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1.
N. B. Matveeva V. A. Teplov A. R. Nezvetsky T. G. Orlova S. I. Beylina 《Biophysics》2012,57(5):644-650
Possible involvement of autocrine factors into the control of motile behavior via a receptor-mediated mechanism was investigated in Physarum polycephalum plasmodium, a multinuclear amoeboid cell with the auto-oscillatory mode of motility. Cyclic adenosine monophosphate (cAMP) and extracellular cAMP-specific phosphodiesterase, its involvement into the control of plasmodium motile behavior was proved by action of its strong inhibitor, were regarded as putative autocrine factors. It was shown that the plasmodium secreted cAMP. When it was introduced into agar support, 0.1–1 mM cAMP induced a delay of the plasmodium spreading and its transition to migration. When locally applied, cAMP at the same concentrations induced the typical for attractant action increase in oscillation frequency and the decrease of ectoplasm elasticity. The ability to exhibit positive chemotaxis in cAMP gradient and the dependence of its realization were shown to depend on the plasmodium state. Chemotaxis test specimens obtained from the migrating plasmodium, unlike those obtained from growing culture, generate alternative fronts which compete effectively with fronts oriented towards the attractant increment. The results obtained support our supposition stated earlier that advance of the Physarum polycephalum plasmodium leading edge is determined by local extracellular cAMP gradients arising from a time delay between secretion and hydrolysis of the nucleotide. 相似文献
2.
During the last stage of Dictyostelium development a motile, cylindrical slug transforms into an immotile, stalked fruiting body and the constituent cells change from amoebae to either refractile spores or vacuolated stalk cells. Analysis of this process using genetics and simple culture techniques is becoming a powerful way of investigating a number of conserved signal transduction processes. A common pathway activating cAMP-dependent protein kinase (PKA) triggers the maturation of spore cells and those stalk cells forming the stalk. It uses a eukaryotic version of the 'bacterial' two-component phospho-relay system to control cAMP breakdown. A second pathway, inhibiting the GSK3 protein kinase, might control the maturation of a distinct set of stalk cells at the base of the fruiting body. 相似文献
3.
Possible involvement of extracellular cAMP-specific phosphodiesterase in the control of cell motile behavior has been investigated in Physarum polycephalum plasmodium, a multinuclear amoeboid cell with the autooscillatory mode of motility. It was found that the rate of the hydrolysis of 10 mM cAMP by a partially purified preparation of cAMP-specific phosphodiesterase secreted by the plasmodium in the course of migration decreases 20-30 times under the action of 1 mM dithiothreitol. In the presence of 1-5 mM of this strong reducing agent, the onset of the plasmodium spreading and the transition to the stage of migration were delayed in a concentration-dependent manner. In accordance with the morphological pattern of motile behavior, the duration of the maintenance of high frequency autooscillations, which normally precede the increase in the rate of the spreading and appear also in response to the application of attractants at spatially uniform concentrations, strongly increased by the action of dithiothreitol. The results obtained suggest that the autocrine production of cAMP and extracellular cAMP-specific phosphodiesterase is an important constituent of the mechanism controlling the motile behavior of the Physarum polycephalum plasmodium. 相似文献
4.
An obligate intracellular parasite infecting Ectocarpus spp. and other filamentous marine brown algae is described. The pathogen forms an unwalled multinucleate syncytium (plasmodium) within the host cell cytoplasm and causes hypertrophy. Cruciform nuclear divisions occur during early development. Mature plasmodia become transformed into single sporangia, filling the host cell completely, and then cleave into several hundred spores. The spores are motile with two unequal, whiplash-type flagella inserted subapically and also show amoeboid movement. Upon settlement, cysts with chitinous walls are formed. Infection of host cells is accomplished by means of an adhesorium and a stachel apparatus penetrating the host cell wall, and injection of the cyst content into the host cell cytoplasm. The parasite is characterized by features specific for the plasmodiophorids and is described as a new genus and species, Maullinia ectocarpii. 相似文献
5.
N. B. Matveeva M. A. Morozov A. R. Nezvetsky T. G. Orlova V. A. Teplov S. I. Beylina 《Biophysics》2010,55(6):982-986
Possible involvement of extracellular cAMP-specific phosphodiesterase in the control of cell motile behavior has been investigated
in Physarum polycephalum plasmodium, a multinuclear amoeboid cell with the autooscillatory mode of motility. It was found that the rate of the hydrolysis
of 10 mM cAMP by a partially purified preparation of cAMP-specific phosphodiesterase secreted by the plasmodium in the course
of migration decreases 20–30 times under the action of 1 mM dithiothreitol. In the presence of 1–5 mM of this strong reducing
agent, the onset of the plasmodium spreading and the transition to the stage of migration were delayed in a concentration-dependent
manner. In accordance with the morphological pattern of motile behavior, the duration of the maintenance of high frequency
autooscillations, which normally precede the increase in the rate of the spreading and appear also in response to the application
of attractants at spatially uniform concentrations, strongly increased by the action of dithiothreitol. The results obtained
suggest that the autocrine production of cAMP and extracellular cAMP-specific phosphodiesterase is an important constituent
of the mechanism controlling the motile behavior of the Physarum polycephalum plasmodium. 相似文献
6.
An obligate intracellular parasite infecting Ectocarpus spp. and other filamentous marine brown algae is described. The pathogen forms an unwalled multinucleate syncytium (plasmodium) within the host cell cytoplasm and causes hypertrophy. Cruciform nuclear divisions occur during early development. Mature plasmodia become transformed into single sporangia, filling the host cell completely, and then cleave into several hundred spores. The spores are motile with two unequal, whiplash-type flagella inserted subapically and also show amoeboid movement. Upon settlement, cysts with chitinous walls are formed. Infection of host cells is accomplished by means of an adhesorium and a stachel apparatus penetrating the host cell wall, and injection of the cyst content into the host cell cytoplasm. The parasite is characterized by features specific for the plasmodiophorids and is described as a new genus and species, Maullinia ectocarpii. 相似文献
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8.
Eugene W. Crawford Lawrence J. Shimkets 《BioEssays : news and reviews in molecular, cellular and developmental biology》1994,16(3):161-163
Intercellular signaling plays an important role in spatially regulated developmental processes. Myxococcus xanthus C signal transmission during fruiting body formation requires motile, densely packed, well aligned cells. tThe fruiting body consists of two domains: an outer domain which has densely packed, well aligned, motile cells: and an inner domain of more loosely packed, non-motile, sporulating cells. The two domains are characterized by different patterns of C-dependent gene expression, which begins in the outer domain where C-signaling is most efficient, and reaches its maximum in the inner domain. These domains may be maintained by a dynamic mechanism which relies on passive transport of the sporulating cells from the outer domain, where sporulation is initiated, to the inner domain by the motile cells in the outer domain. 相似文献
9.
John Sternfeld 《Development genes and evolution》1998,208(9):487-494
Shortly after initiation of Dictyostelium fruiting body formation, prespore cells begin to differentiate into non-motile spores. Although these cells lose their ability
to move, they are, nevertheless, elevated to the tip of the stalk. Removal of the amoeboid anterior-like cells, located above
the differentiating spores in the developing fruiting body, prevents further spore elevation although the stalk continues
to elongate. Furthermore, replacement of the anterior-like cells with anterior-like cells from another fruiting body largely
restores the ability to lift the spores to the top of the stalk. However, if amoeboid prestalk cells are used to replace the
anterior-like cells, there is no restoration of spore elevation. Finally, when a droplet of mineral oil replaces differentiating
spores, it is treated as are the spores: the mineral oil is elevated in the presence of anterior-like cells and becomes arrested
on the stalk in the absence of anterior-like cells. Because a similar droplet of mineral oil is totally ignored by slug tissue,
it appears that there is a dramatic transformation in the treatment of non-motile matter at this point in Dictyostelium development.
Received: 26 January 1998 / Accepted: 27 May 1998 相似文献
10.
Multicellular development in Myxococcus xanthus is stimulated by predator-prey interactions 下载免费PDF全文
Myxococcus xanthus is a predatory bacterium that exhibits complex social behavior. The most pronounced behavior is the aggregation of cells into raised fruiting body structures in which cells differentiate into stress-resistant spores. In the laboratory, monocultures of M. xanthus at a very high density will reproducibly induce hundreds of randomly localized fruiting bodies when exposed to low nutrient availability and a solid surface. In this report, we analyze how M. xanthus fruiting body development proceeds in a coculture with suitable prey. Our analysis indicates that when prey bacteria are provided as a nutrient source, fruiting body aggregation is more organized, such that fruiting bodies form specifically after a step-down or loss of prey availability, whereas a step-up in prey availability inhibits fruiting body formation. This localization of aggregates occurs independently of the basal nutrient levels tested, indicating that starvation is not required for this process. Analysis of early developmental signaling relA and asgD mutants indicates that they are capable of forming fruiting body aggregates in the presence of prey, demonstrating that the stringent response and A-signal production are surprisingly not required for the initiation of fruiting behavior. However, these strains are still defective in differentiating to spores. We conclude that fruiting body formation does not occur exclusively in response to starvation and propose an alternative model in which multicellular development is driven by the interactions between M. xanthus cells and their cognate prey. 相似文献
11.
Cellular slime molds (CSMs) possess a remarkable life cycle that encompasses an extreme act of altruism. CSM cells live as individual amoebae until starved, then aggregate and ultimately transform themselves into a multicellular fruiting body. This fruiting body consists of stalk cells (altruists that eventually die) and spores (the beneficiaries of this sacrifice). Altruistic systems such as this are vulnerable to cheaters, which are individuals unrelated to the altruists that obtain the benefits provided by them without reciprocating. Here, we investigate two forces that can maintain CSM altruism despite cheating: kin selection and anticheater adaptations. First, we present new kinship-based models based on CSM developmental biology to evaluate the efficacy of kin selection. These models show that stalk-making genotypes can still be maintained when aggregations are initiated by multiple "founder" spores, provided that spores of stalkless fruiting bodies have low rates of dispersal and dispersal success is a concave function of stalk height. Second, we review proposals that several features of CSM development, such as the chemical suppression of the redifferentiation of prestalk cells into prespores, act as anticheater adaptations. 相似文献
12.
Using a phase-locked mutant of Myxococcus xanthus to study the role of phase variation in development. 总被引:1,自引:0,他引:1 下载免费PDF全文
The bacterium Myxococcus xanthus undergoes a primitive developmental cycle in response to nutrient deprivation. The cells aggregate to form fruiting bodies in which a portion of the cells differentiate into environmentally resistant myxospores. During the growth portion of the M. xanthus life cycle, the organism also undergoes a phase variation, in which cells alternate between yellow and tan colony-forming variants. Phase variation occurs in our laboratory strain (M102, a derivative of DK1622) at a frequency high enough that a single colony of either the yellow or the tan phase already contains cells of the alternate phase. In this study we demonstrate that tan cells within a predominantly yellow population of phase variation-proficient cells are preferentially recovered as heat- and sonication-resistant spores. To further investigate the possibility of a differential role of tan and yellow cells during development, a tan-phase-locked mutant was used to compare the developmental phenotypes of a pure tan population with a predominantly yellow, phase variation-proficient population. Pure tan-phase populations did not produce fruiting bodies or mature spores under conditions in which predominantly yellow wild-type populations did so efficiently. Pure populations of tan-phase cells responded to developmental induction by changing from vegetative rod-shaped cells to round forms but were unable to complete the maturation to heat- and sonication-resistant, refractile spores. The developmental defect of a tan-phase-locked mutant was rescued by the addition of phase variation-proficient cells from a predominantly yellow culture. In such mixtures the tan-phase-locked mutant not only completed the process of forming spores but also was again preferentially represented among the viable spores. These findings suggest the intriguing possibility that the tan-phase cells within the vegetative population entering development are the progenitors of spores and implicate a requirement for yellow-phase cells in spore maturation. 相似文献
13.
CARLOS E. LANGE CHARLES M. MACVEAN JOHN E. HENRY DOUGLAS A. STREETT 《The Journal of eukaryotic microbiology》1995,42(5):552-558
ABSTRACT. Heterovesicula cowani , n. g., n. sp., is a dimorphic microsporidium described from the adipose tissue of the Mormon cricket, Anabrus simplex Haldeman. Proliferation of the microsporidium is by karyokinesis of uninucleate and binucleate cells to form binucleate and tetranucleate cells, respectively. These cells will undergo binary fission (merogony). Ultimately, the meronts undergo karyokinesis without subsequent cytokinesis producing spherical multinucleate plasmodia that are transitional to 2 types of sporogony. Transitional to disporoblastic sporogony, a fragile interfacial envelope delaminates from the plasmodium with morphogenesis to a monfiliform plasmodium consisting of fusiform binucleate diplokaryotic sporonts. These undergo karyokinesis to form tetranucleate diplokaryotic sporonts that undergo cytokinesis during disintegration of the plasmodium into isolated binucleate sporonts. Transitional to octosporoblastic sporogony, multinucleate plasmodia disintegrate into short monofiliform plasmodia of diplokaryotic sporonts which then segregate while undergoing gradual nuclear dissociation (haplosis by nuclear dissociation). These undergo two sequences of karyokinesis and subsequent multiple fission to form eight uninucleate (haploid) sporoblasts in a fusiform arrangement within a persistent envelope. Binucleate spores are ovocylindrical, about 5.4 × 1.7 μm (fresh), with an isofilar polar filament singly coiled about 11 turns. Uninucleate spores are ovoid to slightly pyriform, 4.0 × 1.7 μm (fresh), with an isofilar filament singly coiled about 9 turns. A new family, Heterovesculidae, is proposed for the new genus. 相似文献
14.
The usual sequence of forms in the Physarum polycephalum life cycle is plasmodium-spore-amoeba-plasmodium. So-called "amoebaless life cycle" or alc mutants of this Myxomycete undergo a simplified plasmodium-spore-plasmodium life cycle. We have analyzed three independently isolated alc mutants and found in each case that the failure of the spores to give rise to amoebae is due to a recessive Mendelian allele. The three mutations are tightly linked to one another and belong to a single complementation group, alcA. The mutations are pleiotropic, not only interfering with the establishment of the amoebal form at spore germination, but also affecting the phenotype of alc amoebae, which occasionally arise from alc spores. The alc amoebae (1) grow more slowly than wild type, particularly at elevated temperatures; (2) tend to transform directly into plasmodia, circumventing the sexual fusion of amoebae that usually accompanies plasmodium formation; and (3) form plasmodia by the sexual mechanism less efficiently than wild-type amoebae. The various effects of an alc mutation seem to derive from mutation of a single gene, since reversion for one effect is always accompanied by reversion for the other effects. Moreover, a mutation, aptA1, that blocks direct plasmodium formation by alcA amoebae, also increases their growth rate to near normal. The manner of plasmodium formation in alcA strains differs significantly from that in another class of mutants, the gad mutants. Unlike gad amoebae, alcA amoebae need not reach a critical density in order to differentiate directly into plasmodia and do not respond to the extracellular inducer of differentiation. In addition, alcA differentiation is not prevented by a mutation, npfA1, that blocks direct differentiation by most gad amoebae. 相似文献
15.
Ronny Larsson 《Journal of invertebrate pathology》1983,42(3):348-356
Hyalinocysta expilatoria n. sp. is described from a larva of Odagmia ornata collected in Sweden. Infection was restricted to the adipose tissue which was transformed into a syncytium. The earliest stage observed was diplokaryotic merozoites, which mature directly into diplokaryotic sporonts. Each sporont produces a sporophorous vesicle (pansporoblast), which persists, also enclosing mature spores. Usually nuclear divisions result in a plasmodium with 8 nuclei, which fragments into 8 sporoblasts, each of which develops into a spore without further division. Occasionally an aberrant number of spores (2, 4, 6) is formed. The spores are pyriform with a flattened area at the posterior pole. Spores in sporophorous vesicles with 8 spores are 4.0–6.0 μm long, in vesicles with 4 spores 4.0–5.0 μm, and in vesicles with 2 spores 7.0–8.0 μm. In some vesicles the spores develop asynchronously, and 2, 4, or 6 mature spores are found together with 6, 4, or 2 immature. There was also a small number of vesicles with supernumerary spores, less than 8 normally developed. The 325–350 nm thick spore wall is composed of three layers. The polar filament is anisofilar with 7 coils in a single layer. The anterior 5–6 coils are wide, the posterior 2-1 thin. The angle of tilt of the anterior filament coil is approximately 50°. The spore has a single nucleus. The sporophorous vesicle is delimited by a thin membrane, also visible in haematoxylin stained preparations. Vesicles with mature spores are void of metabolic inclusions. 相似文献
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18.
The plasmodium of Badhamia alpina thrived at lower temperatures (4 °C), and formed fruiting bodies at 8 °C. The yellow sclerotium and plasmodium were found inside a hollow, dead herbaceous stem under melting snow in Apr, and was cultured in moist chambers at 4 °C. The plasmodium did not form fruiting bodies for 6 wk at 4 °C. Sporulation was observed after the incubation temperatures rose to 8 °C. Sporulation occurred in the morning and cell cleavage at 11 a.m. The order of spore wall formation was observed by TEM for 12 h. The outer spore wall ornamentation was formed first followed by internal wall layers. Round electron transparent object was observed in the capillitium and peridium during the latter part of sporulation. 相似文献
19.
Myxomycetes are also called plasmodial slime molds, due to one of their characteristic features, the occurrence of the plasmodium. However, most of the distinguishing characters of the five orders currently recognised are based on the morphology of fruiting bodies and spores. Although a few myxomycetes have become widely used model organisms for genetic and cytological studies, complete information relating to the number of chromosomes in haploid cells (n) is lacking thus far. Only two species of the order Physarales have been examined with respect to chromosome numbers. Here, we present a complete data set on the numbers of chromosomes in ten species of myxomycetes that are members of all five orders. Our analysis indicates that n?=?21 is the evolutionary ancient chromosome number that occurs in the morphologically simple orders Liceales and Ceratiomyxales. More derived taxa, such as the Physarales, have significantly higher chromosome numbers (n?=?30). These data shed light on the phylogenetic relationships within the myxomycetes. 相似文献