scholarly journals Phenotypic effects of targeted mutations in the small subunit rRNA gene of Tetrahymena thermophila.

1993 ◽  
Vol 13 (8) ◽  
pp. 4814-4825 ◽  
Author(s):  
R Sweeney ◽  
L Chen ◽  
M C Yao
Keyword(s):  
Tertiary Structure ◽  
Tetrahymena Thermophila ◽  
Ribosomal Subunit ◽  
Small Subunit ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Small Subunit Rrna ◽  
Variable Regions ◽  
Small Subunit Rrna Gene

Tetrahymena thermophila is an ideal organism with which to study functional aspects of the rRNAs in vivo since the somatic rRNA genes of T. thermophila can be totally replaced by cloned copies introduced via microinjection. In this study, we made small insertions into seven sites within the small subunit rRNA gene and observed their phenotypic effects on transformed cells. Two mutated genes coding for rRNA (rDNAs), both of which bear insertions in highly conserved sequences, failed to transform and are therefore believed to produce nonfunctional rRNAs. Three other altered rDNAs produce functional rRNAs that can substitute for most or all of the cellular rRNA. Two of these bear insertions in highly variable regions, and, surprisingly, the other has an insertion in a region that is well conserved for both sequence and secondary structure among eucaryotes. In addition, two other insertions appear to destabilize rRNAs that contain them. Our findings make predictions concerning the positions of some of these sites within the tertiary structure of the small ribosomal subunit and thus serve as an in vivo test of the existing tertiary structure models for the small subunit rRNA. Our results are in good agreement with expectations based on sequence comparison and in vitro work.

Phenotypic effects of targeted mutations in the small subunit rRNA gene of Tetrahymena thermophila

1993 ◽  
Vol 13 (8) ◽  
pp. 4814-4825
Author(s):  
R Sweeney ◽  
L Chen ◽  
M C Yao
Keyword(s):  
Tertiary Structure ◽  
Tetrahymena Thermophila ◽  
Ribosomal Subunit ◽  
Small Subunit ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Small Subunit Rrna ◽  
Variable Regions ◽  
Small Subunit Rrna Gene

Tetrahymena thermophila is an ideal organism with which to study functional aspects of the rRNAs in vivo since the somatic rRNA genes of T. thermophila can be totally replaced by cloned copies introduced via microinjection. In this study, we made small insertions into seven sites within the small subunit rRNA gene and observed their phenotypic effects on transformed cells. Two mutated genes coding for rRNA (rDNAs), both of which bear insertions in highly conserved sequences, failed to transform and are therefore believed to produce nonfunctional rRNAs. Three other altered rDNAs produce functional rRNAs that can substitute for most or all of the cellular rRNA. Two of these bear insertions in highly variable regions, and, surprisingly, the other has an insertion in a region that is well conserved for both sequence and secondary structure among eucaryotes. In addition, two other insertions appear to destabilize rRNAs that contain them. Our findings make predictions concerning the positions of some of these sites within the tertiary structure of the small ribosomal subunit and thus serve as an in vivo test of the existing tertiary structure models for the small subunit rRNA. Our results are in good agreement with expectations based on sequence comparison and in vitro work.

Morphological studies and molecular data on a new marine ciliate, Apokeronopsis sinica n. sp. (Ciliophora: Urostylida), from the South China Sea

Zootaxa ◽  
2009 ◽  
Vol 2005 (1) ◽  
pp. 57-66 ◽  
Author(s):  
WEIWEI LIU ◽  
JIQIU LI ◽  
SHAN GAO ◽  
CHEN SHAO ◽  
JUN GONG ◽  
...  
Keyword(s):  
Molecular Data ◽  
Small Subunit ◽  
Rrna Gene ◽  
Small Subunit Rrna ◽  
Cortical Granules ◽  
Marine Ciliate ◽  
Morphological Studies ◽  
Small Subunit Rrna Gene ◽  
Morphological And Molecular Data

The morphology of a new marine urostylid ciliate, Apokeronopsis sinica n. sp., collected from the Clear Water Bay, Hong Kong, was investigated. Additionally, the SSrRNA gene was sequenced in order to make a comparison at molecular level. Based on both morphological and molecular data, descriptions and comparisons with its congeners are provided. Apokeronopsis sinica is characterized by: body size about 150–200 × 50–65 µm in vivo; two kinds of cortical granules; about 20 cirri in frontal area which form the non-typical bicorona; 2 frontoterminal, ca. 4 buccal and 10 transverse cirri; midventral complex consists of 21–32 pairs of cirri; on average 35 right and 30 left marginal cirri; about 50 membranelles; invariably 3 dorsal kineties. A key to the identification of the known Apokeronopsis species was suggested. The small subunit rRNA gene sequence differences between Apokeronopsis sinica and its congeners range from 1.64% to 3.72%.

scholarly journals Parabirojimia multinucleata spec. nov. and Anteholosticha scutellum (Cohn, 1866) Berger, 2003, marine ciliates (Ciliophora, Hypotrichida) from tropical waters in southern China, with notes on their small-subunit rRNA gene sequences

2010 ◽  
Vol 60 (1) ◽  
pp. 234-243 ◽  
Author(s):  
Xiangrui Chen ◽  
Shan Gao ◽  
Weibo Song ◽  
Khaled A. S. Al-Rasheid ◽  
Alan Warren ◽  
...  
Keyword(s):  
Southern China ◽  
Small Subunit ◽  
Rrna Gene ◽  
Small Subunit Rrna ◽  
Cortical Granules ◽  
Morphological Studies ◽  
Small Subunit Rrna Gene ◽  
New Information ◽  
Modern Methods

Few studies using modern methods have been carried out on ciliated protozoa in tropical marine waters. In the present work, two hypotrichs, Parabirojimia multinucleata spec. nov. and Anteholosticha scutellum (Cohn, 1866) Berger, 2003, collected from Daya Bay in southern China, were investigated morphologically. P. multinucleata is distinguished by the following combination of characters: slender body, without a snout-like protrusion in the frontal field, and about 50 macronuclear nodules. The poorly known A. scutellum has never been investigated using modern methods; hence, a redescription is needed. During the present study, observations of specimens in vivo and following protargol impregnation revealed new information concerning structures such as the cortical granules and the infraciliature. A redescription and improved diagnosis are supplied based on the China population. The small-subunit (SSU) rRNA gene was sequenced for both organisms and comparisons with those of similar congeners clearly support the findings based on morphological studies.

Redescriptions of three trachelocercid ciliates (Protista, Ciliophora, Karyorelictea), with notes on their phylogeny based on small subunit rRNA gene sequences

2013 ◽  
Vol 63 (Pt_9) ◽  
pp. 3506-3514 ◽  
Author(s):  
Ying Yan ◽  
Yuan Xu ◽  
Zhenzhen Yi ◽  
Alan Warren
Keyword(s):  
Sequence Data ◽  
Phylogenetic Analyses ◽  
Small Subunit ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Ssu Rrna ◽  
Small Subunit Rrna ◽  
Small Subunit Rrna Gene ◽  
Ssu Rrna Gene Sequence ◽  
First Time

Three trachelocercid ciliates, Kovalevaia sulcata (Kovaleva, 1966) Foissner, 1997, Trachelocerca sagitta (Müller, 1786) Ehrenberg, 1840 and Trachelocerca ditis (Wright, 1982) Foissner, 1996, isolated from two coastal habitats at Qingdao, China, were investigated using live observation and silver impregnation methods. Data on their infraciliature and morphology are supplied. The small subunit rRNA (SSU rRNA) genes of K. sulcata and Trachelocerca sagitta were sequenced for the first time. Phylogenetic analyses based on SSU rRNA gene sequence data indicate that both organisms, and the previously sequenced Trachelocerca ditis, are located within the trachelocercid assemblage and that K. sulcata is sister to an unidentified taxon forming a clade that is basal to the core trachelocercids.

scholarly journals Regulation of Plasmodium yoelii Oocyst Development by Strain- and Stage-Specific Small-Subunit rRNA

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Yanwei Qi ◽  
Feng Zhu ◽  
Richard T. Eastman ◽  
Young Fu ◽  
Martine Zilversmit ◽  
...  
Keyword(s):  
Developmental Stages ◽  
Small Subunit ◽  
Plasmodium Yoelii ◽  
Rrna Genes ◽  
Parasite Development ◽  
Rrna Gene ◽  
Small Subunit Rrna ◽  
Malaria Parasites ◽  
Content Type ◽  
Small Subunit Rrna Gene

ABSTRACT One unique feature of malaria parasites is the differential transcription of structurally distinct rRNA (rRNA) genes at different developmental stages: the A-type genes are transcribed mainly in asexual stages, whereas the S-type genes are expressed mostly in sexual or mosquito stages. Conclusive functional evidence of different rRNAs in regulating stage-specific parasite development, however, is still absent. Here we performed genetic crosses of Plasmodium yoelii parasites with one parent having an oocyst development defect (ODD) phenotype and another producing normal oocysts to identify the gene(s) contributing to the ODD. The parent with ODD—characterized as having small oocysts and lacking infective sporozoites—was obtained after introduction of a plasmid with a green fluorescent protein gene into the parasite genome and subsequent passages in mice. Quantitative trait locus analysis of genome-wide microsatellite genotypes of 48 progeny from the crosses linked an ~200-kb segment on chromosome 6 containing one of the S-type genes (D-type small subunit rRNA gene [D-ssu]) to the ODD. Fine mapping of the plasmid integration site, gene expression pattern, and gene knockout experiments demonstrated that disruption of the D-ssu gene caused the ODD phenotype. Interestingly, introduction of the D-ssu gene into the same parasite strain (self), but not into a different subspecies, significantly affected or completely ablated oocyst development, suggesting a stage- and subspecies (strain)-specific regulation of oocyst development by D-ssu. This study demonstrates that P. yoelii D-ssu is essential for normal oocyst and sporozoite development and that variation in the D-ssu sequence can have dramatic effects on parasite development. IMPORTANCE Malaria parasites are the only known organisms that express structurally distinct rRNA genes at different developmental stages. The differential expression of these genes suggests that they play unique roles during the complex life cycle of the parasites. Conclusive functional proof of different rRNAs in regulating parasite development, however, is still absent or controversial. Here we functionally demonstrate for the first time that a stage-specifically expressed D-type small-subunit rRNA gene (D-ssu) is essential for oocyst development of the malaria parasite Plasmodium yoelii in the mosquito. This study also shows that variations in D-ssu sequence and/or the timing of transcription may have profound effects on parasite oocyst development. The results show that in addition to protein translation, rRNAs of malaria parasites also regulate parasite development and differentiation in a strain-specific manner, which can be explored for controlling parasite transmission.

scholarly journals The small ribosomal subunit RNA isoforms in Plasmodium cynomolgi.

Genetics ◽  
1994 ◽  
Vol 136 (3) ◽  
pp. 857-865 ◽  
Author(s):  
V Corredor ◽  
V Enea
Keyword(s):  
Ribosomal Subunit ◽  
Plasmodium Species ◽  
Single Copy ◽  
Small Subunit ◽  
Rrna Genes ◽  
Last Common Ancestor ◽  
Small Subunit Rrna ◽  
Specific Sequence ◽  
Variable Regions ◽  
Plasmodium Cynomolgi

Abstract We report the isolation, characterization and analysis of the small subunit rRNA genes in Plasmodium cynomolgi (Ceylon). As in other Plasmodium species, these genes are present in low copy number, are unlinked and form two types that are distinct in sequence and are expressed stage specifically. The asexually expressed (type A) genes are present in four copies in the Ceylon- and in five copies in the Berok-strain. Surprisingly, the sexually expressed (type B) gene is present in a single copy. The vast majority of the differences between gene types is confined to the variable regions. The pattern of divergence is different from that observed in Plasmodium berghei or in Plasmodium falciparum. Analysis of the small subunit rRNA sequences of P. cynomolgi, P. berghei and P. falciparum, indicates that the two gene types do not evolve independently but rather interact (through gene conversion or some form of recombination) to such an extent as to erase whatever stage-specific sequence signatures they may have had in the last common ancestor.

Morphology, morphogenesis and small-subunit rRNA gene sequence of the novel brackish-water ciliate Strongylidium orientale sp. nov. (Ciliophora, Hypotrichia)

2013 ◽  
Vol 63 (Pt_3) ◽  
pp. 1155-1164 ◽  
Author(s):  
Xumiao Chen ◽  
Miao Miao ◽  
Honggang Ma ◽  
Chen Shao ◽  
Khaled A. S. Al-Rasheid
Keyword(s):  
De Novo ◽  
Southern China ◽  
Phylogenetic Analyses ◽  
Small Subunit ◽  
Rrna Gene ◽  
Small Subunit Rrna ◽  
Cortical Granules ◽  
Posterior Portion ◽  
Small Subunit Rrna Gene

A novel stichotrich ciliate, Strongylidium orientale sp. nov., was discovered from a mangrove river in Hong Kong, southern China, and its morphology was investigated through observations in vivo and after protargol impregnation. Cells are 80–120×35–50 µm in vivo and fusiform in shape, with rounded anterior and tapered posterior ends. It is characterized by its brackish habitat and by the presence of two types of cortical granules arranged irregularly throughout the cortex. Morphogenetic events of cell division and physiological reorganization are described. The main ontogenetic features were: (i) only the posterior portion of the parental adoral zone of membranelles was renewed by dedifferentiation of the old structures; (ii) the oral primordium in the opisthe occurred apokinetally; (iii) the left and right ventral rows originated intrakinetally and the final left ventral row was spliced from two cirri from the frontoventral cirral anlage, a short cirral row from the anlage for the right ventral row and a long cirral row which was formed from the whole anlage of the left ventral row; (iv) the marginal rows developed intrakinetally; (v) the dorsal kineties replicated entirely de novo and did not fragment; and (vi) the two macronuclear nodules fused into a mass and then divided. Based on small-subunit rRNA gene sequences, phylogenetic analyses showed a close relationship with its congener Strongylidium pseudocrassum and with the genus Pseudouroleptus.

Phasmarhabditis kenyaensis n. sp. (Nematoda: Rhabditidae) from the slug, Polytoxon robustum, in Kenya

Nematology ◽  
2020 ◽  
pp. 1-17
Author(s):  
Annika Pieterse ◽  
Ben Rowson ◽  
Louwrens Tiedt ◽  
Antoinette P. Malan ◽  
Solveig Haukeland ◽  
...  
Keyword(s):  
New Species ◽  
Phylogenetic Analyses ◽  
Ribosomal Subunit ◽  
Small Subunit ◽  
Infective Juvenile ◽  
Bootstrap Support ◽  
Body Region ◽  
Rrna Gene ◽  
Small Subunit Rrna

Summary A new species of Phasmarhabditis was isolated from the slug, Polytoxon robustum, from Nairobi, Kenya. The nematode was identified using morphological, morphometric, molecular and phylogenetic analyses. Phasmarhabditis kenyaensis n. sp. is characterised by an infective juvenile with the longest body length in the genus, measuring 1232 (1107-1336) μm, by the presence of males with a bursa bearing nine bilateral pairs of genital bursal papillae and one pair of papilliform phasmids flanking the tail, cephalate paired spicules, with an arc length of 71 (57-81) μm, as well as by females with a vulva located at the mid-body region and a conoid tail shape, with two phasmids located at ca 40% of the tail length. The molecular phylogeny of the new species, as inferred from its SSU (small subunit) rRNA gene, places P. kenyaensis n. sp. genetically close to undescribed phasmarhabditids from South Africa, suggesting an African grouping, while the D2-D3 (large ribosomal subunit) and ITS region analyses relate P. kenyaensis n. sp. to P. meridionalis, with weak bootstrap support. This is the third new Phasmarhabditis species described from the African continent, the new species bringing the total known complement of the genus to 14 species. A morphometric compendium to all species cultured in vivo is supplied.

Establishing mono-eukaryotic Histomonas meleagridis cultures from in vivo infection contaminated with Tetratrichomonas gallinarum and Blastocystis spp.

Parasitology ◽  
2013 ◽  
Vol 140 (10) ◽  
pp. 1266-1274 ◽  
Author(s):  
ANH DAO NGUYEN PHAM ◽  
JAN MAST ◽  
JEROEN KOEN DE GUSSEM ◽  
LARRY R. MCDOUGALD ◽  
BRUNO MARIA GODDEERIS
Keyword(s):  
Culture Media ◽  
Pcr Amplification ◽  
Small Subunit ◽  
Rrna Gene ◽  
Small Subunit Rrna ◽  
Morphological Evaluation ◽  
Small Subunit Rrna Gene ◽  
Transmission Electron ◽  
Successful Approach

SUMMARYThe necessity to easily establish Histomonas meleagridis cultures has been underlined extensively by many researchers in order to gain more insights in the biology of H. meleagridis. In addition the occurrence of different protozoa in the caeca of birds impedes, however, the isolation and propagation of H. meleagridis from field outbreaks. Therefore, in a kinetic study using transmission electron microscopy the deleterious effects of adventitious protozoa including Tetratrichomonas gallinarum and Blastocystis spp. on cultured H. meleagridis were examined. To overcome this issue, an easy and successful approach to establish the mono-eukaryotic H. meleagridis culture free of other host's protozoa is proposed. At 10 days post infection, liver lesions of H. meleagridis-infected birds were isolated and inoculated into culture media pre-incubated with caecal bacteria. After 48 h of incubation, presence of H. meleagridis in the cultures was confirmed through morphological evaluation. Additionally, TEM examination and analysis by PCR amplification of the small subunit rRNA gene could exclude the co-cultivation of T. gallinarum and Blastocystis spp. Furthermore, after successful propagation and maintenance of the cultured H. meleagridis, its pathogenicity was affirmed in an infection experiment in turkeys.

Morphology and small-subunit rRNA gene sequences of two novel marine ciliates, Metanophrys orientalis spec. nov. and Uronemella sinensis spec. nov. (Protista, Ciliophora, Scuticociliatia), with an improved diagnosis of the genus Uronemella

2013 ◽  
Vol 63 (Pt_9) ◽  
pp. 3515-3523 ◽  
Author(s):  
Xuming Pan ◽  
Mingzhuang Zhu ◽  
Honggang Ma ◽  
Khaled A. S. Al-Rasheid ◽  
Xiaozhong Hu
Keyword(s):  
Body Length ◽  
Phylogenetic Analyses ◽  
Small Subunit ◽  
Contractile Vacuole ◽  
Rrna Gene ◽  
Small Subunit Rrna ◽  
Gene Sequences ◽  
Marine Habitat ◽  
Small Subunit Rrna Gene

The morphology and infraciliature of two novel marine scuticociliates, Metanophrys orientalis spec. nov. and Uronemella sinensis spec. nov., collected from sandy beaches at Qingdao, China, were investigated using live observation and protargol-staining methods. Metanophrys orientalis spec. nov. is distinguished by the following characteristics: marine habitat and a slender to elongate oval body with pointed anterior end and rounded caudal end, in vivo about 25–50 µm long; buccal field about a quarter to a third of body length; nine or ten somatic kineties with dikinetids approximately in anterior half of body, monokinetids in posterior half; membranelles 1 and 2 almost equal in length and composed of two and three longitudinal rows of kinetids respectively; paroral membrane with zigzag structure extending anteriorly to middle portion of membranelle 2; contractile vacuole pore located at posterior end of somatic kinety 1. The genus Uronemella is redefined as follows: marine form with an elongate-elliptical or inverted pear-shaped body; apical plate conspicuous; buccal field about two-thirds of body length, cytostome subequatorially located; oral apparatus Uronema-like; somatic kineties comprising a mixture of dikinetids and monokinetids. Uronemella sinensis spec. nov. is recognized by having an elongate-elliptical body with truncated apical frontal plate, size in vivo about 25–35×15–20 µm, nine or ten somatic kineties, membranelle 1 consisting of two or three basal bodies, contractile vacuole pore at posterior end of somatic kinety 1. This study also compared the small-subunit rRNA gene sequences of these two species with other closely related species to show the sequence divergence, which ranged from 3.53 to 9.60 %. Phylogenetic analyses support the contention that the genus Uronemella is monophyletic, while Metanophrys is non-monophyletic.

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