Paraurostyla Weissei Research Articles

The total conjugation process of the free-living ciliate Paraurostyla weissei (Ciliophora: Spirotrichea): the unexpected response to unfavorable fluctuations in the environment

This study presents a light microscopy observation of the life cycle of the hypotrich ciliate, Paraurostyla weissei. The main aim of this study was to find out the primary reaction of the species P. weissei through the changing environmental conditions. First, the reaction to favorable conditions – asexual binary cell division was observed. The asexual division was a response to the persisting original conditions, which resulted in an overgrowth of cultures. Subsequently, the changes in culture conditions in two groups of watch glasses were tested. The first group of watch glasses was characterised by gradual dehydration, loss of living space and lack of food. Here, the unexpected total conjugation process was identified, and this rare process was characterised as a priority response of the Paraurostyla species to the unfavorable conditions. This is the first reference not to the course of the conjugation process, but to the fact that not only the formation of resting cysts, but also total conjugation can be an important adaptation strategy of the ciliates. Secondly, a gradual decrease in temperature associated with slower drying was tested. The observation result was almost an unchanged state in cultures. Just before the samples completely dried, the cells reacted by cell death. The finding of the inability to stimulate the encystation process of a relatively common hypotrich species was unexpected. Finally, the total conjugation process in the first group of tested cultures was a priority response to altered conditions. The aim was also to point out the plasticity of adaptation mechanisms within the life cycle of P. weissei.

Reevaluation of the ‘well-known’ Paraurostyla weissei complex, with notes on the ontogenesis of a new Paraurostyla species (Ciliophora, Hypotrichia)

Two hypotrichous ciliates, Paraurostyla wuhanensis nov. spec. from Wuhan (China) and a new North American population of the Paraurostyla weissei complex, were studied based on live observations and protargol impregnation. Paraurostyla wuhanensis nov. spec. differs from the congeners by the combined features of having six or seven frontal cirri, 2–4 frontoventral cirri, 5–7 ventral rows, and yellow-greenish cortical granules. Ontogenesis proceeds as in the type species, except that fewer frontoventral cirri are formed in the new species. The morphology of the new population of the Paraurostyla weissei complex corresponds well with other American populations. In the phylogenetic trees based on the 18S rRNA gene, Paraurostyla sequences nest in a large clade together with Apoamphisiella and Notohymena. Monophyly of Paraurostyla is rejected by the results of the approximately unbiased test analyses. Morphological, morphogenetic, and phylogenetic analyses show a close relationship between the North American populations of the Paraurostyla weissei complex and Apoamphisiella, indicating that the taxonomic position of the former needs to be reassigned. A new combination, viz. Apoamphisiella polymicronucleata (Merriman, 1937) comb. nov., a reevaluation of the Paraurostyla weissei complex, and emended diagnoses of Paraurostyla and Apoamphisiella, are provided.

Taxonomic and Morphogenetic Description of the Freshwater Ciliate Aponotohymena isoaustralis n. sp. (Ciliophora; Oxytrichidae) Isolated from Sanjay Lake, Delhi, India

Morphology, morphogenesis and molecular phylogeny of a freshwater oxytrichid ciliate, Aponotohymena isoaustralis n. sp. collected from Sanjay Lake (28°36′51″N, 77°18′14″E), Delhi, India, were studied. The described species is characterized by a flexible body, with body size (in vivo) of about 148 × 46 µm and yellowish green cortical granules. Morphological characters exhibit: undulating membranes in Notohymena–pattern; two macronuclei and absence of micronucleus (amicronucleate); about 36 adoral membranelles; 18 frontoventral-transverse (FVT) cirri; one right and one left marginal row separated posteriorly; 6 dorsal rows; 7 caudal cirri arranged in 2 + 2 + 3 pattern (constant). In the present study, a detailed description of all the developmental stages is also provided. Prominent distinguishing features of the new species are the absence of micronucleus, 7 caudal cirri (constant), yellowish green cortical granules aligned along the margins and irregularly distributed throughout the cell. They may also be randomly concentrated as clusters along the left margin and posterior end of the cell. Molecular phylogeny based on small subunit rDNA sequence data suggests sister relationship of Aponotohymena isoaustralis n. sp. with Notohymena apoaustralis and Aponotohymena australis (Notohymena australis) which cluster in a clade with Paraurostyla weissei and Paraurostyla coronata. Further analysis of nucleotide sequence of SSU rDNA also suggests that A. isoaustralis n. sp. is distinct from the type species A. australis.

Physiological reorganization in the hypotrich ciliate Apoamphisiella vernalis (Protista, Ciliophora, Hypotricha)

Physiological reorganization is described for the first timed for the hypotrichous ciliate genus Apoamphisiella FOISSNER, 1997, based on a population of A. vernalis (STOKES, 1887) BERGER, 2006 collected from an eutrophic pond in the state of Minas Gerais, Brazil. Stomatogenesis is epiapokinetal, and the cirral pattern reorganizes from six typical fronto-ventral-transverse primordia, plus at least one short primordium located between IV and V. Primordia I and II originate from disaggregating undulating membranes and buccal cirrus, respectively; primordium III originates from left frontoventral cirrus plus a streak of basal bodies extending from the distal end of oral primordium; primordium IV and the short extra primordia are formed from basal bodies perhaps associated to the proximal end of III plus the disaggregation of anteriormost cirri of the left ventral row. Sometimes, the right frontoventral cirrus is incorporated by primordium IV. Primordia V and VI arise within the right ventral row as a single streak, splitting to form the two primordia. Marginal primordia develop initially within the pre-existent marginal rows, continuing to reorganize outside, pushing the old marginal cirri leftwards. Two dorsomarginal kineties develop associated to the right marginal row primordium. Dorsal ciliature also reorganizes from within the pre-existent dorsal kineties. The two macronuclear nodules approach each in middle reorganizers, briefly touching each other. At least one micronucleus undergo division. The process of physiological reorganization in A. vernalis resembles that of the North American Paraurostyla weissei complex representative, and along with features of the interphase morphology, indicate that Apoamphisiella belongs or is related to the Cyrtohymena-Paraurostyla group, within the Dorsomarginalia BERGER, 2006.

Ontogeny and Molecular Phylogeny of Apoamphisiella vernalis Reveal Unclear Separation between Genera Apoamphisiella and Paraurostyla (Protozoa, Ciliophora, Hypotricha).

Morphology and divisional morphogenesis of the hypotrich ciliate Apoamphisiella vernalis are investigated based on two populations from Brazil. Typical specimens of A. vernalis replicates its ventral ciliature from six fronto-ventral-transverse (FVT) anlagen independently formed for proter and opisthe, plus one or more short anlagen located between IV and V, which form surplus transverse cirri. Dorsal morphogenesis occurs as in typical oxytrichid dorsomarginalians, viz., with formation of three anlagen and fragmentation of the rightmost one. Dorsomarginal kineties are formed near anterior end of right marginal cirral row anlagen. Various anomalous specimens exhibiting more than two long ventral rows were found, which are explained by increasing the number of FVT anlagen and/or the number of cirri produced by anlagen. Comparative ontogeny and phylogenetic analyses based on the 18S rDNA reveal that Apoamphisiella vernalis is closely affine to North American and European strains of the Paraurostyla weissei complex. Their reduced genetic distances and conspicuous morphological variability show that both genera can overlap, which implies the necessity of re-evaluating the contextual relevance of some morphological characters commonly used for genus-level separation within hypotrich taxa.

Morphogenesis and Molecular Phylogeny of a New Freshwater Ciliate, Notohymena apoaustralis n. sp. (Ciliophora, Oxytrichidae)

The live morphology, infraciliature, and morphogenesis of a new oxytrichid ciliate, Notohymena apoaustralis n. sp. collected from a freshwater pond in Qingdao (Tsingtao), China, were studied in vivo and after protargol impregnation. Notohymena apoaustralis n. sp. is characterized as follows: undulating membranes in Notohymena-pattern; cortical granules yellow-green, grouped around the marginal cirri and dorsal bristles, and in short irregular rows elsewhere in the cell; single contractile vacuole positioned at anterior 1/3 of the body length; two macronuclear nodules and one micronucleus; about 39 adoral membranelles; 18 frontoventral transverse cirri in typical Oxytricha-pattern; one right and one left marginal row, almost confluent posteriorly; dorsal ciliature in typical Oxytricha-pattern; 8-10 caudal cirri arranged in three rows, one each at the posterior end of dorsal kineties 1, 2, and 4, indistinguishable from marginal cirri in life. The morphogenetic process in N. apoaustralis n. sp. is consistent with that of the type species, Notohymena rubescens Blatterer and Foissner, 1988. Phylogenetic analyses based on small subunit rDNA sequence data suggest a sister relationship between N. apoaustralis n. sp. and Paraurostyla weissei, which cluster in a clade with Rubrioxytricha ferruginea.

Evolution of Programmed DNA Rearrangements in a Scrambled Gene

Gene unscrambling in spirotrichous ciliates involves massive genome-wide DNA deletion and rearrangement events during development. During each sexual cycle, the somatic nucleus (macronucleus) regenerates from the germ line nucleus (micronucleus). Development of the polyploid somatic genome requires programmed DNA deletion of micronuclear-limited intragenic noncoding sequences and permutation and amplification of the protein-coding regions. Recent studies suggest that, despite novel insertions of endogenous transposon or foreign DNA into the germ line genome, ciliates possess a whole-genome surveillance system that guides the recapitulation of a functional somatic genome. This renders the germ line genome an extremely dynamic structure over evolutionary time. Here we describe the germ line and somatic architectures of the gene encoding alpha-telomere-binding protein in three early-diverging species (Holosticha sp., Uroleptus sp., and Paraurostyla weissei) and trace the natural history of DNA rearrangements in this gene in six species, including three previously studied oxytrichids. Comparisons of homologous coding regions between earlier and later diverging species provide evidence for fusion of scrambled germ line fragments as small as 24 bp during evolution, as well as simultaneous fragmentation and scrambling of the germ line locus and shifting of the boundaries between coding and noncoding DNA, leading to distinct gene architectures in each species. We infer an evolutionary recombination pathway that passes through identified intermediate species and gives rise to the observed patterns in all known species, capitalizing on their unique DNA rearrangement machinery and germ line flexibility.

Effect of the micronucleus on cellular structures in several hypotrichous ciliates

It is commonly believed that there is a sharp functional demarcation between the two types of nuclei of ciliated protozoa: the micronucleus for reorganization of the nuclear apparatus during sexual reproduction and the macronucleus for controlling somatic functions. This traditional view, however, has been critically re‐examined recently and correlative researches have shown that the micronucleus plays an essential role in the development of some ciliates. Here we report some morphological evidences about the effect of the micronucleus on cellular structures from amicronucleate cell lines of five hypotrichous ciliates (Pseudourostyla cristata, Pseudokeronopsis monilata, Paraurostyla weissei, Uroleptus piscis and Oxytricha faurei). All amicronucleate cell lines were generated by amputation and investigated by protargol staining. These observations manifest that micronucleus is indispensable to vigor and viability for P. weissei, to maintaining the integrity of adoral zone of membranelles (AZM) and/or undulating membranes (UM) for P. cristata, P. monilata and U. piscis, and to keeping regularity of cell shape as well as of the number and the structure of the macronuclei for O. faurei. These results suggest that the manifestations of the somatic function of micronucleus for different ciliates are varied and the close species might have a similar form of expression.This work was supported by a grant from NSFC (No: 30370210) to L. P. JIN.

Localization of Centrins in the Hypotrich Ciliate Paraurostyla weissei

Centrins are ubiquitous cytoskeletal proteins that are generally associated with the centrosome and form large cytoskeletal networks in protists. To obtain more data on the respective role of different centrin proteins, we studied their distribution and behavior in one ciliate species, Paraurostyla weissei, using specific antibodies. In this species, only two major proteins of 21 and 24 kDa corresponding to centrins, were identified by 1D and 2D electrophoresis. Immunofluorescence analysis showed that these two proteins displayed non-overlapping localization in the interphase cell and during morphogenesis. Both centrin proteins localize on the fibrous network linking the oral basal bodies in the interphase cell and in the form of marginal dots, which correspond to the proximal ends of the striated rootlets; the 21 kDa centrin was also detected within the basal bodies, whereas the 24 kDa centrin allowed identifying new structures, the frontal dashes. During morphogenesis, the 21 kDa centrin locates at the basal bodies, while the 24 kDa centrin is detected along the striated rootlets and in close association with the basal bodies pairs. These data are discussed in terms of the potential roles of the two centrins in different cellular functions.

Phylogenetic position of species in the genera Anoplophrya, Plagiotoma, and Nyctotheroides (Phylum Ciliophora), endosymbiotic ciliates of annelids and anurans.

We have used small subunit rRNA gene sequences to determine the phylogenetic relationships of species in three genera of endosymbiotic ciliates. We have confirmed that the astome Anoplophrya marylandensis is related to ciliates in the Class Oligohymenophorea, supporting the view that astomes are derived from hymenostome-like ancestors. We confirmed that Plaglotoma lumbrici, formerly considered to be a heterotrich, is a stichotrich spirotrich ciliate most closely related to Paraurostyla weissei in this analysis. Thus, the somatic polykinetids of Plagiotoma can be concluded to be cirri. We report the details of our isolation of Nyctotheroides deslierresae and Nyctotheroides parvus and confirm previous reports that these clevelandellids are related to the metopid and caenomorphid ciliates, now placed in the Class Armophorea.

A novel healing filament in ciliate regeneration.

The interphase cells of the hypotrich ciliate Paraurostyla weissei possess a complex fibrillar system surrounding basal bodies in the compound ciliary assemblages, cirri and membranelles. During replacement of the ciliature at cell division, transient filaments precede and accompany the development of ciliary primordia and participate in the formation of the fission furrow. Both fibrillar systems are recognized by monoclonal antibody FXXXIX 12G9. We studied regeneration of cellular fragments after transection employing the mAb 12G9 and found a new cytoskeletal structure involved in healing of the excisional wound. The healing filament is formed at the wound edge, distally and in connection with the bases of cirri closest to the wound. It is visible 5 min after transection. Concomitant with development of new ciliary primordia, the healing filament shrinks and finally disappears together with other transient fibers formed in this process. Ultrastructural analysis of immunolabeled regenerating cells revealed that structures recognized by mAb 12G9 contain fine filaments whose packing and arrangement depends on accompanying cytoplasmic elements and the developmental status of a fragment. Assembly of the healing fiber does not depend on microtubules and microfilaments since it develops in cellular fragments exposed to cold, nocodazole, and Cytochalasin D. On Western blots of whole cell and cytoskeletal extracts of P. weissei the 12G9 antibody identified one protein band whose molecular weight corresponds to 60 kDa.

Patterning of microtubule organizing centers during morphogenesis; Analysis in a ciliated protozoan, Paraurostyla weissei

Patterning of microtubule organizing centers during morphogenesis; Analysis in a ciliated protozoan, Paraurostyla weissei

Transmission of Surface Pattern Through a Dedifferentiated Stage in the Ciliate Paraurostyla. Evidence from the Analysis of Microtubule and Basal Body Deployment

ABSTRACT. During conjugation of the hypotrich ciliate Paraurostyla weissei, the two partners fuse to form a transient dedifferentiated stage, the zygocyst, which later redifferentiates into a vegetative cell. Immunocytochemical studies have been performed to follow the deployment of microtubules and basal bodies during the entire cycle of conjugation. They show that a superficial lattice persists during the whole zygocyst stage, after most of the infraciliature of the exconjugants has been disassembled. These superficial microtubules display different immunocytochemical properties in the mature zygocyst and during its morphogenesis, suggesting that some transient chemical modifications of the microtubules are associated with the morphogenetic activity. In the zygocyst, the superficial microtubules retain the specific orientation characteristic of the ventral and the dorsal sides of the recipient cell, respectively. In the course of subsequent morphogenesis of the zygocyst, these specific cellular territories differentiate into the ventral and dorsal sides of the new cell. Although our experiments do not resolve the question of whether superficial microtubules play an active or merely a passive role in the transmission of surface pattern, they show that no complete breakdown in cell polarity occurs, even through a profound dedifferentiated stage. Thus, the overall surface pattern appears to be retained, in a simplified form, through the conjugation cycle.

A Scaffold for Basal Body Patterning Revealed by a Monoclonal Antibody in the Hypotrich Ciliate Paraurostyla weissei

In the hypotrich ciliate Paraurostyla weisssi, the infraciliature consists of basal bodies on which cilia are anchored together with associated dense material and microtubular rootlets. This is renewed at each morphogenesis, which occurs both in the fully differentiated cell and in a transient dedifferentiated stage, the zygocyst. In both situations, the cell must reconstitute its typical ciliature by properly patterning its basal bodies. Insights into these morphogenetic processes were obtained through an immunocytochemical study using an antipericentriolar material antibody displaying remarkable properties. In Paraurostyla, this antibody decorates the electron-dense material associated with the basal bodies in the interphase cell (as it does with centrosomes on metazoan cells) but, during morphogenesis, the antibody decorates a transient system of tracks which appear prior ta basal body patterning and along which basal bodies will later be distributed. In all cases, tracks are initiated close to parental organelles and then elongate to form a system linking the anlagen together during their migration. During zygocyst morphogenesis, they extend along three main cellular meridians. As this antibody decorates an antigen associated with early steps of morphogenesis, it visualizes a proteinaceous system upstream to basal body patterning and provides a structural continuity between parental and newly assembled basal body systems.

Ultrastructural studies on the development of cortical structures in the ciliary pattern mutants of the hypotrich ciliate Paraurostyla weissei

We have studied the ultrastructure of interphase and developing cells of mutants (mlm and mlmlpl) of Paraurostyla weissei that overproduce basal bodies in certain cortical domains and bring about coordinate modifications of the overall pattern [8, 25, 26]. In interphase cells, basal bodies and accessory microtubular organelles appear normal. In developing cells, overgrowth of adorai primordia, multiplication of ciliary primordia, differentiation of dorsal bristles on the ventral surface, and reversal of the orientation of oral and cirral promordia occur in spite of apparently normal assembly events of all studied ciliary structures. The three kinds of basal body pairs (paroral, adorai and somatic) have the same ultrastructure as in wild-type cells. Abnormal orientation of pairs occurs during the first wave of basal body proliferation. In the second wave, the new basal bodies complete new cirri and membranelles regardless of their orientation. As in wt cells, there is no second wave of basal body proliferation in the paroral membranes. Early steps of elimination of one category of cirri (FC) involve small defects in basal body assembly during the first wave of basal body proliferation. Thus modifications in the ciliary pattern in the mlm/pl mutants result from overduplication, abnormal location and orientation of basal bodies taking place during the first half of the process of morphogenesis in this ciliate.

Domain-specific changes of ciliary striated rootlets during the cell cycle in the hypotrich ciliate Paraurostyla weissei

ABSTRACT The dynamics of striated ciliary rootlets (cr) during development of ciliary structures in cells of the hypotrich ciliate Paraurostyla weissei was studied by immunostaining with polyclonal antibody raised against isolated cr of Paramecium tetraurelia. Wildtype cells and two mutants: mlm showing multiple left marginal cirri and mlm/pl showing in addition a certain degree of pattern lability were used to study the boundaries of particular cortex domains. In interphase cells, cr are attached to all left marginal and caudal cirri and to only the posterior third of the right marginal cirri, cr appear in all nonoral primordia during the first wave of basal body proliferation. After nucleation and early elongation of cr, some cr undergo site-specific regression or stabilization. The spatial deployment of these different modes of development corresponds to specific cortical domains. In mlm/pl mutants, where specific cortical domains are broadened, changes in the cr system are characteristic for a given domain, regardless of its broadening, but boundaries between adjacent domains are weakened.

Natural and cultured variability of Engelmanniella mobilis (Ciliophora, Hypotrichida); with notes on the ultrastructure of its resting cyst

Summary The variability of 2 Austrian populations (Gn, Bn), one Turkish (Tn), and one Japanese population (Jn) of the hypotrich ciliate Engelmanniella mobilis ( Engelmann , 1862) Foissner , 1982 is compared by morphological and morphogenetic analyses. These populations were isolated from soils and represent 2 groups (Gn, Bn, Tn; Jn) concerning some quantitative characters of the infraciliature, the morphology of the resting cyst, and some nuclear features during division. However, in cultures maintained for 3 months the variability of the Turkish population (Tc) increased markedly closing this gap. This demonstrates that morphological differences originating during cultivation might be greater than those observed in natural populations. The variability of our populations embraces E. halseyi ( Calkins , 1929) and E. mobilis americanus ( Kahl , 1932), which thus fall as junior synonyms of E. mobilis . During division and physiological reorganization the cortical events are identical in all populations, while the micronuclear processes may be slightly modified. Divisional and reorganizational morphogenesis differ in the origin of the frontal anlagen. The characterization of Engelmanniella Foissner , 1982 is improved. Young resting cysts of Bn, Tn, and Tc are characterized by a mucus layer originating from the extruded subpellicular granules. This layer is absent in older cysts and in the resting cyst of the Japanese population, although the subpellicular granules are released too. Oxytrichid (4-layered cyst wall, fused macronuclear segments) and urostylid (cortical microtubules) characters are mixed up in the resting cyst of E. mobilis, Kahliella simplex , and Paraurostyla weissei suggesting that the proposed classification of hypotrich resting cysts is premature.

Defective spatial control in patterning of microtubular structures in mutants of the ciliate Paraurostyla: II. Spatial coordinates in a double recessive mutant

The abnormal ciliary pattern and its propagation was studied in the double recessive mutant 95 (mlm/mlm, pl/pl) in Paraurostyla weissei. In line 95, widening and concomitant overlapping of three organelle domains occurs at the right ventro-lateral part of the cell, in addition to the multi-left-marginal syndrome involving broadening of three organellar domains in the left ventro-lateral part of the cell (Dubielecka and Jerka-Dziadosz 1989). The modifications in positioning of ciliary primordia pervade both left and right parts of the cell, suggesting that the cell's ability to maintain discrete boundary conditions is affected. The way in which particular primordia of ciliature develop is consistent with an intercalation-overlapping model that postulates a cyclic instability of the system of positional information caused by a change in distribution of the ventral positional values and intercalation of intermediate values at the lateral parts of the cell. The developmental phenotype is a result of the ability of the morphogenetic machinery of the cell to record different phases of the postulated positional cycle.

Encystment in the Hypotrichous Ciliate Paraurostyla weissei: Ultrastructure and Cytochemistry1

ABSTRACTThe cyst wall of Paraurostyla weissei consists of four morphologically distinct layers. It shows an ultrastructure and composition similar to that of the previously described kinetosome‐resorbing cysts, and its cytoplasm displays characteristics of “urostylid‐type” cysts. Therefore it is possible to consider it a “transition ciliate” between Stichotrichina and Sporadotrichina.

Mirror-image configuration of the cortical pattern causes modifications in propagation of microtubular structures in the hypotrich ciliateParaurostyla weissei

Analysis or the development of microtubular structures in the mirror-image doublet cell lines of a hypotrich ciliate,Paraurostyla weissei, revealed several modifications in standard morphogenesis. Ciliary primordia can be formed without prior disaggregation of the preformed marginal cirri, on the left instead of the right hand side of an old row. Two or more overlapping streak segments may originate from disaggregating old marginal cirri, giving rise to two or three cirral rows. Inverted marginal cirri occasionally develop de novo and can be propagated clonally. Thus the modifications in developmental processes concern the positioning of primordia, the number of forming structures and the polarity of these structures. The microtubular triplets in the basal bodies of normal and inverted cirri do not differ, indicating that the large-scale reversal of the overall pattern has no effect on the assembly of microtubular triplets. The study indicates that the control of cytotactic propagation of compound microtubular structures is either modified or partially suppressed in a morphogenetic field where the positional values along one of the main cellular axes (lateral) have been reversed.