J; Paule, M R
Eukaryotic ribosomal RNA promoters exhibit an unusual conservation of non-canonical DNA structure (curvature, twist angle and duplex stability) despite a lack of primary sequence conservation. This raises the possibility that rRNA transcription factors might utilize structural anomalies in their sequence recognition process. We have analyzed in detail the interaction of the polymerase I transcription factor TIF-IB from Acanthmoeba castellanii with the CORE promoter. TIF-IB interacts primarily with the minor groove of the promoter. By correlating the effects on transcription and on DNA structure of promoter point mutations, we show that the TIF-IB interaction is strongly inhibited by increases in minor groove width. This suggests that a particular DNA structure is required for interaction with the transcription factor. In addition, TIF-IB induces a small bend in the promoter upon binding. Modeling of this bend reveals that it requires an additional narrowing of the minor groove, which would favor binding to mutants with narrower grooves. We also discuss how this narrowing would induce a small destabilization of the helix upstream of the transcription start site. Telestability predicts this would result in destabilization of the sequence that melts during initiation, suggesting that TIF-IB may have a role in stimulating melting.
Elbrecht, Vasco; Taberlet, Pierre; Dejean, Tony; Valentini, Alice; Usseglio-Polatera, Philippe; Beisel, Jean-Nicolas; Coissac, Eric; Boyer, Frederic
Cytochrome c oxidase I (COI) is a powerful marker for DNA barcoding of animals, with good taxonomic resolution and a large reference database. However, when used for DNA metabarcoding, estimation of taxa abundances and species detection are limited due to primer bias caused by highly variable primer binding sites across the COI gene. Therefore, we explored the ability of the 16S ribosomal DNA gene as an alternative metabarcoding marker for species level assessments. Ten bulk samples, each containing equal amounts of tissue from 52 freshwater invertebrate taxa, were sequenced with the Illumina NextSeq 500 system. The 16S primers amplified three more insect species than the Folmer COI primers and amplified more equally, probably due to decreased primer bias. Estimation of biomass might be less biased with 16S than with COI, although variation in read abundances of two orders of magnitudes is still observed. According to these results, the marker choice depends on the scientific question. If the goal is to obtain a taxonomic identification at the species level, then COI is more appropriate due to established reference databases and known taxonomic resolution of this marker, knowing that a greater proportion of insects will be missed using COI Folmer primers. If the goal is to obtain a more comprehensive survey the 16S marker, which requires building a local reference database, or optimised degenerated COI primers could be more appropriate. PMID:27114891
Tolba, Ola; Earle, J A Philip; Millar, B Cherie; Rooney, Paul J; Moore, John E
Phenotypic speciation of foodborne Bacillus spp. remains problematic in terms of obtaining a reliable identification. In this study, we wished to identify several bacterial isolates from honey produced in Northern Ireland, and which belonged to the genus Bacillus, through employment of a molecular identification scheme based on PCR amplification of universal regions of the 16S rRNA operon in combination with direct automated sequencing of the resulting amplicons. Seven samples of honey and related materials (propolis) were examined microbiologically and were demonstrated to have total viable counts (TVC) ranging from <100 to 1700 colony-forming units/g. No yeasts or filamentous fungi were isolated from the honey materials. Several bacterial isolates were identified using this method, yielding two different genera (Paenibacillus and Bacillus), as well as four Bacillus species, namely Bacillus pumilus, B. licheniformis, B. subtilis and B. fusiformis, with B. pumilus the most frequently identified species present. When the use of molecular identification methods is justified, employment of partial 16S rDNA PCR and sequencing provides a valuable and reliable method of identification of Bacillus spp. from foodstuffs and negates associated problems of conventional laboratory and phenotypic identification.
Stoeck, T; Przybos, E; Dunthorn, M
Ciliates are a major evolutionary lineage within the alveolates, which are distributed in nearly all habitats on our planet and are an essential component for ecosystem function, processes and stability. Accurate identification of these unicellular eukaryotes through, for example, microscopy or mating type reactions is reserved to few specialists. To satisfy the demand for a DNA barcode for ciliates, which meets the standard criteria for DNA barcodes defined by the Consortium for the Barcode of Life (CBOL), we here evaluated the D1-D2 region of the ribosomal DNA large subunit (LSU-rDNA). Primer universality for the phylum Ciliophora was tested in silico with available database sequences as well as in the laboratory with 73 ciliate species, which represented nine of 12 ciliate classes. Primers tested in this study were successful for all tested classes. To test the ability of the D1-D2 region to resolve conspecific and congeneric sequence divergence, 63 Paramecium strains were sampled from 24 mating species. The average conspecific D1-D2 variation was 0.18%, whereas congeneric sequence divergence averaged 4.83%. In pairwise genetic distance analyses, we identified a D1-D2 sequence divergence of <0.6% as an ideal threshold to discriminate Paramecium species. Using this definition, only 3.8% of all conspecific and 3.9% of all congeneric sequence comparisons had the potential of false assignments. Neighbour-joining analyses inferred monophyly for all taxa but for two Paramecium octaurelia strains. Here, we present a protocol for easy DNA amplification of single cells and voucher deposition. In conclusion, the presented data pinpoint the D1-D2 region as an excellent candidate for an official CBOL barcode for ciliated protists.
Jin, Dong-Pil; Lee, Jung-Hyun; Xu, Bo; Choi, Byoung-Hee
The dynamic changes in land configuration during the Quaternary that were accompanied by climatic oscillations have significantly influenced the current distribution and genetic structure of warm-temperate forests in East Asia. Although recent surveys have been conducted, the historical migration of forest species via land bridges and, especially, the origins of Korean populations remains conjectural. Here, we reveal the genetic structure of Lespedeza buergeri, a warm-temperate shrub that is disjunctively distributed around the East China Sea (ECS) at China, Korea, and Japan. Two non-coding regions (rpl32-trnL, psbA-trnH) of chloroplast DNA (cpDNA) and the internal transcribed spacer of nuclear ribosomal DNA (nrITS) were analyzed for 188 individuals from 16 populations, which covered almost all of its distribution. The nrITS data demonstrated a genetic structure that followed geographic boundaries. This examination utilized AMOVA, comparisons of genetic differentiation based on haplotype frequency/genetic mutations among haplotypes, and Mantel tests. However, the cpDNA data showed contrasting genetic pattern, implying that this difference was due to a slower mutation rate in cpDNA than in nrITS. These results indicated frequent migration by this species via an ECS land bridge during the early Pleistocene that then tapered gradually toward the late Pleistocene. A genetic isolation between western and eastern Japan coincided with broad consensus that was suggested by the presence of other warm-temperate plants in that country. For Korean populations, high genetic diversity indicated the existence of refugia during the Last Glacial Maximum on the Korean Peninsula. However, their closeness with western Japanese populations at the level of haplotype clade implied that gene flow from western Japanese refugia was possible until post-glacial processing occurred through the Korea/Tsushima Strait land bridge.
Negrisolo, Enrico; Maistro, Silvia; Incarbone, Matteo; Moro, Isabella; Dalla Valle, Luisa; Broady, Paul A; Andreoli, Carlo
Xanthophyceae are a group of heterokontophyte algae. Few molecular studies have investigated the evolutionary history and phylogenetic relationships of this class. We sequenced the nuclear-encoded SSU rDNA and chloroplast-encoded rbcL genes of several xanthophycean species from different orders, families, and genera. Neither SSU rDNA nor rbcL genes show intraspecific sequence variation and are good diagnostic markers for characterization of problematic species. New sequences, combined with those previously available, were used to create different multiple alignments. Analyses included sequences from 26 species of Xanthophyceae plus three Phaeothamniophyceae and two Phaeophyceae taxa used as outgroups. Phylogenetic analyses were performed according to Bayesian inference, maximum likelihood, and maximum parsimony methods. We explored effects produced on the phylogenetic outcomes by both taxon sampling as well as selected genes. Congruent results were obtained from analyses performed on single gene multiple alignments as well as on a data set including both SSU rDNA and rbcL sequences. Trees obtained in this study show that several currently recognized xanthophycean taxa do not form monophyletic groups. The order Mischococcales is paraphyletic, while Tribonematales and Botrydiales are polyphyletic even if evidence for the second order is not conclusive. Botrydiales and Vaucheriales, both including siphonous taxa, do not form a clade. The families Botrydiopsidaceae, Botryochloridaceae, and Pleurochloridaceae as well as the genera Botrydiopsis and Chlorellidium are polyphyletic. The Centritractaceae and the genus Bumilleriopsis also appear to be polyphyletic but their monophyly cannot be completely rejected with current evidence. Our results support morphological convergence at any taxonomic rank in the evolution of the Xanthophyceae. Finally, our phylogenetic analyses exclude an origin of the Xanthophyceae from a Vaucheria-like ancestor and favor a single early origin
Martoni, Francesco; Eickbush, Danna G; Scavariello, Claudia; Luchetti, Andrea; Mantovani, Barbara
R2 is an extensively investigated non-LTR retrotransposon that specifically inserts into the 28S rRNA gene sequences of a wide range of metazoans, disrupting its functionality. During R2 integration, first strand synthesis can be incomplete so that 5' end deleted copies are occasionally inserted. While active R2 copies repopulate the locus by retrotransposing, the non-functional truncated elements should frequently be eliminated by molecular drive processes leading to the concerted evolution of the rDNA array(s). Although, multiple R2 lineages have been discovered in the genome of many animals, the rDNA of the stick insect Bacillus rossius exhibits a peculiar situation: it harbors both a canonical, functional R2 element (R2Brfun) as well as a full-length but degenerate element (R2Brdeg). An intensive sequencing survey in the present study reveals that all truncated variants in stick insects are present in multiple copies suggesting they were duplicated by unequal recombination. Sequencing results also demonstrate that all R2Brdeg copies are full-length, i. e. they have no associated 5' end deletions, and functional assays indicate they have lost the active ribozyme necessary for R2 RNA maturation. Although it cannot be completely ruled out, it seems unlikely that the degenerate elements replicate via reverse transcription, exploiting the R2Brfun element enzymatic machinery, but rather via genomic amplification of inserted 28S by unequal recombination. That inactive copies (both R2Brdeg or 5'-truncated elements) are not eliminated in a short term in stick insects contrasts with findings for the Drosophila R2, suggesting a widely different management of rDNA loci and a lower efficiency of the molecular drive while achieving the concerted evolution.
Garbaj, Aboubaker M.; Awad, Enas M.; Azwai, Salah M.; Abolghait, Said K.; Naas, Hesham T.; Moawad, Ashraf A.; Gammoudi, Fatim T.; Barbieri, Ilaria; Eldaghayes, Ibrahim M.
Aim: The aim of this work was to isolate and molecularly identify enterohemorrhagic Escherichia coli (EHEC) O157 in milk and dairy products in Libya, in addition; to clear the accuracy of cultural and biochemical identification as compared with molecular identification by partial sequencing of 16S rDNA for the existing isolates. Materials and Methods: A total of 108 samples of raw milk (cow, she-camel, and goat) and locally made dairy products (fermented cow’s milk, Maasora, Ricotta and ice cream) were collected from some regions (Janzour, Tripoli, Kremiya, Tajoura and Tobruk) in Libya. Samples were subjected to microbiological analysis for isolation of E. coli that was detected by conventional cultural and molecular method using polymerase chain reaction and partial sequencing of 16S rDNA. Results: Out of 108 samples, only 27 isolates were found to be EHEC O157 based on their cultural characteristics (Tellurite-Cefixime-Sorbitol MacConkey) that include 3 isolates from cow’s milk (11%), 3 isolates from she-camel’s milk (11%), two isolates from goat’s milk (7.4%) and 7 isolates from fermented raw milk samples (26%), isolates from fresh locally made soft cheeses (Maasora and Ricotta) were 9 (33%) and 3 (11%), respectively, while none of the ice cream samples revealed any growth. However, out of these 27 isolates, only 11 were confirmed to be E. coli by partial sequencing of 16S rDNA and E. coli O157 Latex agglutination test. Phylogenetic analysis revealed that majority of local E. coli isolates were related to E. coli O157:H7 FRIK944 strain. Conclusion: These results can be used for further studies on EHEC O157 as an emerging foodborne pathogen and its role in human infection in Libya. PMID:27956766
Zhang, Wen; Ki, Jang-Seu; Qian, Pei-Yuan
Bacteria, as the most abundant sediment organism, play a major role in the fate of pollutants. Therefore, many pollutant-related bacteria have been studied in harbor sediments, yet the entire bacterial profiles have not been reported. The bacterial diversity and community structures from sediments in Victoria Harbor (Hong Kong), including two polluted (VH and VHW) and two adjacent (open oceanic, TLC; estuary discharge affected, PC) sites, were characterized by analyses of four 16S rDNA clone libraries. Upon comparisons of RFLP patterns from 254 clones in the libraries, 178 unique phylotypes were retrieved. LIBSHUFF and Rarefaction analyses indicated that the sediment bacterial communities at the four sites showed high 16S rDNA richness and were significantly different from each other. Phylogenetic analysis of full-length 16S rDNA revealed 19 bacterial phyla in Victoria Harbor sediments. γ- and δ-proteobacteria, holophaga/acidobacteria, and planctomycetales were recorded in all the libraries. In addition, γ- and δ-proteobacteria were dominant at all sites (33.33-11.67%). Besides these two phyla, ɛ-proteobacteria, firmicutes, aminobacterium, holophaga/acidobacteria and bacteroidetes were judged to be major components of a given library since they constituted 10% or more of the total OTUs of the given library. The cyanobacteria, verrucomicrobia, β-proteobacteria, aminobacterium, chlorofiexi, and candidate division OP1, OP8 were detected in minor proportions in various libraries. A portion of the clones were only distantly related to sequences in the GenBank, suggesting bacteria in Victoria Harbor sediments were unique and diversified.
Tsuboi, Shun; Amemiya, Takashi; Seto, Koji; Itoh, Kiminori; Rajendran, Narasimmalu
Based on quantification and qualification of bacterial 16S rDNA, we verified the bacterial ecological characteristics of surface sediments of Lakes Shinji and Nakaumi, which are representative of coastal lagoons in Japan. Quantification and qualification of the 16S rDNA sequences was carried out using real time polymerase chain reaction and polymerase chain reaction denaturing gradient gel electrophoresis and non-metric multidimensional scaling, respectively. The results revealed that the copy number per gram of sediment ranged from 8.33 × 10(8) (Lake Nakaumi) to 1.69 × 10(11) (Honjo area), suggesting that bacterial carbon contributed only 0.05-9.64 % of the total carbon content in the samples. Compared with other aquatic environments, these results indicate that sedimentary bacteria are not likely to be important transporters of nutrients to higher trophic levels, or to act as carbon sinks in the lagoons. The bacterial compositions of Lake Shinji and Lake Nakaumi and the Honjo area were primarily influenced by sediment grain sizes and salinity, respectively. Statistical comparisons of the environmental properties suggested that the areas that were oxygen-abundant (Lake Shinji) and at a higher temperature (Honjo area) presented efficient organic matter degradation. The 16S rDNA copy number per gram of carbon and nitrogen showed the same tendency. Consequently, the primary roles of bacteria were degradation and preservation of organic materials, and this was affected by oxygen and temperature. These roles were supported by the bacterial diversity rather than the differences in the community compositions of the sedimentary bacteria in these coastal lagoons.
Background Hybridization is a useful strategy to alter the genotypes and phenotypes of the offspring. It could transfer the genome of one species to another through combing the different genome of parents in the hybrid offspring. And the offspring may exhibit advantages in growth rate, disease resistance, survival rate and appearance, which resulting from the combination of the beneficial traits from both parents. Results Diploid and triploid hybrids of female grass carp (Ctenopharyngodon idellus, GC, Cyprininae, 2n = 48) × male blunt snout bream (Megalobrama amblycephala, BSB, Cultrinae, 2n = 48) were successfully obtained by distant hybridization. Diploid hybrids had 48 chromosomes, with one set from GC and one set from BSB. Triploid hybrids possessed 72 chromosomes, with two sets from GC and one set from BSB. The morphological traits, growth rates, and feeding ecology of the parents and hybrid offspring were compared and analyzed. The two kinds of hybrid offspring exhibited significantly phenotypic divergence from GC and BSB. 2nGB hybrids showed similar growth rate compared to that of GC, and 3nGB hybrids significantly higher results. Furthermore, the feeding ecology of hybrid progeny was omnivorous. The 5S rDNA of GC, BSB and their hybrid offspring were also cloned and sequenced. There was only one type of 5S rDNA (designated type I: 180 bp) in GC and one type of 5S rDNA (designated type II: 188 bp) in BSB. However, in the hybrid progeny, diploid and triploid hybrids both inherited type I and type II from their parents, respectively. In addition, a chimera of type I and type II was observed in the genome of diploid and triploid hybrids, excepting a 10 bp of polyA insertion in type II sequence of the chimera of the diploid hybrids. Conclusions This is the first report of diploid and triploid hybrids being produced by crossing GC and BSB, which have the same chromosome number. The obtainment of two new hybrid offspring has significance in fish
Kokuzawa, Takuya; Ichikawa-Seki, Madoka; Itagaki, Tadashi
We analyzed almost complete 18S rDNA sequences of 10 bovine Eimeria species, namely Eimeria alabamensis, E. auburnensis, E. bovis, E. bukidnonensis, E. canadensis, E. cylindrica, E. ellipsoidalis, E. subspherica, E. wyomingensis and E. zuernii. Although these sequences showed intraspecific variation in 8 species, the sequences of each species were clustered in monophyletic groups in all species, except E. auburnensis. The sequences constituted 3 distinct clusters in a phylogenetic tree with relatively high bootstrap values; however, the members including each cluster shared no similarities in oocyst morphology.
Hayashi, K; Tazumi, A; Nakanishi, S; Nakajima, T; Matsubara, K; Ueno, H; Moore, J E; Millar, B C; Matsuda, M
Following PCR amplification and sequencing, nucleotide sequence alignment analyses demonstrated the presence of two kinds of 16S-23S rDNA internal spacer regions (ISRs), namely, long length ISRs of 837-844 base pair (bp) [n = six for urease-negative (UN) Campylobacter lari isolates, UN C. lari JCM2530(T), RM2100, 176, 293, 299 and 448] and short length ISRs of 679-725 bp [n = six for UN C. lari: n = 14 for urease-positive thermophilic Campylobacter (UPTC) isolates]. The analyses also indicated that the short length ISRs mainly lacked the 156 bp sequence from the nucleotide positions 122-277 bp in long length ISRs for UN C. lari JCM2530(T). The 156 bp sequences shared 94.9-96.8 % sequence similarity among six isolates. Surprisingly, atypical tRNA(Ala) gene segment (5' end 35 bp), which was extremely truncated, occurred within the 156 bp sequences in the long length ISRs, as an unexpected tRNA(Ala) pseudogene. An order of the intercistronic tRNA genes within the short nucleotide spacer of 5'-16S rDNA-tRNA(Ala)-tRNA(Ile)-23S rDNA-3' occurred in all the C. lari isolates examined.
Takishita, Kiyotaka; Miyake, Hiroshi; Kawato, Masaru; Maruyama, Tadashi
Recent culture-independent molecular analyses have shown the diversity and ecological importance of microbial eukaryotes (protists) in various marine environments. In the present study we directly extracted DNA from anoxic sediment near active fumaroles on a submarine caldera floor at a depth of 200 m and constructed genetic libraries of PCR-amplified eukaryotic small-subunit (SSU) rDNA. By sequencing cloned SSU rDNA of the libraries and their phylogenetic analyses, it was shown that most sequences have affiliations with known major lineages of eukaryotes (Cercozoa, Alveolata, stramenopiles and Opisthokonta). In particular, some sequences were closely related to those of representatives of eukaryotic parasites, such as Phagomyxa and Cryothecomonas of Cercozoa, Pirsonia of stramenopiles and Ichthyosporea of Opisthokonta, although it is not clear whether the organisms occur in free-living or parasitic forms. In addition, other sequences did not seem to be related to any described eukaryotic lineages suggesting the existence of novel eukaryotes at a high-taxonomic level in the sediment. The community composition of microbial eukaryotes in the sediment we surveyed was different overall from those of other anoxic marine environments previously investigated.
Sasaki, Y; Yamamoto, K; Amimoto, K; Kojima, A; Ogikubo, Y; Norimatsu, M; Ogata, H; Tamura, Y
Amplification of the 16S-23S rDNA spacer region by polymerase chain reaction (PCR) was used for the rapid detection of Clostridium chauvoei and C septicum. To assess its specificity, PCR was performed with total DNA from 42 strains of clostridia and three strains of other genera. PCR products specific to C chauvoei or to C septicum were generated from homologous cultures only. Clostridium chauvoer-specific or C septicum-specific amplicons were also generated from tissues of cows experimentally infected with C chauvoei or C septicum and in DNA samples from cows clinically diagnosed as having blackleg or malignant oedema. These results suggest that a species-specific PCR may be useful for the rapid and direct detection of C chauvoei and C septicum in clinical specimens.
This book discusses the following topics: PLANTS: PLANT DNA: Contents and Systematics. Repeated DNA Sequences and Polyploidy in Cereal Crops. Homology of Nonrepeated DNA Sequences in Phylogeny of Fungal Species. Chloropast DNA and Phylogenetic Relationships. rDNA: Evolution Over a Billion Years. 23S rRNA-derived Small Ribosomal RNAs: Their Structure and Evolution with Reference to Plant Phylogeny. Molecular Analysis of Plant DNA Genomes: Conserved and Diverged DNA Sequences. A Critical Review of Some Terminologies Used for Additional DNA in Plant Chromosomes and Index.
Background The genus Arachis comprises 80 species and it is subdivided into nine taxonomic sections (Arachis, Caulorrhizae, Erectoides, Extranervosae, Heteranthae, Procumbentes, Rhizomatosae, Trierectoides, and Triseminatae). This genus is naturally confined to South America and most of its species are native to Brazil. In order to provide a better understanding of the evolution of the genus, we reconstructed the phylogeny of 45 species using the variation observed on nucleotide sequences in internal transcribed spacer regions (ITS1 and ITS2) and 5.8 S of nuclear ribosomal DNA. Results Intraspecific variation was detected, but in general it was not enough to place accessions of the same species in different clades. Our data support the view that Arachis is a monophyletic group and suggested Heteranthae as the most primitive section of genus Arachis. The results confirmed the circumscriptions of some sections (Caulorrhizae, Extranervosae), but raised questions about others. Sections Erectoides, Trierectoides and Procumbentes were not well defined, while sections Arachis and Rhizomatosae seem to include species that could be moved to different sections. The division of section Arachis into A and B genome species was also observed in the phylogenetic tree and these two groups of species may not have a monophyletic origin. The 2n = 2x = 18 species of section Arachis (A. praecox, A. palustris and A. decora) were all placed in the same clade, indicating they are closely related to each other, and their genomes are more related to B genome than to the A genome. Data also allowed insights on the origin of tetraploid A. glabrata, suggesting rhizome appeared twice within the genus and raising questions about the placement of that species in section Rhizomatosae. Conclusion The main clades established in this study in general agreed with many other studies that have used other types of evidences and sets of species, being some of them included in our study and some not. Thus
Feng, Shangguo; Jiang, Mengying; Shi, Yujun; Jiao, Kaili; Shen, Chenjia; Lu, Jiangjie; Ying, Qicai; Wang, Huizhong
Recently, commercial interest in Physalis species has grown worldwide due to their high nutritional value, edible fruit, and potential medicinal properties. However, many Physalis species have similar shapes and are easily confused, and consequently the phylogenetic relationships between Physalis species are poorly understood. This hinders their safe utilization and genetic resource conservation. In this study, the nuclear ribosomal ITS2 region was used to identify species and phylogenetically examine Physalis. Eighty-six ITS2 regions from 45 Physalis species were analyzed. The ITS2 sequences were aligned using Clustal W and genetic distances were calculated using MEGA V6.0. The results showed that ITS2 regions have significant intra- and inter-specific divergences, obvious barcoding gaps, and higher species discrimination rates (82.2% for both the BLASTA1 and nearest distance methods). In addition, the secondary structure of ITS2 provided another way to differentiate species. Cluster analysis based on ITS2 regions largely concurred with the relationships among Physalis species established by many previous molecular analyses, and showed that most sections of Physalis appear to be polyphyletic. Our results demonstrated that ITS2 can be used as an efficient and powerful marker in the identification and phylogenetic study of Physalis species. The technique provides a scientific basis for the conservation of Physalis plants and for utilization of resources.
Feng, Shangguo; Jiang, Mengying; Shi, Yujun; Jiao, Kaili; Shen, Chenjia; Lu, Jiangjie; Ying, Qicai; Wang, Huizhong
Recently, commercial interest in Physalis species has grown worldwide due to their high nutritional value, edible fruit, and potential medicinal properties. However, many Physalis species have similar shapes and are easily confused, and consequently the phylogenetic relationships between Physalis species are poorly understood. This hinders their safe utilization and genetic resource conservation. In this study, the nuclear ribosomal ITS2 region was used to identify species and phylogenetically examine Physalis. Eighty-six ITS2 regions from 45 Physalis species were analyzed. The ITS2 sequences were aligned using Clustal W and genetic distances were calculated using MEGA V6.0. The results showed that ITS2 regions have significant intra- and inter-specific divergences, obvious barcoding gaps, and higher species discrimination rates (82.2% for both the BLASTA1 and nearest distance methods). In addition, the secondary structure of ITS2 provided another way to differentiate species. Cluster analysis based on ITS2 regions largely concurred with the relationships among Physalis species established by many previous molecular analyses, and showed that most sections of Physalis appear to be polyphyletic. Our results demonstrated that ITS2 can be used as an efficient and powerful marker in the identification and phylogenetic study of Physalis species. The technique provides a scientific basis for the conservation of Physalis plants and for utilization of resources. PMID:27486467
Knoll, Alexander; Puchta, Holger
The stability of repetitive sequences in complex eukaryotic genomes is safeguarded by factors suppressing homologues recombination. Prominent in this is the role of the RTR complex. In plants, it consists of the RecQ helicase RECQ4A, the topoisomerase TOP3α and RMI1. Like mammals, but not yeast, plants harbor an additional complex partner, RMI2. Here, we demonstrate that, in Arabidopsis thaliana, RMI2 is involved in the repair of aberrant replication intermediates in root meristems as well as in intrastrand crosslink repair. In both instances, RMI2 is involved independently of the DNA helicase RTEL1. Surprisingly, simultaneous loss of RMI2 and RTEL1 leads to loss of male fertility. As both the RTR complex and RTEL1 are involved in suppression of homologous recombination (HR), we tested the efficiency of HR in the double mutant rmi2-2 rtel1-1 and found a synergistic enhancement (80-fold). Searching for natural target sequences we found that RTEL1 is required for stabilizing 45S rDNA repeats. In the double mutant with rmi2-2 the number of 45S rDNA repeats is further decreased sustaining independent roles of both factors in this process. Thus, loss of suppression of HR does not only lead to a destabilization of rDNA repeats but might be especially deleterious for tissues undergoing multiple cell divisions such as the male germline. PMID:27760121
Delgado, Susana; Suárez, Adolfo; Mayo, Baltasar
The aim of this work was to examine by culturing the changes in the total and indicator populations of the feces of two individuals over 1 year and to identify the dominant microbial components of a single sample of feces from each donor. Populations and dominant bacteria from a sample of colonic mucosa from a further individual were also assessed. The culture results were then compared to those obtained with the same samples by 16S rDNA cloning and sequencing. High interindividual variation in representative microbial populations of the gastrointestinal tract (GIT) was revealed by both the culture and the culture-independent techniques. Species belonging to Clostridium clusters (XIVa, IV, and XVIII) predominated in both the fecal and the mucosal samples (except in the mucose cultured isolates), members of Clostridium coccoides cluster XIVa being the most numerous microorganisms. Species of gamma-proteobacteria (Escherichia coli and Shigella spp.), bifidobacteria, and actinobacteria appeared in lower numbers than those of clostridia. From the mucosal cultured sample, only facultative anaerobes and bifidobacteria were recovered, suggesting destruction of the anaerobe population during processing. In accordance with this, the microbial diversity revealed by 16S rDNA sequence analysis was greater than that revealed by culturing. Despite large interindividual differences, distinct human communities may have group-associated GIT microbiota characteristics, such as the low number of Bacteroides seen in the subjects in this study.
Viola, L B; Almeida, R S; Ferreira, R C; Campaner, M; Takata, C S A; Rodrigues, A C; Paiva, F; Camargo, E P; Teixeira, M M G
In this study, using a combined data set of SSU rDNA and gGAPDH gene sequences, we provide phylogenetic evidence that supports clustering of crocodilian trypanosomes from the Brazilian Caiman yacare (Alligatoridae) and Trypanosoma grayi, a species that circulates between African crocodiles (Crocodilydae) and tsetse flies. In a survey of trypanosomes in Caiman yacare from the Brazilian Pantanal, the prevalence of trypanosome infection was 35% as determined by microhaematocrit and haemoculture, and 9 cultures were obtained. The morphology of trypomastigotes from caiman blood and tissue imprints was compared with those described for other crocodilian trypanosomes. Differences in morphology and growth behaviour of caiman trypanosomes were corroborated by molecular polymorphism that revealed 2 genotypes. Eight isolates were ascribed to genotype Cay01 and 1 to genotype Cay02. Phylogenetic inferences based on concatenated SSU rDNA and gGAPDH sequences showed that caiman isolates are closely related to T. grayi, constituting a well-supported monophyletic assemblage (clade T. grayi). Divergence time estimates based on clade composition, and biogeographical and geological events were used to discuss the relationships between the evolutionary histories of crocodilian trypanosomes and their hosts.
Siragusa, Alex J; Swenson, Janice E; Casamatta, Dale A
The culturable microbial community within the pitcher fluid of 93 Sarracenia minor carnivorous plants was examined over a 2-year study. Many aspects of the plant/bacterial/insect interaction within the pitcher fluid are minimally understood because the bacterial taxa present in these pitchers have not been identified. Thirteen isolates were characterized by 16S rDNA sequencing and subsequent phylogenetic analysis. The Proteobacteria were the most abundant taxa and included representatives from Serratia, Achromobacter, and Pantoea. The Actinobacteria Micrococcus was also abundant while Bacillus, Lactococcus, Chryseobacterium, and Rhodococcus were infrequently encountered. Several isolates conformed to species identifiers (>98% rDNA gene sequence similarity) including Serratia marcescens (isolates found in 27.5% of pitchers), Achromobacter xylosoxidans (37.6%), Micrococcus luteus (40.9%), Bacillus cereus (isolates found in 10.2%), Bacillus thuringiensis (5.4%), Lactococcus lactis (17.2%), and Rhodococcus equi (2.2%). Species-area curves suggest that sampling efforts were sufficient to recover a representative culturable bacterial community. The bacteria present represent a diverse community probably as a result of introduction by insect vectors, but the ecological significance remains under explored.
Mandakovic, Dinka; Glasner, Benjamín; Maldonado, Jonathan; Aravena, Pamela; González, Mauricio; Cambiazo, Verónica; Pulgar, Rodrigo
The gram negative facultative bacterium P. salmonis is the etiological agent of Salmonid Rickettsial Septicaemia (SRS), a severe disease that causes important economic losses in the global salmon farmer industry. Despite efforts to control this disease, the high frequency of new epizootic events indicate that the vaccine and antibiotics treatments have limited effectiveness, therefore the preventive and diagnostic approaches must be improved. A comparison of several methodologies for SRS diagnostic indicate differences in their specificity and its capacity to detect other bacteria coexisting with P. salmonis in culture media (contamination) and fish samples (coinfection), aspects relevant for research, vaccine development and clinical diagnostic. By computer-simulation analyses, we identified a group of restriction enzymes that generate unique P. salmonis 16S rDNA band patterns, distinguishable from all other bacteria. From this information, we designed and developed a PCR-RFLP (Polymerase Chain Reaction—Restriction Fragment Length Polymorphism) assay, which was validated using 16S rDNA universal primers and restriction enzyme PmaCI for the amplification and digestion, respectively. Experimental validation was performed by comparing the restriction pattern of P. salmonis with the restriction patterns generated by bacteria that cohabit with P. salmonis (fish bacterial isolates and culture media contaminants). Our results indicate that the restriction enzyme selection pipeline was suitable to design a more specific, sensible, faster and cheaper assay than the currently used P. salmonis detection methodologies. PMID:27242682
John, Uwe; Litaker, R. Wayne; Montresor, Marina; Murray, Shauna; Brosnahan, Michael L.; Anderson, Donald M.
The Alexandrium tamarense species complex is one of the most studied marine dinoflagellate groups due to its ecological, toxicological and economic importance. Several members of this complex produce saxitoxin and its congeners – potent neurotoxins that cause paralytic shellfish poisoning. Isolates from this complex are assigned to A. tamarense, A. fundyense, or A. catenella based on two main morphological characters: the ability to form chains and the presence/absence of a ventral pore between Plates 1′ and 4′. However, studies have shown that these characters are not consistent and/or distinctive. Further, phylogenies based on multiple regions in the rDNA operon indicate that the sequences from morphologically indistinguishable isolates partition into five clades. These clades were initially named based on their presumed geographic distribution, but recently were renamed as Groups I–V following the discovery of sympatry among some groups. In this study we present data on morphology, ITS/5.8S genetic distances, ITS2 compensatory base changes, mating incompatibilities, toxicity, the sxtA toxin synthesis gene, and rDNA phylogenies. All results were consistent with each group representing a distinct cryptic species. Accordingly, the groups were assigned species names as follows: Group I, A. fundyense; Group II, A. mediterraneum; Group III, A. tamarense; Group IV, A. pacificum; Group V, A. australiense. PMID:25460230
Fang, J.; Arakawa, S.; Kato, C.; Schouten, S.
Microbial communities in Calyptogena sediment and microbial mats of Sagami Bay, Japan were characterized by using 16S rDNA sequencing and lipid biomarker analysis. Characterization of 16S rDNA isolated from these samples suggested a predominance of bacterial phylotypes related to γ- (57-64%) and δ-subclasses (27-29%) of the Proteobacteria. The ɛ-subclass of the Proteobacteria commonly found in cold seeps and hydrothermal vents were only detected in the microbial mat sample. There are significantly different archaeal phylotypes between Calyptogena sediment and microbial mat; the former contains only Crenarchaeota clones (100% of the total archaeal clones) and the latter exclusively Euryarchaeota clones including the ANME-2a and ANME-2c archaeal groups. Many of these lineages are as yet uncultured and undescribed groups of bacteria and archaea. Phospholipid fatty acid analysis suggests the presence of sulfate-reducing and sulfur-oxidizing bacteria. Results of intact glyceryl dialkyl glyceryl tetraether (GDGT) lipid analysis indicate the presence of nonthermophilic marine planktonic archaea. These results suggest that the microbial community in the Sagami Bay seep site is distinct from previously characterized cold seep environments.
Landaburu, Fernanda; Cuestas, María Luján; Rubio, Andrea; Elías, Nahuel Alejandro; Daneri, Gabriela Lopez; Veciño, Cecilia; Iovannitti, Cristina A; Mujica, María Teresa
The internal transcribed spacer (ITS) regions of rDNA genes of 49 Histoplasma capsulatum (48 from clinical samples and one from soil) isolates were examined. Nucleotide sequence heterogeneity within this region was useful for phylogenetic classification of H. capsulatum and species identification. Thus, in 45 of 49 isolates we observed higher percentages of identity in the nucleotide sequences of ITS regions when the isolates studied herein were compared with those reported in our country in the South America B clade. Phylogenetic analyses of rDNA sequences corresponding to the 537 bp of the ITS region obtained from H. capsulatum isolates assigned South America type B clade (45 isolates), North America type 1 and Asia clade (2 isolates each one). H. capsulatum strains isolated from soil and from patients living in Argentina (45 of 49) clustered together with the H. capsulatum isolates of the South America B clade. The high level of genetic similarity among our isolates suggests that almost one genetic population is present in the microenvironment. Isolates described as H. capsulatum var. capsulatum or var. farciminosum (2 isolates) did not form a monophyletic group and were found in the Asia clade. Subsequent studies are needed to properly identify these isolates.
El Sheikha, Aly Farag; Condur, Ana; Métayer, Isabelle; Nguyen, Doan Duy Le; Loiseau, Gérard; Montet, Didier
The determination of geographical origin is a demand of the traceability system of import-export food products. One hypothesis for tracing the source of a product is by global analysis of the microbial communities of the food and statistical linkage of this analysis to the geographical origin of the food. For this purpose, a molecular technique employing 26S rDNA profiles generated by PCR-DGGE was used to detect the variation in yeast community structures of three species of Physalis fruit (Physalis ixocarpa Brat, Physalis pubescens L, Physalis pruinosa L) from four Egyptian regions (Qalyoubia, Minufiya, Beheira and Alexandria Governments). When the 26S rDNA profiles were analysed by multivariate analysis, distinct microbial communities were detected. The band profiles of Physalis yeasts from different Governments were specific for each location and could be used as a bar code to discriminate the origin of the fruits. This method is a new traceability tool which provides fruit products with a unique biological bar code and makes it possible to trace back the fruits to their original location.
Guo, Yadong; Cai, Jifeng; Chang, Yunfeng; Li, Xiang; Liu, Qinlai; Wang, Xinghua; Wang, Xiang; Zhong, Ming; Wen, Jifang; Wang, Jiangfeng
Insects attracted to cadavers may provide important indications of the postmortem interval (PMI). However, use of the flesh flies (Diptera: Sarcophagidae) for PMI estimation is limited as the species are often not morphologically distinct, especially as immatures. In this study, 23 forensically important flesh flies were collected from 13 locations in 10 Chinese provinces. Then, a 278-bp segment of the cytochrome oxidase subunits one (COI) gene and a 289-bp segment of the 16S rDNA gene of all specimens were successfully sequenced. Phylogenetic analysis of the sequenced segments showed that all sarcophagid specimens were properly assigned into four species (Boerttcherisca peregrina [Robineau-Desvoidy, 1830], Helicophagella melanura [Meigen, 1826], Parasarcophaga albiceps [Meigen, 1826], and Parasarcophaga dux [Thompson, 1869]) with relatively strong supporting values, thus indicating that the COI and 16S rDNA regions are suitable for identification of sarcophagid species. The difference between intraspecific threshold and interspecific divergence confirmed the potential of the two regions for sarcophagid species identification.
Lim, K Y; Skalicka, K; Koukalova, B; Volkov, R A; Matyasek, R; Hemleben, V; Leitch, A R; Kovarik, A
An approximately 135-bp sequence called the A1/A2 repeat was isolated from the transcribed region of the 26-18S rDNA intergenic spacer (IGS) of Nicotiana tomentosiformis. Fluorescence in situ hybridization (FISH) and Southern blot analysis revealed its occurrence as an independent satellite (termed an A1/A2 satellite) outside of rDNA loci in species of Nicotiana section Tomentosae. The chromosomal location, patterns of genomic dispersion, and copy numbers of its tandemly arranged units varied between the species. In more distantly related Nicotiana species the A1/A2 repeats were found only at the nucleolar organizer regions (NOR). There was a trend toward the elimination of the A1/A2 satellite in N. tabacum (tobacco), an allotetraploid with parents closely related to the diploids N. sylvestris and N. tomentosiformis. This process may have already commenced in an S(3) generation of synthetic tobacco. Cytosine residues in the IGS were significantly hypomethylated compared with the A1/A2 satellite. There was no clear separation between the IGS and satellite fractions in sequence analysis of individual clones and we found no evidence for CG suppression. Taken together the data indicate a dynamic nature of the A1/A2 repeats in Nicotiana genomes, with evidence for recurrent integration, copy number expansions, and contractions. PMID:15126410
Mandakovic, Dinka; Glasner, Benjamín; Maldonado, Jonathan; Aravena, Pamela; González, Mauricio; Cambiazo, Verónica; Pulgar, Rodrigo
The gram negative facultative bacterium P. salmonis is the etiological agent of Salmonid Rickettsial Septicaemia (SRS), a severe disease that causes important economic losses in the global salmon farmer industry. Despite efforts to control this disease, the high frequency of new epizootic events indicate that the vaccine and antibiotics treatments have limited effectiveness, therefore the preventive and diagnostic approaches must be improved. A comparison of several methodologies for SRS diagnostic indicate differences in their specificity and its capacity to detect other bacteria coexisting with P. salmonis in culture media (contamination) and fish samples (coinfection), aspects relevant for research, vaccine development and clinical diagnostic. By computer-simulation analyses, we identified a group of restriction enzymes that generate unique P. salmonis 16S rDNA band patterns, distinguishable from all other bacteria. From this information, we designed and developed a PCR-RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism) assay, which was validated using 16S rDNA universal primers and restriction enzyme PmaCI for the amplification and digestion, respectively. Experimental validation was performed by comparing the restriction pattern of P. salmonis with the restriction patterns generated by bacteria that cohabit with P. salmonis (fish bacterial isolates and culture media contaminants). Our results indicate that the restriction enzyme selection pipeline was suitable to design a more specific, sensible, faster and cheaper assay than the currently used P. salmonis detection methodologies.
Waite, Joy G; Jones, Joseph M; Yousef, Ahmed E
Investigating microbial spoilage of food is hampered by the lack of suitable growth media and protocols to characterize the causative agents. Microbial spoilage of salad dressing is sporadic and relatively unpredictable, thus processors struggle to develop strategies to minimize or prevent spoilage of this product. The objectives of this study were to (i) induce and characterize spoilage events in ranch-style dressing as a model food, and (ii) isolate and identify the causative microorganisms using traditional and food-based media, coupled with rDNA sequence analysis. Ranch dressing (pH 4.4) was prepared and stored at 25 degrees C for 14 d and microbial populations were recovered on MRS agar and ranch dressing agar (RDA), a newly formulated food-based medium. When isolates suspected as the spoilage agents were inoculated into ranch dressing and held at 25 degrees C for 9-10 d, three unique spoilage events were characterized. Using rDNA sequence comparisons, spoilage organisms were identified as Lactobacillus brevis, Pediococcus acidilactici, and Torulaspora delbrueckii. P. acidilactici produced flat-sour spoilage, whereas Lb. brevis resulted in product acidification and moderate gas production. The RDA medium allowed for optimum recovery of the excessive gas-producing spoilage yeast, T. delbrueckii. The isolation and identification strategy utilized in this work should assist in the characterization of spoilage organisms in other food systems.
Boeger, W A; Kritsky, D C; Domingues, M V; Bueno-Silva, M
Phylogenetic analyses of partial sequences of 18S and 28S rDNA of some monogenoids, including monocotylids and a specimen of Loimosina sp. collected from a hammerhead shark off Brazil, indicated that the Loimoidae (as represented by the specimen of Loimosina sp.) represents an in-group taxon of the Monocotylidae. In all analyses, the Loimoidae fell within a major monocotylid clade including species of the Heterocotylinae, Decacotylinae, and Monocotylinae. The Loimoidae formed a terminal clade with two heterocotyline species, Troglocephalus rhinobatidis and Neoheterocotyle rhinobatis, for which it represented the sister taxon. The following morphological characters supported the clade comprising the Loimoidae, Heterocotylinae, Decacotylinae and Monocotylinae: single vagina present, presence of a narrow deep anchor root, and presence of a marginal haptoral membrane. The presence of cephalic pits was identified as a putative synapomorphy for the clade (Loimoidae (T. rhinobatidis, N. rhinobatis)). Although rDNA sequence data support the rejection of the Loimoidae and incorporating its species into the Monocotylidae, this action was not recommended pending a full phylogenetic analysis of morphological data.
Singh, Shalini Thakur; Priya, Natarajan Gayatri; Kumar, Jitendra; Rana, Vipin Singh; Ellango, R; Joshi, Adita; Priyadarshini, Garima; Asokan, R; Rajagopal, Raman
Bemisia tabaci is the major vector pest of agricultural crops all over the world. In this study we report the different bacterial endosymbionts associated with B. tabaci sampled from 14 different locations in North India. Using 16S rDNA clone library sequences we were able to identify Portiera, the primary endosymbiont of B. tabaci, and other secondary endosymbionts like Cardinium, Wolbachia, Rickettsia and Arsenophonus. Along with these we also detected Bacillus, Enterobacter, Paracoccus and Acinetobacter. These secondary endosymbionts were not uniformly distributed in all the locations. Phylogenetic analysis of 16S rDNA sequences of Cardinium, Wolbachia, Rickettsia and Arsenophonus showed that each of these bacteria form a separate cluster when compared to their respective counterparts from other parts of the world. MtCO1 gene based phylogenetic analysis showed the presence of Asia I and Asia II genetic groups of B. tabaci in N. India. The multiple correspondence analyses showed no correlation between the host genetic group and the endosymbiont diversity. These results suggest that the bacterial endosymbiont diversity of B. tabaci is much larger and complex than previously perceived and probably N. Indian strains of the bacterial symbionts could have evolved from some other ancestor.
DNA helicases are enzymes that use the chemical energy to separate DNA duplex into their single-stranded forms. The ribosome, which catalyzes the translation of messenger RNAs (mRNAs) into proteins, can also unwind mRNA duplex. According to their structures, the DNA helicases can fall broadly into hexameric and monomeric forms. A puzzling issue for the monomeric helicases is that although they have similar structures, in vitro biochemical data showed convincingly that in the monomeric forms some have very weak DNA unwinding activities, some have relatively high unwinding activities while others have high unwinding activities. However, in the dimeric or oligomeric forms all of them have high unwinding activities. In addition, in the monomeric forms all of them can translocate efficiently along the single-stranded DNA (ssDNA). Here, we propose a model of the translocation along the ssDNA and DNA unwinding by the monomeric helicases, providing a consistent explanation of these in vitro experimental data. Moreover, by comparing the present model for the monomeric helicases with the model for the hexameric helicases and that for the ribosome which were proposed before, a unified model of nucleic acid unwinding by the three enzymes is proposed.
Adams, Gerard C; Surve-Iyer, Rupa S; Iezzoni, Amy F
Leucostoma species that are the causal agents of Cytospora canker of stone and pome fruit trees were studied in detail. DNA sequence of the internal transcribed spacer regions and the 5.8S of the nuclear ribosomal DNA operon (ITS rDNA) supplied sufficient characters to assess the phylogenetic relationships among species of Leucostoma, Valsa, Valsella, and related anamorphs in Cytospora. Parsimony analysis of the aligned sequence divided Cytospora isolates from fruit trees into clades that generally agreed with the morphological species concepts, and with some of the phenetic groupings (PG 1-6) identified previously by isozyme analysis and cultural characteristics. Phylogenetic analysis inferred that isolates of L. persoonii formed two well-resolved clades distinct from isolates of L. cinctum. Phylogenetic analysis of the ITS rDNA, isozyme analysis, and cultural characteristics supported the inference that L. persoonii groups PG 2 and PG 3 were populations of a new species apparently more genetically different from L. persoonii PG 1 than from isolates representative of L. massariana, L. niveum, L. translucens, and Valsella melastoma. The new species, L. parapersoonii, was described. A diverse collection of isolates of L. cinctum, L. persoonii, and L. parapersoonii were examined for genetic variation using restriction fragment length polymorphism (RFLP) analysis of the ITS rDNA and the five prime end of the large subunit of the rDNA (LSU rDNA). HinfI and HpaII endonucleases were each useful in dividing the Leucostoma isolates into RFLP profiles corresponding to the isozyme phenetic groups, PG 1-6. RFLP analysis was more effective than isozyme analysis in uncovering variation among isolates of L. persoonii PG 1, but less effective within L. cinctum populations. Isolates representative of seven of the L. persoonii formae speciales proposed by G. Défago in 1935 were found to be genetically diverse isolates of PG 1. Two large insertions, 415 and 309 nucleotides long, in
Cutillas, C; Oliveros, R; de Rojas, M; Guevara, D C
Trichuris muris has been isolated from murid hosts ( Apodemus sylvaticus and Mus musculus) and Trichuris arvicolae from arvicolid rodents in Barcelona, Spain. Genomic DNA was isolated and the ITS1-5.8S-ITS2 segment from the ribosomal DNA (rDNA) was amplified and sequenced using polymerase chain reaction techniques. The ITS2 of both populations isolated from Apodemus and Mus was 382 nucleotides in length and had a GC content of about 60.73%, while the ITS2 of T. arvicolae was 442 nucleotides in length and had a GC content of about 59.8%. Furthermore, the ITS1 of Trichuris from murids was 448 nucleotides in length and had a GC content of about 56.47%, while T. arvicolae was 446 nucleotides in length and had 57.62% of GC content. A total of 161 and 173 nucleotides were observed along the 5.8S gene of T. murisand T. arvicolae, respectively; This difference in nucleotides was due to the insertion of a DNA segment (transposon) in the 5.8S sequence of the latter species. Slight intraindividual and intraspecific variations were detected in the rDNA of both species. The presence of microsatellites was observed in all of the individuals assayed. Sequence analysis of the internal transcribed spacers and the 5.8S gene demonstrated no sequence differences between T. muris isolated from both of its murid hosts. Nevertheless, clear differences were detected between the ITS2, ITS1 and 5.8S gene of T. muris and T. arvicolae. This corroborates the existence of two separate Trichuris species in murid and arvicolid hosts. Furthermore, a phylogenetic analysis was carried out and endonucleases restriction maps were elaborated for both species.
Xu, Wei; Luo, Zhu-Hua; Guo, Shuangshuang; Pang, Ka-Lai
We investigated the diversity of fungal communities in 6 different deep-sea sediment samples of the Pacific Ocean based on three different types of clone libraries, including internal transcribed spacer (ITS), 18S rDNA, and 28S rDNA regions. A total of 1978 clones were generated from 18 environmental clone libraries, resulting in 140 fungal operational taxonomic units (OTUs), including 18 OTUs from ITS, 44 OTUs from 18S rDNA, and 78 OTUs from 28S rDNA gene primer sets. The majority of the recovered sequences belonged to diverse phylotypes of the Ascomycota and Basidiomycota. Additionally, our study revealed a total of 46 novel fungal phylotypes, which showed low similarities (<97%) with available fungal sequences in the GenBank, including a novel Zygomycete lineage, suggesting possible new fungal taxa occurring in the deep-sea sediments. The results suggested that 28S rDNA is an efficient target gene to describe fungal community in deep-sea environment.
Zhang, D J; Yuan, W T; Li, M T; Zhang, Y H
Rhodiola plants are a valuable resource in traditional Chinese medicine. The objective of this study was to evaluate the correlation between ribosomal DNA internal transcribed spacer (ITS) sequences and the three active components in Rhodiola plants. For this, we determined ITS sequence polymorphisms and the concentrations of active components salidroside, tyrosol, and gallic acid in different Rhodiola species from the Tibetan Plateau. In a total of 23 Rhodiola samples, 16 different haplotypes were defined based on their ITS sequences. Analysis of the active components in these same samples revealed that salidroside was not detected in species with haplotypes H4, H5, or H10, tyrosol was not detected with haplotypes H3, H5, H7, H10, H14, or H15, and gallic acid was detected in with all haplotypes except H14 and H15. In addition, the concentrations of salidroside, tyrosol and gallic acid varied between samples with different haplotypes as well as those with the same haplotype, implying that no significant correlation exists between haplotype and salidroside, tyrosol or gallic acid concentrations. However, a statistically significant positive correlation was observed for among these three active components.
Bernier, L; Hamelin, R C; Ouellette, G B
The small subunit (SSU) and the internal transcribed spacer (ITS) of nuclear ribosomal DNA genes from 27 specimens of the fungal genera Gremmeniella and Ascocalyx were amplified by PCR. Length polymorphisms were observed in the SSU and allowed the differentiation of four groups among the isolates tested: (i) Ascocalyx abietis; (ii) Gremmeniella isolates from Picea spp.; (iii) Gremmeniella isolates from Abies balsamea; and (iv) Gremmeniella isolates from Abies sacchalinensis, Larix spp., and Pinus spp. The amplified ITS was the same length for all Gremmeniella specimens and was 60 bp longer in A. abietis. Phylogenetic analysis of length polymorphisms and of 24 restriction sites in the SSU and ITS showed that Gremmeniella isolates were more related to each other than to the Ascocalyx isolate. Furthermore, seven groups were evident within the genus Gremmeniella. Our results confirm that Gremmeniella and Ascocalyx should be kept as different taxa and suggest that the taxonomy of the former could be revised to consider isolates from Abies balsamea and from Picea spp. to be two different varieties while incorporating Gremmeniella laricina into G. abietina, as a new variety. Images PMID:7912501
Takamiya, Tomoko; Wongsawad, Pheravut; Tajima, Natsuko; Shioda, Nao; Lu, Jun Feng; Wen, Chi Luan; Wu, Jin Bin; Handa, Takashi; Iijima, Hiroshi; Kitanaka, Susumu; Yukawa, Tomohisa
Stems of genus Dendrobium (Orchidaceae) have been traditionally used as an herbal medicine (Dendrobii Herba) in Eastern Asia. Although demand for Dendrobium is increasing rapidly, wild resources are decreasing due to over-collection. This study aimed to identify plant sources of Dendrobii Herba on the market based on sequences of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA. We constructed an ITS1-5.8S-ITS2 sequence database of 196 Dendrobium species, and the database was employed to identify 21 herbal samples. We found that 13 Dendrobium species (D. catenatum, D. cucullatum, D. denudans, D. devonianum, D. eriiflorum, D. hancockii, D. linawianum, D. lituiflorum, D. loddigesii, D. polyanthum, D. primulinum, D. regium, and D. transparens) were possibly used as plant sources of Dendrobii Herba, and unidentified species allied to D. denudans, D. eriiflorum, D. gregulus, or D. hemimelanoglossum were also used as sources. Furthermore, it is clear that D. catenatum is one of the most important sources of Dendrobii Herba (5 out of 21 samples).
Kuick, R.; Asakawa, J. I.; Neel, J. V.; Kodaira, M.; Satoh, C.; Thoraval, D.; Gonzalez, I. L.; Hanash, S. M.
We have investigated the variation in human ribosomal DNA repeat units as revealed in two-dimensional electrophoretic separations of genomic restriction fragments that were end-labeled at NotI cleavage sites. The transcribed portion of the ribosomal DNA results in ~20 labeled fragments visible on each gel as multicopy spots. We have mapped these spots to the sequences responsible for their appearance on the gels, based on their migration positions and direct sequencing of spots, and describe several previously unreported sources of variation. By studying mother/father/child families we gained information on how much of the between-repeats variation is due to differences between and within repeat arrays on homologous chromosomes. Two instances in which a child exhibited more copies of a particular fragment than were present in the parents are described and hypothesized to be due to events such as multiple unequal sister-chromatid exchanges or gene conversions. PMID:8878694
Lindstrom, Derek L; Leverich, Christina K; Henderson, Kiersten A; Gottschling, Daniel E
Somatic mutations contribute to the development of age-associated disease. In earlier work, we found that, at high frequency, aging Saccharomyces cerevisiae diploid cells produce daughters without mitochondrial DNA, leading to loss of respiration competence and increased loss of heterozygosity (LOH) in the nuclear genome. Here we used the recently developed Mother Enrichment Program to ask whether aging cells that maintain the ability to produce respiration-competent daughters also experience increased genomic instability. We discovered that this population exhibits a distinct genomic instability phenotype that primarily affects the repeated ribosomal RNA gene array (rDNA array). As diploid cells passed their median replicative life span, recombination rates between rDNA arrays on homologous chromosomes progressively increased, resulting in mutational events that generated LOH at >300 contiguous open reading frames on the right arm of chromosome XII. We show that, while these recombination events were dependent on the replication fork block protein Fob1, the aging process that underlies this phenotype is Fob1-independent. Furthermore, we provide evidence that this aging process is not driven by mechanisms that modulate rDNA recombination in young cells, including loss of cohesion within the rDNA array or loss of Sir2 function. Instead, we suggest that the age-associated increase in rDNA recombination is a response to increasing DNA replication stress generated in aging cells.
Mahelka, Václav; Krak, Karol; Kopecký, David; Fehrer, Judith; Šafář, Jan; Bartoš, Jan; Hobza, Roman; Blavet, Nicolas; Blattner, Frank R.
The movement of nuclear DNA from one vascular plant species to another in the absence of fertilization is thought to be rare. Here, nonnative rRNA gene [ribosomal DNA (rDNA)] copies were identified in a set of 16 diploid barley (Hordeum) species; their origin was traceable via their internal transcribed spacer (ITS) sequence to five distinct Panicoideae genera, a lineage that split from the Pooideae about 60 Mya. Phylogenetic, cytogenetic, and genomic analyses implied that the nonnative sequences were acquired between 1 and 5 Mya after a series of multiple events, with the result that some current Hordeum sp. individuals harbor up to five different panicoid rDNA units in addition to the native Hordeum rDNA copies. There was no evidence that any of the nonnative rDNA units were transcribed; some showed indications of having been silenced via pseudogenization. A single copy of a Panicum sp. rDNA unit present in H. bogdanii had been interrupted by a native transposable element and was surrounded by about 70 kbp of mostly noncoding sequence of panicoid origin. The data suggest that horizontal gene transfer between vascular plants is not a rare event, that it is not necessarily restricted to one or a few genes only, and that it can be selectively neutral. PMID:28137844
Zehethofer, K; Sturmbauer, C
We have analyzed a sequence dataset of a portion of mitochondrial 12S rRNA gene of the ribosomal small subunit for 27 species of the family Lycosidae (wolf spiders) from Central Europe, belonging to six genera (Alopecosa, Arctosa, Pardosa, Pirata, Trochosa, and Xerolycosa) and four subfamilies (Evippinae, Lycosinae, Pardosinae and Venoniinae). Phylogenetic analyses were performed in two steps and corroborate the monophyly of all the genera analyzed with strong bootstrap support. In the first step focusing on the most ancestral splits the genus Pirata consistently emerged as the most ancestral branch, followed by the two genera Arctosa and Xerolycosa, with conflicting branching order, however. The second step of analysis placed Xerolycosa more ancestral than Arctosa. Arctosa appeared as sister group to the genera Alopecosa, Trochosa, and Pardosa. The palearctic genus Xerolycosa was not yet included in previous studies derived from morphological characters, but its placement based on mtDNA sequences is in good agreement to that according to current diagnostic morphological features. Further, the single representative of the genus Arctosa examined in our study was placed at a more ancestral position than in a previous investigation based on phenotypic characters. The superimposition of the currently used diagnostic phenotypic characters on the DNA-based phylogeny shows that both character sets are widely congruent; only 3 out of 16 phenotypic characters were resolved as homoplasious, suggesting their parallel evolution and/or reversal. Among the three different styles of predation found in the Lycosids, tube builders appear to be the most ancestral from which burrow dwellers descended and from which two groups of vagrant hunters evolved in parallel.
Paul, S S; Deb, S M; Dey, A; Somvanshi, S P S; Singh, D; Rathore, R; Stiverson, J
The molecular diversity of rumen methanogens was investigated using 16S rDNA gene library prepared from the rumen contents of Nili-Ravi buffaloes. Microbial genomic DNA was isolated from four adult male fistulated buffaloes and PCR conditions were set up using specific primers. Amplified product was cloned into a suitable vector, and the inserts of positive clones were sequenced. A total of 142 clones were examined, and the analysis revealed 46 species level (0.01 distance) operational taxonomic units (OTUs). Twenty six OTUs comprising 89 clones (63% of the total clones) were taxonomically assigned to Methanobacterium genus and the majority of them had highest percent identity with Methanobacterium flexile among cultured methanogens. Five OTUs comprising 27 clones (19% of total clones) were taxonomically assigned to Methanomicrobium genus and these clones showed highest sequence identity with Methanomicrobium mobile. Only two OTUs comprising 6 clones (4% of total clones) were assigned to Methanobrevibacter genus. A total of 17 clones belonging to 10 species level OTUs showed highest percent identity (ranging from 85 to 95%) with Methanomassilicoccus luminyensis and were taxonomically classified as Methanomassiliicocaceae. Out of the 142 rDNA clones, 112 clones, which constitute 79% of the total clones representing 42 OTUs, had less than 98.5% sequence identity with any of the cultured strains of methanogens and represent novel species of methanogens. This study has revealed the largest assortment of hydrogenotrophic methanogen phylotypes ever identified from the rumen of Nili-Ravi buffaloes. The study indicates that Methanobacterium is the most dominant methanogen in the rumen of Nili-Ravi buffalo. This is also the first report on the presence of methanogens phylogenetically close to M. luminyensis, an H2 dependent methylotrophic methanogen, in the rumen of buffaloes at such a high level of abundance.
Cutillas, C; Oliveros, R; de Rojas, M; Guevara, D C
Adults of Trichuris skrjahini have been isolated from the cecum of caprine hosts (Capra hircus), Trichuris ovis and Trichuris globulosa from Ovis aries (sheep) and C. hircus (goats), and Trichuris leporis from Lepus europaeus (rabbits) in Spain. Genomic DNA was isolated and the ITS1-5.8S-ITS2 segment from the ribosomal DNA (rDNA) was amplified and sequenced by polymerase chain reaction (PCR) techniques. The ITS1 of T. skrjabini, T. ovis, T. globulosa, and T. leporis was 495, 757, 757, and 536 nucleotides in length, respectively, and had G + C contents of 59.6, 58.7, 58.7, and 60.8%, respectively. Intraindividual variation was detected in the ITSI sequences of the 4 species. Furthermore, the 5.8S sequences of T. skrjabini, T. ovis, T. globulosa, and T. leporis were compared. A total of 157, 152, 153, and 157 nucleotides in length was observed in the 5.8S sequences of these 4 species, respectively. There were no sequence differences of ITS1 and 5.8S products between T. ovis and T. globulosa. Nevertheless, clear differences were detected between the ITS1 sequences of T. skrjabini, T. ovis, T. leporis, Trichuris muris, and T. arvicolae. The ITS2 fragment from the rDNA of T. skrjabini was sequenced. A comparative study of the ITS2 sequence of T. skrjabini with the previously published ITS2 sequence data of T. ovis, T. leporis, T. muris, and T. arvicolae suggested that the combined use of sequence data from both spacers would be useful in the molecular characterization of trichurid parasites.
Milhomem, Susana S R; Scacchetti, Priscilla C; Pieczarka, Julio C; Ferguson-Smith, Malcolm A; Pansonato-Alves, José C; O'Brien, Patricia C M; Foresti, Fausto; Nagamachi, Cleusa Y
Gymnotus (Gymnotiformes, Gymnotidae) is the most diverse known Neotropical electric knife fish genus. Cytogenetic studies in Gymnotus demonstrate a huge karyotypic diversity for this genus, with diploid numbers ranging from 34 to 54. The NOR are also variable in this genus, with both single and multiple NORs described. A common interpretation is that the single NOR pair is a primitive trait while multiple NORs are derivative. However this hypothesis has never been fully tested. In this report we checked if the NOR-bearing chromosome and the rDNA site are homeologous in different species of the genus Gymnotus: G. carapo (2n = 40, 42, 54), G. mamiraua (2n = 54), G. arapaima (2n = 44), G. sylvius (2n = 40), G. inaequilabiatus (2n = 54) and G. capanema (2n = 34), from the monophyletic group G. carapo (Gymnotidae-Gymnotiformes), as well as G. jonasi (2n = 52), belonging to the G1 group. They were analyzed with Fluorescence in situ hybridization (FISH) using 18S rDNA and whole chromosome probes of the NOR-bearing chromosome 20 (GCA20) of G. carapo (cytotype 2n = 42), obtained by Fluorescence Activated Cell Sorting. All species of the monophyletic G. carapo group show the NOR in the same single pair, confirmed by hybridization with CGA20 whole chromosome probe. In G. jonasi the NORs are multiple, and located on pairs 9, 10 and 11. In G. jonasi the GCA20 chromosome probe paints the distal half of the long arm of pair 7, which is not a NOR-bearing chromosome. Thus these rDNA sequences are not always in the homeologous chromosomes in different species thus giving no support to the hypothesis that single NOR pairs are primitive traits while multiple NORs are derived. The separation of groups of species in the genus Gymnotus proposed by phylogenies with morphologic and molecular data is supported by our cytogenetic data.
Dhar, S K; Choudhury, N R; Mittal, V; Bhattacharya, A; Bhattacharya, S
In the protozoan parasite Entamoeba histolytica (which causes amoebiasis in humans), the rRNA genes (rDNA) in the nucleus are carried on an extrachromosomal circular plasmid. For strain HM-1:IMSS, the size of the rDNA plasmid is 24.5 kb, and 200 copies per genome are present. Each circle contains two rRNA transcription units as inverted repeats separated by upstream and downstream spacers. We have studied the replication of this molecule by neutral/neutral two-dimensional gel electrophoresis and by electron microscopy. All restriction fragments analyzed by two-dimensional gel electrophoresis gave signals corresponding to simple Y's and bubbles. This showed that replication initiated in this plasmid at multiple, dispersed locations spread throughout the plasmid. On the basis of the intensity of the bubble arcs, initiations from the rRNA transcription units seemed to occur more frequently than those from intergenic spacers. Multiple, dispersed initiation sites were also seen in the rDNA plasmid of strain HK-9 when it was analyzed by two-dimensional gel electrophoresis. Electron microscopic visualization of replicating plasmid molecules in strain HM-1:IMISS showed multiple replication bubbles in the same molecule. The location of bubbles on the rDNA circle was mapped by digesting with PvuI or BsaHI, which linearize the molecule, and with SacII, which cuts the circle twice. The distance of the bubbles from one end of the molecule was measured by electron microscopy. The data corroborated those from two-dimensional gels and showed that replication bubbles were distributed throughout the molecule and that they appeared more frequently in rRNA transcription units. The same interpretation was drawn from electron microscopic analysis of the HK-9 plasmid. Direct demonstration of more than one bubble in the same molecule is clear evidence that replication of this plasmid initiates at multiple sites. Potential replication origins are distributed throughout the plasmid. Such a
Rogers, Scott O.; Bendich, Arnold J.
We have compared the restriction patterns and copy numbers of ribosomal RNA genes (rDNA) between and within individuals of Vicia faba . While the EcoRI blot-hybridization patterns changed only after one to two generations, copy number changes were found among different tissues of the same plant. Copy number differences among individuals in the population were as great as 95-fold, whereas as much as a 12-fold variation was seen among tissues of the same plant. Among individual F1 progeny from genetic crosses, nearly an 8-fold variation was seen, and among individuals of the F2 generation a spread of 22-fold was measured. Among individual siblings of self-pollinated parents, up to 7-fold variation was observed. However, changes in copy number did not necessarily indicate changes in rDNA EcoRI blot-hybridization pattern, and vice versa. Furthermore, nearest neighbor analysis of R-loop experiments showed that the arrangement of members of the "nontranscribed" spacer (NTS) size classes along the chromosome was not random, but some clustering was indicated. The data are consistent with the hypothesis that sister chromatid exchange in somatic cells of V. faba is the primary mechanism for altering the rDNA copy number as well as causing the extreme variation observed in the NTS. Variation among individuals in rDNA blot-hybridization pattern was also observed for Vicia villosa, Vicia dasycarpa, Vicia benghalensis and Vicia pannonica. PMID:17246404
Mishima, Y; Yamamoto, O; Kominami, R; Muramatsu, M
An in vitro transcription system which utilizes cloned mouse ribosomal RNA gene (rDNA) fragments and a mouse cell extract has been developed. RNA polymerases I is apparently responsible for this transcription as evidenced by the complete resistance to a high concentration (200 micrograms/ml) of alpha-amanitin. Run-off products obtained with three different truncated rDNA fragments indicated that RNA was transcribed from a unique site of rDNA. The S1 nuclease protection mapping of the in vitro product and of in vivo 45S RNA confirmed this site, indicating that, in this in vitro system, transcription of rDNA started from the same site as in vivo. This site is located at several hundred nucleotides upstream from the putative initiation site reported by us (1) and by others (2). Some sequence homology surrounding this region was noted among mouse, Xenopus laevis and Drosophila melanogaster. The data also suggest that some processing of the primary transcript occurs in this in vitro system. Images PMID:6278446
Tengs, Torstein; Bowers, Holly A; Glasgow, Howard B; Burkholder, JoAnn M; Oldach, David W
Complete small subunit ribosomal RNA, internal transcribed spacer 1 and 2, 5.8S, and partial large subunit ribosomal RNA gene sequences were generated from multiple isolates of Pfiesteria piscicida. Sequences were derived from isolates that have been shown to be ichthyotoxic as well as isolates that have no history of toxic behavior. All of the sequences generated were identical for the different cultures, and we therefore conclude that differences in toxicity seen between isolates of P. piscicida are linked to factors other than genetic strain variation detectable by ribosomal gene sequence analyses.
Junéra, H R; Masson, C; Géraud, G; Suja, J; Hernandez-Verdun, D
The distribution of the ribosomal genes (rDNA) and the upstream binding factor (UBF), correlatively with their RNA transcripts, was investigated in G1, S-phase, and G2. rDNA was distributed in nucleoli, with alternate sites of clustered and dispersed genes. UBF was found associated with some but not all clustered genes and proportionally more with dispersed genes. It was distributed in several foci that were more numerous and heterogeneous in size during G2 than G1. We suggest that UBF associated with rDNA during S-phase because its nucleolar amount increased during that time and remained stable in G2. 5,6-Dichloro-1-beta-D-ribofuranosylbenzimidazole treatment indicated a similar amount of UBF per transcription unit, and consequently heterogeneous size of the UBF foci can represent a variable number of transcription units per foci. Direct visualization of the transcripts demonstrated that only part of UBF is associated with active transcription and that rDNA distribution varied with transcription. We propose that in the same rDNA locus three types of configuration coexist that are correlated with gene activity: 1) clustered genes without UBF; 2) clustered genes with UBF, of which some are associated with transcription; and 3) dispersed genes with UBF and transcription. These results support the hypothesis that rDNA transcription involved several steps of regulation acting successively and locally in the same locus to promote the repressed clustered genes to become actively transcribed dispersed genes. Images PMID:9017602
Gornung, Ekaterina; Colangelo, Paolo; Annesi, Flavia
This paper describes a study of the 5S ribosomal RNA genes (5S rDNA) in a group of 6 species belonging to 4 genera of Mugilidae. In these 6 species, the relatively short 5S rDNA repeat units, generated by PCR and ranging in size from 219 to 257 bp, show a high level of intragenomic homogeneity of both coding and spacer regions (NTS-I). Phylogenetic reconstructions based on this data set highlight the greater phylogenetic and genetic diversity of Mugil cephalus and Oedalechilus labeo compared with the genera Liza and Chelon. Comparative sequence analysis revealed significant conservation of the short 5S rDNA repeat units across Chelon and Liza. Moreover, a second size class of 5S rDNA repeat units, ranging from roughly 800 to 1100 bp, was produced in the Liza and Chelon samples. Only short 5S rDNA repeat units were found in M. cephalus and O. labeo. The sequences of the long 5S rDNA repeat units, obtained in Chelon labrosus and Liza ramada, differ owing to the presence of 2 large insertion/deletions (indels) in the spacers (NTS-II) and show considerable sequence identity with NTS-I spacers. Interspecific sequence variation of NTS-II spacers, excluding the indels, is low. Southern-blot hybridization patterns suggest an intermixed arrangement of short and long repeat units within a single chromosome locus.
González-Melendi, P; Wells, B; Beven, A F; Shaw, P J
The rDNA transcription units are enormous macromolecular structures located in the nucleolus and containing 50-100 RNA polymerases together with the nascent pre-rRNA attached to the rDNA. It has not previously been possible to visualize nucleolar transcription units directly in intact nucleoli, although highly spread preparations in the electron microscope have been imaged as "Christmas trees" 2-3 microm long. Here we determine the relative conformation of individual transcription units in Pisum sativum plant nucleoli using a novel labelling technique. Nascent transcripts were detected by a highly sensitive silver-enhanced 1 nm gold procedure, followed by 3D electron microscopy of entire nucleoli. Individual transcription units are seen as conical, elongated clusters approximately 300 nm in length and 130 nm in width at the thickest end. We further show that there were approximately 300 active ribosomal genes in the nucleoli examined. The underlying chromatin structure of the transcribing rDNA was directly visualized by applying a novel limited extraction procedure to fixed specimens in order to wash out the proteins and RNA, thus specifically revealing DNA strands after uranyl acetate staining. Using this technique, followed by post-embedding in situ hybridization, we observed that the nucleolar rDNA fibres are not extended but show a coiled, thread-like appearance. Our results show for the first time that native rDNA transcription units are linear, compacted Christmas trees.
Tang, Cuong Q; Leasi, Francesca; Obertegger, Ulrike; Kieneke, Alexander; Barraclough, Timothy G; Fontaneto, Diego
Molecular tools have revolutionized the exploration of biodiversity, especially in organisms for which traditional taxonomy is difficult, such as for microscopic animals (meiofauna). Environmental (eDNA) metabarcode surveys of DNA extracted from sediment samples are increasingly popular for surveying biodiversity. Most eDNA surveys use the nuclear gene-encoding small-subunit rDNA gene (18S) as a marker; however, different markers and metrics used for delimiting species have not yet been evaluated against each other or against morphologically defined species (morphospecies). We assessed more than 12,000 meiofaunal sequences of 18S and of the main alternatively used marker [Cytochrome c oxidase subunit I (COI) mtDNA] belonging to 55 datasets covering three taxonomic ranks. Our results show that 18S reduced diversity estimates by a factor of 0.4 relative to morphospecies, whereas COI increased diversity estimates by a factor of 7.6. Moreover, estimates of species richness using COI were robust among three of four commonly used delimitation metrics, whereas estimates using 18S varied widely with the different metrics. We show that meiofaunal diversity has been greatly underestimated by 18S eDNA surveys and that the use of COI provides a better estimate of diversity. The suitability of COI is supported by cross-mating experiments in the literature and evolutionary analyses of discreteness in patterns of genetic variation. Furthermore its splitting of morphospecies is expected from documented levels of cryptic taxa in exemplar meiofauna. We recommend against using 18S as a marker for biodiversity surveys and suggest that use of COI for eDNA surveys could provide more accurate estimates of species richness in the future.
Wubet, Tesfaye; Weiss, Michael; Kottke, Ingrid; Teketay, Demel; Oberwinkler, Franz
The endangered indigenous tree species Juniperus procera, commonly known as African Pencil Cedar, is an important component of the dry Afromontane vegetation of Ethiopia and was shown to be AM in earlier studies. Here we describe the composition of AM fungi in colonized roots of J. procera from two dry Afromontane forests of Ethiopia. The nuSSU rDNA gene was amplified from colonized roots, cloned and sequenced using AM fungal specific primers that were partly developed for this study. Molecular phylogenetic analysis revealed that all the glomeralean sequences obtained belonged exclusively to the genus Glomus (Glomeraceae). Seven distinct Glomus sequence types were identified that all are new to science. The composition of the AM fungal communities between the sampled trees, and between the two study sites in general, differed significantly. Isolation and utilization of the indigenous AM fungal taxa from the respective sites might be required for successful enrichment plantation of this threatened Juniperus species.
Yokobori, Shin-Ichi; Kurabayashi, Atsushi; Neilan, Brett A; Maruyama, Tadashi; Hirose, Euichi
In the tropics, certain didemnid ascidians harbor the prokaryotic photosymbiont Prochloron. To date, this photosymbiosis has been found in four didemnid genera that include non-symbiotic species. Here, we report the molecular phylogeny of symbiotic and non-symbiotic didemnids based on their 18S rDNA sequences. The data cover all four genera containing symbiotic species and one other genus comprised of only non-symbiotic species. Near-complete nucleotide sequences of 18S rDNAs were determined for four non-didemnid species and 52 didemnid samples (five genera), including 48 photosymbiotic samples collected from the Ryukyu Archipelago, the Great Barrier Reef, Hawaii, and Bali. Our phylogenetic trees indicated a monophyletic origin of the family Didemnidae, as well as each of the didemnid genera. The results strongly support the hypothesis that establishment of the ascidian-Prochloron symbiosis occurred independently in the Didemnidae lineage at least once in each of the genera that possess symbiotic species.
Stenøien, H K
The evolutionary potential of bryophytes (mosses, liverworts and hornworts) has been debated for decades. Fossil record and biogeographical distribution patterns suggest very slow morphological evolution and the retainment of several ancient traits since the split with vascular plants some 450 million years ago. Many have argued that bryophytes may evolve as rapidly as higher plants on the molecular level, but this hypothesis has not been tested so far. Here, it is shown that mosses have experienced significantly lower rates of molecular evolution than higher plants within 18S rDNA (nuclear), rbcL (chloroplast) and nad5 (mitochondrial) genes. Mosses are on an average evolving 2-3 times slower than ferns, gymnosperms and angiosperms; and also green algae seem to be evolving faster than nonvascular plants. These results support the observation of a general correlation between morphological and molecular evolutionary rates in plants and also show that mosses are 'evolutionary sphinxes' regarding both morphological and molecular evolutionary potential.
MOHANTA, Uday Kumar; ITAGAKI, Tadashi
Linguatula serrata, a cosmopolitan parasite, is commonly known as tongue worm belonging to the subclass Pentastomida.We collected the nymphal stage of the worm from mesenteric lymph nodes of cattle and identified these as L. serrata based on morphology and morphometry. The 18S rDNA sequences showed no intraspecific v