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Bastiaan Willem Ibelings - One of the best experts on this subject based on the ideXlab platform.
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Temperature Alters Host Genotype-Specific Susceptibility to Chytrid Infection
2016Co-Authors: Alena S, Lisette N. De Senerpont Domis, Alena S. Gsell, Ellen Van Donk, Bastiaan Willem IbelingsAbstract:The cost of parasitism often depends on environmental conditions and host identity. Therefore, variation in the biotic and abiotic environment can have repercussions on both, species-level host-parasite interaction patterns but also on host genotype-specific susceptibility to disease. We exposed seven genetically different but concurrent strains of the diatom Asterionella formosa to one genotype of its naturally co-occurring chytrid parasite Zygorhizidium planktonicum across five environmentally relevant temperatures. We found that the thermal tolerance range of the tested parasite genotype was narrower than that of its host, providing the host with a "cold " and "hot " thermal refuge of very low or no infection. Susceptibility to disease was host genotype-specific and varied with temperature level so that no genotype was most or least resistant across all temperatures. This suggests a role of thermal variation in the maintenance of diversity in disease related traits in this phytoplankton host. The duration and intensity of chytrid parasite pressure on host populations is likely to be affected by the projected changes in [...] GSELL, Alena S, et al. Temperature Alters Host Genotype-Specific Susceptibility to Chytri
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Hidden diversity in the freshwater planktonic diatom Asterionella formosa.
Molecular ecology, 2015Co-Authors: Silke Van Den Wyngaert, Bastiaan Willem Ibelings, Markus Möst, Remo Freimann, Piet SpaakAbstract:Many freshwater and marine algal species are described as having cosmopolitan distributions. Whether these widely distributed morphologically similar algae also share a similar gene pool remains often unclear. In the context of island biogeography theory, stronger spatial isolation deemed typical of freshwater lakes should restrict gene flow and lead to higher genetic differentiation among lakes. Using nine microsatellite loci, we investigate the genetic diversity of a widely distributed freshwater planktonic diatom, Asterionella formosa, across different lakes in Switzerland and the Netherlands. We applied a hierarchical spatial sampling design to determine the geographical scale at which populations are structured. A subset of the isolates was additionally analysed using amplified fragment length polymorphism (AFLP) markers. Our results revealed complex and unexpected population structure in A. formosa with evidence for both restricted and moderate to high gene flow at the same time. Different genetic markers (microsatellites and AFLPs) analysed with a variety of multivariate methods consistently revealed that genetic differentiation within lakes was much stronger than among lakes, indicating the presence of cryptic species within A. formosa. We conclude that the hidden diversity found in this study is expected to have implications for the further use of A. formosa in biogeographical, conservation and ecological studies. Further research using species-level phylogenetic markers is necessary to place the observed differentiation in an evolutionary context of speciation.
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Thermal tolerance ranges of aggregated, species-level measures of host and parasite productivity across temperature environments.
2013Co-Authors: Alena S. Gsell, Lisette N. De Senerpont Domis, Ellen Van Donk, Bastiaan Willem IbelingsAbstract:This plot shows overall thermal reaction norms of exposed, but uninfected (light grey) and exposed, infected (dark grey) host (expressed as a rate of change day–1 in Asterionella cells) separately and combined (no colour), as well as the thermal reaction norm of the parasite (as rate of change day–1 of chytrid sporangia, black bars) in experimental units. The thermal tolerance range of the tested parasite genotype is narrower than that of the host as the parasite population shows low or no growth at both temperature extremes while the host population is still productive.
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genotype by temperature interactions may help to maintain clonal diversity in Asterionella formosa bacillariophyceae
Journal of Phycology, 2012Co-Authors: Alena S. Gsell, Lisette N. De Senerpont Domis, Wolf M. Mooij, Ellen Van Donk, Anna Przytulskabartosiewicz, Bastiaan Willem IbelingsAbstract:Marine and freshwater phytoplankton populations often show large clonal diversity, which is in disagreement with clonal selection of the most vigorous genotype(s). Temporal fluctuation in selection pressures in variable environments is a leading explanation for maintenance of such genetic diversity. To test the influence of temperature as a selection force in continually (seasonally) changing aquatic systems we carried out reaction norms experiments on co-occurring clonal genotypes of a ubiquitous diatom species, Asterionella formosa Hassall, across an environmentally relevant range of temperatures. We report within population genetic diversity and extensive diversity in genotype-specific reaction norms in growth rates and cell size traits. Our results showed genotype by environment interactions, indicating that no genotype could outgrow all others across all temperature environments. Subsequently, we constructed a model to simulate the relative proportion of each genotype in a hypothetical population based on genotype and temperature-specific population growth rates. This model was run with different seasonal temperature patterns. Our modeling exercise showed a succession of two to several genotypes becoming numerically dominant depending on the underlying temperature pattern. The results suggest that (temperature) context dependent fitness may contribute to the maintenance of genetic diversity in isolated populations of clonally reproducing microorganisms in temporally variable environments.
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host parasite interactions between freshwater phytoplankton and chytrid fungi chytridiomycota
Journal of Phycology, 2004Co-Authors: Bastiaan Willem Ibelings, Maiko Kagami, M Rijkeboer, Michaela Brehm, Arnout De Bruin, Ellen Van DonkAbstract:Some chytrids are host-specific parasiticfungithat may have a considerable impact on phytoplankton dynamics. The phylum Chytridiomycota contains one class, the Chytridiomycetes, and is composed of five different orders. Molecular studies now firmly place the Chytridiomycota within the fungal kingdom. Chytrids are characterized by having zoospores, a motile stage in their life cycle. Zoospores are attracted to the host cell by specific signals. No single physical-chemical factor has been found that fully explains the dynamics of chytrid epidemics in the field. Fungal periodicity was primarily related to host cell density. The absence of aggregated distributions of chytrids on their hosts suggested that their hosts did not vary in their susceptibility to infection. A parasite can only become epidemic when it grows faster than the host. Therefore, it has been suggested that epidemics in phytoplankton populations arise when growth conditions for the host are unfavorable. No support for such a generalization was found, however. Growth of the parasitic fungus Rhizophydium planktonicum Canter emend, parasitic on the diatom Asterionella formosa Hassal, was reduced under stringent nutrient limitation,because production and infectivity of zoospores were affected negatively. A moderate phosphorous or light limitation favored epidemic development, however. Chytrid infections have been shown to affect competition between their algal hosts and in this way altered phytoplankton succession. There is potential for coevolution between Asterionella and the chytrid Zygorhizidium planktonicum Canter based on clear reciprocal fitness costs, absence of overall infective parasite strains, and possibly a genetic basis for host susceptibility and parasite infectivity. [KEYWORDS: chytrids ; coevolution ; diatoms ; epidemics ; food webs ; hosts; parasites; phytoplankton; succession; zoospores]
Gontero Brigitte - One of the best experts on this subject based on the ideXlab platform.
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Inorganic carbon uptake in a freshwater diatom, Asterionella formosa (Bacillariophyceae): from ecology to genomics
'Informa UK Limited', 2021Co-Authors: Maberly Stephen, Villain Adrien, Puppo Carine, Gontero Brigitte, Severi Ilenia, Giordano MarioAbstract:International audienceInorganic carbon availability can limit primary productivity and control species composition of freshwater phytoplankton. This is despite the presence of CO2-concentrating mechanisms (CCMs) in some species that maximize inorganic carbon uptake. We investigated the effects of inorganic carbon on the seasonal distribution, growth rates and photosynthesis of a freshwater diatom, Asterionella formosa, and the nature of its CCM using genomics. In a productive lake, the frequency of A. formosa declined with CO2 concentration below air-equilibrium. In contrast, CO2 concentrations at 2.5-times air-equilibrium did not increase growth rate, cell C-quota or the ability to remove inorganic carbon. A pH-drift experiment strongly suggested that HCO3− as well as CO2 could be used. Calculations combining hourly inorganic carbon concentrations in a lake with known CO2 and HCO3− uptake kinetics suggested that rates of photosynthesis of A. formosa would be approximately carbon saturated and largely dependent on CO2 uptake when CO2 was at or above air-equilibrium. However, during summer carbon depletion, HCO3− would be the major form of carbon taken up and carbon saturation will fall to around 30%. Genes encoding proteins involved in CCMs were identified in the nuclear genome of A. formosa. We found carbonic anhydrases from subclasses α, β, γ and θ, as well as solute carriers from families 4 and 26 involved in HCO3− transport, but no periplasmic carbonic anhydrase. A model of the components of the CCM and their location in A. formosa showed that they are more similar to Phaeodactylum tricornutum than to Thalassiosira pseudonana, two marine diatoms
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Inorganic carbon uptake in a freshwater diatom, Asterionella formosa (Bacillariophyceae): from ecology to genomics
'Informa UK Limited', 2021Co-Authors: Maberly, Stephen C., Villain Adrien, Puppo Carine, Gontero Brigitte, Severi Ilenia, Giordano MarioAbstract:Inorganic carbon availability can limit primary productivity and control species composition of freshwater phytoplankton. This is despite the presence of CO2-concentrating mechanisms (CCMs) in some species that maximize inorganic carbon uptake. We investigated the effects of inorganic carbon on the seasonal distribution, growth rates and photosynthesis of a freshwater diatom, Asterionella formosa, and the nature of its CCM using genomics. In a productive lake, the frequency of A. formosa declined with CO2 concentration below air-equilibrium. In contrast, CO2 concentrations at 2.5-times air-equilibrium did not increase growth rate, cell C-quota or the ability to remove inorganic carbon. A pH-drift experiment strongly suggested that HCO3− as well as CO2 could be used. Calculations combining hourly inorganic carbon concentrations in a lake with known CO2 and HCO3− uptake kinetics suggested that rates of photosynthesis of A. formosa would be approximately carbon saturated and largely dependent on CO2 uptake when CO2 was at or above air-equilibrium. However, during summer carbon depletion, HCO3− would be the major form of carbon taken up and carbon saturation will fall to around 30%. Genes encoding proteins involved in CCMs were identified in the nuclear genome of A. formosa. We found carbonic anhydrases from subclasses α, β, γ and θ, as well as solute carriers from families 4 and 26 involved in HCO3− transport, but no periplasmic carbonic anhydrase. A model of the components of the CCM and their location in A. formosa showed that they are more similar to Phaeodactylum tricornutum than to Thalassiosira pseudonana, two marine diatoms
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Complete mitochondrial genome sequence of the freshwater diatom Asterionella formosa
'Informa UK Limited', 2017Co-Authors: Villain Adrien, Kojadinovic Mila, Puppo Carine, Prioretti Laura, Hubert Pierre, Grégori Gérald, Roulet Alain, Roques Céline, Claverie Jean-michel, Gontero BrigitteAbstract:International audienceWe report the complete mitochondrial genome sequence of the freshwater diatom Asterionella formosa. The large 61.9 kb circular sequence encodes 34 proteins and 25 tRNAs that are universally conserved in other sequenced diatoms. We fully resolved a unique 24 kb region containing highly conserved repeated sequence units, possibly collocating with an origin of replicatio
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Glyceraldehyde-3-phosphate dehydrogenase is regulated by ferredoxin-NADP reductase in the diatom Asterionella formosa
'Wiley', 2014Co-Authors: Mekhalfi Malika, Puppo Carine, Avilan Luisana, Lebrun Regine, Mansuelle Pascal, Maberly, Stephen C., Gontero BrigitteAbstract:Diatoms are a widespread and ecologically important group of heterokont algae that contribute about 20% to global productivity. Previous work has shown that regulation of key Calvin cycle enzymes in diatoms differs from that of the Plantae, and that in crude extracts, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) can be inhibited by NADPH under oxidizing conditions. Here, chromatography, mass spectrometry and sequence analysis showed that in the freshwater diatom, Asterionella formosa, GAPDH can interact with ferredoxin-NADP reductase (FNR) from the primary phase of photosynthesis, and the small chloroplast protein, CP12. In contrast, the ternary complex between GAPDH, phosphoribulokinase (PRK) and CP12, that is widespread in Plantae and cyanobacteria, was absent. Surface plasmon resonance measurements confirmed that GAPDH and FNR are able to interact. Activity measurements under oxidizing conditions, showed that NADPH can inhibit GAPDH-CP12 in the presence of FNR from A. formosa or Spinacia oleracea, explaining the earlier observed inhibition within crude extracts. Diatom plastids have distinctive attributes including the lack of the oxidative pentose phosphate pathway and so cannot produce NADPH in the dark. The observed down-regulation of GAPDH may allow NADPH to be re-routed towards other reductive processes contributing to their ecological success
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Glyceraldehyde-3-phosphate dehydrogenase is regulated by ferredoxin-NADP reductase in the diatom Asterionella formosa
'Wiley', 2014Co-Authors: Mekhalfi Malika, Puppo Carine, Avilan Luisana, Lebrun Regine, Mansuelle Pascal, Maberly, Stephen C., Gontero BrigitteAbstract:International audienceDiatoms are a widespread and ecologically important group of heterokont algae that contribute c. 20% to global productivity. Previous work has shown that regulation of their key Calvin cycle enzymes differs from that of the Plantae, and that in crude extracts, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) can be inhibited by nicotinamide adenine dinucleotide phosphate reduced (NADPH) under oxidizing conditions. The freshwater diatom, Asterionella formosa, was studied using enzyme kinetics, chromatography, surface plasmon resonance, mass spectrometry and sequence analysis to determine the mechanism behind this GAPDH inhibition. GAPDH interacted with ferredoxin–nicotinamide adenine dinucleotide phosphate (NADP) reductase (FNR) from the primary phase of photosynthesis, and the small chloroplast protein, CP12. Sequences of copurified GAPDH and FNR were highly homologous with published sequences. However, the widespread ternary complex among GAPDH, phosphoribulokinase and CP12 was absent. Activity measurements under oxidizing conditions showed that NADPH can inhibit GAPDH-CP12 in the presence of FNR, explaining the earlier observed inhibition within crude extracts. Diatom plastids have a distinctive metabolism, including the lack of the oxidative pentose phosphate pathway, and so cannot produce NADPH in the dark. The observed down-regulation of GAPDH in the dark may allow NADPH to be rerouted towards other reductive processes contributing to their ecological success
Arlette Cazaubon - One of the best experts on this subject based on the ideXlab platform.
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fungal parasitism of the diatom Asterionella formosa hassall bacillariophyceae by chytridiomycota
Annales De Limnologie-international Journal of Limnology, 2004Co-Authors: Celine Bertrand, Alain Couté, Arlette CazaubonAbstract:Many freshwater algae are parasitized by aquatic fungi belonging to the Chytridiales Order. The top-down effects of parasitism result in individual losses within algal populations. We present data on the parasitism of the diatom Asterionella formosa Hassall by chytrids, occurring in response to hydrodynamic disturbances and the architecture of the algal host on the landscape scale. Among a series of nine reservoirs, the observed pattern of parasitism depends on the levels of hydrodynamic disturbance: the rate of parasitism is higher at intermediate disturbance levels. A. formosa cells are not randomly parasitized. Whatever the disturbance levels, fungi were found to mostly parasitize cell clusters forming non-stellate colonies.
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Responses of the planktonic diatom Asterionella formosa Hassall to abiotic environmental factors in a reservoir complex (south-eastern France)
Hydrobiologia, 2003Co-Authors: C Bertrand, Stéphanie Fayolle, Evelyne Franquet, Arlette CazaubonAbstract:The River Durance and its main tributary, the Verdon, are both highly regulated rivers flowing in south-eastern France. The course of both rivers is interrupted by a series of reservoirs with quite different geographical, morphometric, climatic, hydrodynamic and chemical characteristics. The planktonic diatom Asterionella formosa Hassall, which has undesirable cyclic effects from the water management point of view, was studied in this complex of reservoirs located in the Mediterranean region. The results indicate that only the monomictic calcareous reservoirs show a bimodal pattern of Asterionella formosa abundance. The population dynamics of this algal species was found to depend on both the morphometric features and the hydraulic mode of management (retention time) used at each reservoir, as well as on the physical (temperature, suspended matter) and chemical (nitrogen, silica, calcium) characteristics of the water.
G.h.m. Jaworski - One of the best experts on this subject based on the ideXlab platform.
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potassium dependence and phytoplankton ecology an experimental study
Freshwater Biology, 2003Co-Authors: G.h.m. Jaworski, J. F. Talling, S. I. HeaneyAbstract:1. Unialgal cultures of three species common in the freshwater phytoplankton were used to test limitation of specific growth rate and final yield in defined media of low K + concentration (range <0.3-6 μmol L -1 or mmol m -3 ). 2. Growth rate of the diatom Asterionella formosa was independent of K + concentration above 0.7 μmol L -1 . Final yield was dependent on initial concentration when accompanied by K + depletion below this concentration, but not by lesser depletion with more residual K + . Analyses of particulate K in the biomass indicated a mean final cell content of 2.8 μmol K 10 -8 cells, approximately 1.0% of the organic dry weight. 3. Less detailed work with the diatom Diatoma elongatum showed no dependence of growth rate or final yield upon the initial K + concentration in the range 0.8-3.2 m mol L -1 . The phytoflagellate Plagioselmis nannoplanctica suffered net mortality in the lowest concentration tested, 0.8 μmol L -1 . 4. Comparison with the range of K + concentration in natural fresh waters, including a depletion induced by an aquatic macrophyte, suggests that K + is unlikely to limit growth of phytoplankton. Nevertheless, there can be correlation of K + with lake trophy.
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sporangium differentiation and zoospore fine structure of the chytrid rhizophydium planktonicum a fungal parasite of Asterionella formosa
Fungal Biology, 1993Co-Authors: Gordon W Beakes, Hilda M Canter, G.h.m. JaworskiAbstract:Sporangium development in the fungal parasite Rhizophydium planktonicum has been followed by electron microscopy using dual clonal cultures. Following zoospore encystment on Asterionella , a fine germ-hypha is produced which penetrates the host via the girdle lamella. The sporangium develops directly from the cyst and becomes delimited from the germ-hypha by the formation of a septum. The pre-cleavage sporangium develops a thickened apical wall (a papilla) which ultimately gives rise to a vesicle which surrounds the emerging zoospores. This pattern of vesicle formation differs significantly from that so far described in other chytrid species. The nucleus undergoes mitosis before the sporangium cytoplasm becomes cleaved into uninucleate zoospore initials by the formation of an internal furrow system. Specialized zoospore organelles such as the lipid-associated rumposome and paracrystalline bodies are not formed until zoospore initial delimitation is almost completed. The fine-structure of the mature zoospore was used to evaluate the current taxonomic status of this species, particularly in relation to two other chytrid parasites of this host ( Zygorhizidium affluens and Z. planktonicum ). In zoospores of R. planktonicum , the ribosome aggregates typical of this genus are not delimited by endoplasmic reticulum. Zoospores of this species also contain paracrystalline bodies and dense occlusions in the region where the flagellum enters the spore body. These features have previously only been noted in other genera and therefore it is concluded that this species is probably not closely related to other Rhizophydium spp.
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comparative ultrastructural ontogeny of zoosporangia of zygorhizidium affluens and z planktonicum chytrid parasites of the diatom Asterionella formosa
Fungal Biology, 1992Co-Authors: Gordon W Beakes, Hilda M Canter, G.h.m. JaworskiAbstract:The fine-structural development of the small, 5–10 m, operculate zoosporangia of the monocentric chytrids Zygorhizidium affluens and Z. planktonicum , growing as epibionts on the planktonic diatom Asterionella formosa , is compared. In both species, following encystment and germination, the germ tube grows over the surface of the diatom frutule and penetrates the host cells by squeezing between the upper and lower girdle lamellae. As the cyst enlarges to form a sporangium, the single lipid globule breaks up and disperses, an operculum differentiates and the nucleus divides. In both species, cleavage of the cytoplasm into zoospore initials is mainly achieved by the infurrowing of the plasmamembrane, although there may be some contribution from internal cleavage vesicles. Flagellar axoneme profiles are not observed in the sporangia until cytoplasmic cleavage is well advanced. Specialized zoospore organelles, such as the rumposome fibrillar vesicles and endoplasmic reticulum-delimited ‘ribosome core’, do not form until the later stages of zoospore differentiation. The taxonomic and functional implications of these observations are discussed.
Piet Spaak - One of the best experts on this subject based on the ideXlab platform.
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Microsatellite sequences Asterionella formosa
2016Co-Authors: Silke Van Den Wyngaert, Markus Möst, Remo Freimann, Bastiaan W. Ibelings, Piet SpaakAbstract:Microsatellite sequences of Asterionella formosa, containing the repeat units and forward and reverse primer sites
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Hidden diversity in the freshwater planktonic diatom Asterionella formosa.
Molecular ecology, 2015Co-Authors: Silke Van Den Wyngaert, Bastiaan Willem Ibelings, Markus Möst, Remo Freimann, Piet SpaakAbstract:Many freshwater and marine algal species are described as having cosmopolitan distributions. Whether these widely distributed morphologically similar algae also share a similar gene pool remains often unclear. In the context of island biogeography theory, stronger spatial isolation deemed typical of freshwater lakes should restrict gene flow and lead to higher genetic differentiation among lakes. Using nine microsatellite loci, we investigate the genetic diversity of a widely distributed freshwater planktonic diatom, Asterionella formosa, across different lakes in Switzerland and the Netherlands. We applied a hierarchical spatial sampling design to determine the geographical scale at which populations are structured. A subset of the isolates was additionally analysed using amplified fragment length polymorphism (AFLP) markers. Our results revealed complex and unexpected population structure in A. formosa with evidence for both restricted and moderate to high gene flow at the same time. Different genetic markers (microsatellites and AFLPs) analysed with a variety of multivariate methods consistently revealed that genetic differentiation within lakes was much stronger than among lakes, indicating the presence of cryptic species within A. formosa. We conclude that the hidden diversity found in this study is expected to have implications for the further use of A. formosa in biogeographical, conservation and ecological studies. Further research using species-level phylogenetic markers is necessary to place the observed differentiation in an evolutionary context of speciation.
