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Michael Schagerl - One of the best experts on this subject based on the ideXlab platform.
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induction of sexual reproduction and zygospore patterns in the filamentous green alga Spirogyra conjugatophyceae zygnematales
Journal of BioScience and Biotechnology, 2017Co-Authors: Mostafa M Elsheekh, Michael Schagerl, M M Gharieb, Ghada Abou ElsoudAbstract:Morphotaxonomy, ecological preferences and biological characterization of algal taxa of order Zygnematales (Conjugatophyceae, Chlorophyta), mainly the freshwater species Spirogyra, Zygnema, and Mougeotia are still poorly understood and need further in-depth investigations. In this study, different Spirogyra strains were examined to characterize their abilities in conjugation and formation of zygospores under different environmental conditions. It was found that 16:8-h light:dark photoperiod is the best condition to induce the conjugation and zygospore formation. Moreover, the sexual reproduction was noticed to be motivated with increasing the light intensity up to 85 µmol photons m-2s-1 and no conjugation was observed at 35 µmol photons m-2s-1. The attribute of conjugation in red and blue lights, respectively, never equalized that in the white light even with a high intensity. pH value (7.5) was the most suitable niche for induction of sexual reproduction in the studied Spirogyra strains. An increase of CO2 in the atmosphere, provided by NaHCO3 solution, did not enhance the sexual reproduction. Cultivation of the investigated Spirogyra strains on 0.003% CaCl2-containing agarized Pringhsheim´s medium (1/2 conc. and without nitrogen) induced the conjugation process as in case of CaCl2 omitted. UV radiation completely inhibited the conjugation at all growth conditions.
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A brief introduction to the morphological species concept of Spirogyra and emanating problems
Algological Studies, 2015Co-Authors: Michael Schagerl, Melanie ZwirnAbstract:The zygnematalean genus Spirogyra is a common freshwater alga and easily recognized by its spirally coiled chloroplasts. The traditional species delimitation within Spirogyra is based upon morphology, considering both asexual and sexual stages of its life cycle. In this study, we identified 16 Spirogyra strains originating from 14 sampling sites of Central Europe down to the species level and compared our observations to species descriptions provided in monographs. This case study demonstrates the uncertainties underlying the exclusive application of the morphological species concept, which indicates that many Spirogyra species might have been described too narrowly. We therefore suggest a polyphasic approach including molecular, morphological and ecophysiological traits. We discuss recent findings on Spirogyra phylogeny based on molecular tools and provide a possible solution to handle the current problems of Spirogyra taxonomy.
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Hidden genetic diversity in the green alga Spirogyra (Zygnematophyceae, Streptophyta)
BMC Evolutionary Biology, 2012Co-Authors: Charlotte Chen, Thomas Proschold, Michael H J Barfuss, Michael SchagerlAbstract:Background The unbranched filamentous green alga Spirogyra (Streptophyta, Zygnemataceae) is easily recognizable based on its vegetative morphology, which shows one to several spiral chloroplasts. This simple structure falsely points to a low genetic diversity: Spirogyra is commonly excluded from phylogenetic analyses because the genus is known as a long-branch taxon caused by a high evolutionary rate. Results We focused on this genetic diversity and sequenced 130 Spirogyra small subunit nuclear ribosomal DNA (SSU rDNA) strands of different origin. The resulting SSU rDNA sequences were used for phylogenetic analyses using complex evolutionary models (posterior probability, maximum likelihood, neighbor joining, and maximum parsimony methods). The sequences were between 1672 and 1779 nucleotides long. Sequence comparisons revealed 53 individual clones, but our results still support monophyly of the genus. Our data set did not contain a single slow-evolving taxon that would have been placed on a shorter branch compared to the remaining sequences. Out of 130 accessions analyzed, 72 showed a secondary loss of the 1506 group I intron, which formed a long-branched group within the genus. The phylogenetic relationship to the genus Spirotaenia was not resolved satisfactorily. The genetic distance within the genus Spirogyra exceeded the distances measured within any other genus of the remaining Zygnemataceae included in this study. Conclusion Overall, we define eight distinct clades of Spirogyra , one of them including the genus Sirogonium . A large number of non-homoplasious synapomorphies (NHS; 114 NHS in total) was found for Spirogyra (41 NHS) and for each clade (totaling 73 NHS). This emphasizes the high genetic diversity of this genus and the distance to the remaining Zygnematophyceae.
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Hidden genetic diversity in the green alga Spirogyra (Zygnematophyceae, Streptophyta)
BMC evolutionary biology, 2012Co-Authors: Charlotte Chen, Thomas Proschold, Michael H J Barfuss, Michael SchagerlAbstract:The unbranched filamentous green alga Spirogyra (Streptophyta, Zygnemataceae) is easily recognizable based on its vegetative morphology, which shows one to several spiral chloroplasts. This simple structure falsely points to a low genetic diversity: Spirogyra is commonly excluded from phylogenetic analyses because the genus is known as a long-branch taxon caused by a high evolutionary rate. We focused on this genetic diversity and sequenced 130 Spirogyra small subunit nuclear ribosomal DNA (SSU rDNA) strands of different origin. The resulting SSU rDNA sequences were used for phylogenetic analyses using complex evolutionary models (posterior probability, maximum likelihood, neighbor joining, and maximum parsimony methods). The sequences were between 1672 and 1779 nucleotides long. Sequence comparisons revealed 53 individual clones, but our results still support monophyly of the genus. Our data set did not contain a single slow-evolving taxon that would have been placed on a shorter branch compared to the remaining sequences. Out of 130 accessions analyzed, 72 showed a secondary loss of the 1506 group I intron, which formed a long-branched group within the genus. The phylogenetic relationship to the genus Spirotaenia was not resolved satisfactorily. The genetic distance within the genus Spirogyra exceeded the distances measured within any other genus of the remaining Zygnemataceae included in this study. Overall, we define eight distinct clades of Spirogyra, one of them including the genus Sirogonium. A large number of non-homoplasious synapomorphies (NHS; 114 NHS in total) was found for Spirogyra (41 NHS) and for each clade (totaling 73 NHS). This emphasizes the high genetic diversity of this genus and the distance to the remaining Zygnematophyceae.
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slow evolution of 1506 group i intron in Spirogyra link 1820 zygnematophyceae streptophyta a fast evolving lineage in the zygnemataceae
Fottea, 2012Co-Authors: Charlotte Chen, Michael SchagerlAbstract:Phylogenetic analyses of SSU rDNA sequences of 130 Spirogyra strains have revealed that these strains were subdivided into eight clades. Approximately 60% of the assessed strains (clades A-D) contain a 1506 group I intron, whereas strains without introns form individual clades (E-H). The Spirogyra intron shared the common insertion site of the Zygnematalean intron (position 1506 relative to the Escherichia coli small-subunit rRNA). Phylogenetic analyses of the Spirogyra group I intron showed the monophyletic origin within the Zygnematophyceae. Therefore, we assume the secondary loss of the intron in clades E-H is caused by the high evolutionary rate of Spirogyra and its long evolutionary history. The Spirogyra intron belongs to the IC group I introns and shares many common features with the intron of other Zygnematophyceae (the typical domain structure (P1-P9), the base composition, the highly conserved regions the U preceding the 5' splice site and the G to which it pairs, and the G preceding the 3' splice site are typical for IC group I intron). Spirogyra group I introns exhibit features of early desmids (optional P2 domain) as well as of later diverging desmids (variation from the typical L5b-GAAA tetraloop). The P2 domain shows an additional optional P2 sub-domain in clade B. Surprisingly, the mutation rate of the Spirogyra SSU rRNA exceeds the rate of the intron by far. Evolutionary rates differ significantly within the Spirogyra SSU rRNA accessions, but not within the respective group I intron sequences.
Charlotte Chen - One of the best experts on this subject based on the ideXlab platform.
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hidden genetic diversity in the green alga Spirogyra zygnematophyceae streptophyta
BMC Evolutionary Biology, 2012Co-Authors: Charlotte Chen, Thomas Proschold, Michael H J Barfuss, Michael SchagerlAbstract:Background The unbranched filamentous green alga Spirogyra (Streptophyta, Zygnemataceae) is easily recognizable based on its vegetative morphology, which shows one to several spiral chloroplasts. This simple structure falsely points to a low genetic diversity: Spirogyra is commonly excluded from phylogenetic analyses because the genus is known as a long-branch taxon caused by a high evolutionary rate.
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Hidden genetic diversity in the green alga Spirogyra (Zygnematophyceae, Streptophyta)
BMC Evolutionary Biology, 2012Co-Authors: Charlotte Chen, Thomas Proschold, Michael H J Barfuss, Michael SchagerlAbstract:Background The unbranched filamentous green alga Spirogyra (Streptophyta, Zygnemataceae) is easily recognizable based on its vegetative morphology, which shows one to several spiral chloroplasts. This simple structure falsely points to a low genetic diversity: Spirogyra is commonly excluded from phylogenetic analyses because the genus is known as a long-branch taxon caused by a high evolutionary rate. Results We focused on this genetic diversity and sequenced 130 Spirogyra small subunit nuclear ribosomal DNA (SSU rDNA) strands of different origin. The resulting SSU rDNA sequences were used for phylogenetic analyses using complex evolutionary models (posterior probability, maximum likelihood, neighbor joining, and maximum parsimony methods). The sequences were between 1672 and 1779 nucleotides long. Sequence comparisons revealed 53 individual clones, but our results still support monophyly of the genus. Our data set did not contain a single slow-evolving taxon that would have been placed on a shorter branch compared to the remaining sequences. Out of 130 accessions analyzed, 72 showed a secondary loss of the 1506 group I intron, which formed a long-branched group within the genus. The phylogenetic relationship to the genus Spirotaenia was not resolved satisfactorily. The genetic distance within the genus Spirogyra exceeded the distances measured within any other genus of the remaining Zygnemataceae included in this study. Conclusion Overall, we define eight distinct clades of Spirogyra , one of them including the genus Sirogonium . A large number of non-homoplasious synapomorphies (NHS; 114 NHS in total) was found for Spirogyra (41 NHS) and for each clade (totaling 73 NHS). This emphasizes the high genetic diversity of this genus and the distance to the remaining Zygnematophyceae.
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Hidden genetic diversity in the green alga Spirogyra (Zygnematophyceae, Streptophyta)
BMC evolutionary biology, 2012Co-Authors: Charlotte Chen, Thomas Proschold, Michael H J Barfuss, Michael SchagerlAbstract:The unbranched filamentous green alga Spirogyra (Streptophyta, Zygnemataceae) is easily recognizable based on its vegetative morphology, which shows one to several spiral chloroplasts. This simple structure falsely points to a low genetic diversity: Spirogyra is commonly excluded from phylogenetic analyses because the genus is known as a long-branch taxon caused by a high evolutionary rate. We focused on this genetic diversity and sequenced 130 Spirogyra small subunit nuclear ribosomal DNA (SSU rDNA) strands of different origin. The resulting SSU rDNA sequences were used for phylogenetic analyses using complex evolutionary models (posterior probability, maximum likelihood, neighbor joining, and maximum parsimony methods). The sequences were between 1672 and 1779 nucleotides long. Sequence comparisons revealed 53 individual clones, but our results still support monophyly of the genus. Our data set did not contain a single slow-evolving taxon that would have been placed on a shorter branch compared to the remaining sequences. Out of 130 accessions analyzed, 72 showed a secondary loss of the 1506 group I intron, which formed a long-branched group within the genus. The phylogenetic relationship to the genus Spirotaenia was not resolved satisfactorily. The genetic distance within the genus Spirogyra exceeded the distances measured within any other genus of the remaining Zygnemataceae included in this study. Overall, we define eight distinct clades of Spirogyra, one of them including the genus Sirogonium. A large number of non-homoplasious synapomorphies (NHS; 114 NHS in total) was found for Spirogyra (41 NHS) and for each clade (totaling 73 NHS). This emphasizes the high genetic diversity of this genus and the distance to the remaining Zygnematophyceae.
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slow evolution of 1506 group i intron in Spirogyra link 1820 zygnematophyceae streptophyta a fast evolving lineage in the zygnemataceae
Fottea, 2012Co-Authors: Charlotte Chen, Michael SchagerlAbstract:Phylogenetic analyses of SSU rDNA sequences of 130 Spirogyra strains have revealed that these strains were subdivided into eight clades. Approximately 60% of the assessed strains (clades A-D) contain a 1506 group I intron, whereas strains without introns form individual clades (E-H). The Spirogyra intron shared the common insertion site of the Zygnematalean intron (position 1506 relative to the Escherichia coli small-subunit rRNA). Phylogenetic analyses of the Spirogyra group I intron showed the monophyletic origin within the Zygnematophyceae. Therefore, we assume the secondary loss of the intron in clades E-H is caused by the high evolutionary rate of Spirogyra and its long evolutionary history. The Spirogyra intron belongs to the IC group I introns and shares many common features with the intron of other Zygnematophyceae (the typical domain structure (P1-P9), the base composition, the highly conserved regions the U preceding the 5' splice site and the G to which it pairs, and the G preceding the 3' splice site are typical for IC group I intron). Spirogyra group I introns exhibit features of early desmids (optional P2 domain) as well as of later diverging desmids (variation from the typical L5b-GAAA tetraloop). The P2 domain shows an additional optional P2 sub-domain in clade B. Surprisingly, the mutation rate of the Spirogyra SSU rRNA exceeds the rate of the intron by far. Evolutionary rates differ significantly within the Spirogyra SSU rRNA accessions, but not within the respective group I intron sequences.
Hisayoshi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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Identification of 13 Spirogyra species (Zygnemataceae) by traits of sexual reproduction induced under laboratory culture conditions
Scientific Reports, 2019Co-Authors: Tomoyuki Takano, Hisato Ikegaya, Sumio Higuchi, Ryo Matsuzaki, Masanobu Kawachi, Fumio Takahashi, Hisayoshi NozakiAbstract:The genus Spirogyra is abundant in freshwater habitats worldwide, and comprises approximately 380 species. Species assignment is often difficult because identification is based on the characteristics of sexual reproduction in wild-collected samples and spores produced in the field or laboratory culture. We developed an identification procedure based on an improved methodology for inducing sexual conjugation in laboratory-cultivated filaments. We tested the modified procedure on 52 newly established and genetically different strains collected from diverse localities in Japan. We induced conjugation or aplanospore formation under controlled laboratory conditions in 15 of the 52 strains, which allowed us to identify 13 species. Two of the thirteen species were assignable to a related but taxonomically uncertain genus, Temnogyra , based on the unique characteristics of sexual reproduction. Our phylogenetic analysis demonstrated that the two Temnogyra species are included in a large clade comprising many species of Spirogyra . Thus, separation of Temnogyra from Spirogyra may be untenable, much as the separation of Sirogonium from Spirogyra is not supported by molecular analyses.
Richard M. Mccourt - One of the best experts on this subject based on the ideXlab platform.
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Identity and phylogenetic placement of Spirogyra species (Zygnematophyceae, Charophyta) from California streams and elsewhere1
Journal of phycology, 2013Co-Authors: Rosalina Stancheva, Richard M. Mccourt, John D. Hall, Robert G. SheathAbstract:Diversity of the filamentous green algae in the genus Spirogyra (Zygnematophyceae) was investigated from more than 1,200 stream samples from California. We identified 12 species of Spirogyra not previously known for California (CA), including two species new to science, Spirogyra californica sp. nov. and Spirogyra juliana sp. nov. Environmental preferences of the Californian species are discussed in the light of their restricted distribution to stream habitats with contrasting nutrient levels. We also investigated the systematic relationships of Spirogyra species from several continents using the chloroplast-encoded genes ribulose-1,5-bisphosphate carboxylase/hydrogenase large subunit (rbcL) and the beta subunit of the ATP synthase (atpB). Californian species were positioned in most major clades of Spirogyra. The phylogeny of Spirogyra and its taxonomic implications are discussed, such as the benefits of combining structural and molecular data for more accurate and consistent species identification. Considerable infraspecific genetic variation of globally distributed Spirogyra species was observed across continental scales. This finding suggests that structurally similar species from distant regions may be genetically dissimilar and that Spirogyra may contain a large number of cryptic species. Correlating the morphological and genetic variation within the genus will be a major challenge for future researchers.
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PHYLOGENY OF Spirogyra AND SIROGONIUM (ZYGNEMATOPHYCEAE) BASED ON RBCL SEQUENCE DATA1
Journal of Phycology, 2005Co-Authors: Christopher S. Drummond, Kenneth G. Karol, Charles F. Delwiche, John D. Hall, Richard M. MccourtAbstract:DNA sequence data were obtained for the gene encoding the large subunit of RUBISCO (rbcL) from 26 strains of Spirogyra and seven of Sirogonium, using as outgroups 10 genera in the Zygnematales and Desmidiales (Closterium, Cosmarium, Cylindrocystis, Gonatozygon, Mesotaenium, Netrium, Penium, Zygnema, Zygnemopsis, Zygogonium). Sequence data were analyzed using maximum parsimony (MP), maximum likelihood (ML), and Bayesian inference (BI), with bootstrap replication (MP, ML) and posterior probabilities (BI) as measures of support. MP, ML, and BI analyses of the rbcL data strongly support a single clade containing Spirogyra and Sirogonium. The Spirogyra taxa are monophyletic, with the exception of Spirogyra maxima (Hassall) Wittrock, which is nested within a clade with Sirogonium and shares with them the characters of loosely spiraled chloroplasts (< 1 complete turn per cell) and anisogamy of gametangial cells; S. maxima differs from Sirogonium in displaying well-defined conjugation tubes rather than a tubeless connection involving bending (genuflection) of filaments. The ML and BI analyses place this Sirogonium/Spirogyra maxima clade sister to the remaining Spirogyra. Morphological differences among strains of Spirogyra grouped together on the basis of rbcL data, including laboratory strains derived from clonal cultures (Spirogyra communis, S. pratensis), indicate that some characters (filament width, chloroplast number) used in the traditional taxonomy of this group are poor measures of species identity. However, some characters such as replicate end walls and loose spiraling of chloroplasts may be synapomorphies for Spirogyra clades.
Simon A. Townsend - One of the best experts on this subject based on the ideXlab platform.
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A model to predict the response of the benthic macroalga Spirogyra to reduced base flow in the tropical Australia
River Research and Applications, 2009Co-Authors: Simon A. Townsend, Anna PadovanAbstract:A model was developed to predict the impact of reduced dry season base flow, due to groundwater and river extraction, on the standing crop of Spirogyra along an 18 km reach of the Daly River, located in the Australian wet/dry tropics. The alga can constitute up to 40% of the primary producer standing crop and is a food source for turtles. Outputs from a two-dimensional hydrodynamic model and the observed maximum biomass of Spirogyra for a range of shear velocities were used to predict the maximum potential standing crop (MPSC) of Spirogyra. With reduced flow, hydraulic conditions became less favourable for the growth of Spirogyra, whilst the area of suitable substrata was not as responsive. The MPSC of Spirogyra was predicted for the minimum dry season flow for a 47 year period of hydrographic record using two hypothetical extraction scenarios. Both scenarios produced MPSCs that were frequently less than the minimum crop under natural flows and underscored the need for a minimum flow to maintain a MPSC that exceeded the historic minimum. The MPSC, however, is unlikely to be attained due to autogenic sloughing, nutrient supply and other factors, thus the model is best considered an index of the impact of reduced river flows. The model communicates a reduction in the standing crop of Spirogyra due to reduced dry season base flows and an inferred impact on its dependent fauna and the river's nutrient dynamics. The model demonstrates the utility of applying a benthic algal model to evaluate the ecological impact of modified flow regimes and contribute to environmental flow recommendations.
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The seasonal accrual and loss of benthic algae (Spirogyra) in the Daly River, an oligotrophic river in tropical Australia
Marine and Freshwater Research, 2005Co-Authors: Simon A. Townsend, Armando PadovanAbstract:The hierarchy of factors that control the growth and biomass of Spirogyra sp. was examined for an 18-km reach of the Daly River in the wet/dry tropics of northern Australia. On an annual temporal scale, hydrological disturbances control Spirogyra. Over the wet season (typically December-April), frequent runoff events prevent the colonisation and growth of Spirogyra in the Daly River. This is followed, however, by a lengthy period (typically May-November) without hydrological disturbances and river velocities that favour benthic algal growth. In 2001, Spirogyra became visible in mid-May, then grew to reach a maximum biomass in early August of 28 mg m -2 of chlorophyll a. The standing crop of Spirogyra was primarily determined by the availability of gravel substrate and the velocity and shear stress at the river-bed. Photosynthetically available radiation (200-800 μEm -2 s -1 ) reaching the river-bed should not have limited algal growth, though self shading within the Spirogyra mats may have been important. Although the growth rate of Spirogyra was probably limited by nutrients, the maximum biomass was constrained by autogenic sloughing. The biomass of Spirogyra steadily declined to half its maximum in early October despite favourable river velocities, most likely a result of nutrient limitation. Spirogyra was then removed from the river by the first major runoff event of the wet season in late October. The hierarchy of factors that control benthic algal biomass in the Daly River are the same as in lower latitudes, though the long period of favourable river velocities when smaller scale, proximate factors (e.g. nutrients, shear stress) control biomass should be noted.
