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Patrick J. Keeling - One of the best experts on this subject based on the ideXlab platform.
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Splicing and Transcription Differ between Spore and Intracellular Life Stages in the Parasitic Microsporidia
2020Co-Authors: Erin E Gill, Patrick J. Keeling, Nicolas Corradi, Renny C H Lee, Cameron J Grisdale, Valerie O Limpright, Naomi M FastAbstract:Abstract Microsporidia are a diverse group of highly derived fungal relatives that are intracellular parasites of many animals. Both transcription and introns have been shown to be unusual in Microsporidia: The complete genome of the human parasite Encephalitozoon cuniculi has only a few very short introns, and two distantly related Microsporidian spores have been shown to harbor transcripts encoding several genes that overlap on different strands. However, Microsporidia alternate between two life stages: the intracellular proliferative stage and the extracellular and largely metabolically dormant infectious spore. To date, most studies have focused on the spore. Here, we have compared transcription profiles for a number of genes from both life stages of Microsporidia and found major differences in both the prevalence of overlapping transcription and splicing. Specifically, spore transcripts in E. cuniculi have longer 5# untranslated regions, overlap more frequently with upstream genes, and have a significantly higher number of transcription initiation sites compared with intracellular transcripts from the same species. In addition, we demonstrate that splicing occurs exclusively in the intracellular stage and not in spore messenger RNAs (mRNAs) in both E. cuniculi and the distantly related Antonospora locustae. These differences between the Microsporidian life stages raise questions about the functional importance of transcripts in the spore. We hypothesize that at least some transcripts in spores are a product of the cell's transition into a dormant state and that these unusual mRNAs could play a structural role rather than an informational one
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A Broad Distribution of the Alternative Oxidase in Microsporidian Parasites
2013Co-Authors: Bryony A. P. Williams, Lena Burri, Catherine Elliot, Yasutoshi Kido, Kiyoshi Kita, Anthony L, Patrick J. KeelingAbstract:Microsporidia are a group of obligate intracellular parasitic eukaryotes that were considered to be amitochondriate until the recent discovery of highly reduced mitochondrial organelles called mitosomes. Analysis of the complete genome of Encephalitozoon cuniculi revealed a highly reduced set of proteins in the organelle, mostly related to the assembly of ironsulphur clusters. Oxidative phosphorylation and the Krebs cycle proteins were absent, in keeping with the notion that the Microsporidia and their mitosomes are anaerobic, as is the case for other mitosome bearing eukaryotes, such as Giardia. Here we provide evidence opening the possibility that mitosomes in a number of Microsporidian lineages are not completely anaerobic. Specifically, we have identified and characterized a gene encoding the alternative oxidase (AOX), a typically mitochondrial terminal oxidase in eukaryotes, in the genomes of several distantly related Microsporidian species, even though this gene is absent from the complete genome of E. cuniculi. In order to confirm that these genes encode functional proteins, AOX genes from both A. locustae and T. hominis were over-expressed in E. coli and AOX activity measured spectrophotometrically using ubiquinol-1 (UQ-1) as substrate. Both A. locustae and T. hominis AOX proteins reduced UQ-1 in a cyanide and antimycin-resistant manner that was sensitive to ascofuranone, a potent inhibitor of the trypanosomal AOX. The physiological role of AOX Microsporidia may be to reoxidise reducing equivalents produced b
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Evolution of the sex-Related Locus and Genomic Features Shared in Microsporidia and Fungi
2013Co-Authors: Soo Chan Lee, Patrick J. Keeling, Nicolas Corradi, Fred S Dietrich, Sylvia Doan, Joseph HeitmanAbstract:Background: Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the Microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that Microsporidia share a particularly close evolutionary relationship with the zygomycetes. Methodology/Principal Findings: Here we expanded this analysis and also examined a putative sex-locus for variability between Microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the Microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and Microsporidians. One locus previously found to be conserved in many Microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sexrelated locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According t
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evolution of the sex related locus and genomic features shared in Microsporidia and fungi
PLOS ONE, 2010Co-Authors: Soo Chan Lee, Patrick J. Keeling, Nicolas Corradi, Fred S Dietrich, Sylvia Doan, Joseph HeitmanAbstract:Background: Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the Microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that Microsporidia share a particularly close evolutionary relationship with the zygomycetes. Methodology/Principal Findings: Here we expanded this analysis and also examined a putative sex-locus for variability between Microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the Microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and Microsporidians. One locus previously found to be conserved in many Microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sexrelated locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According to sequence-based phylogenetic analyses, the TPT and RNA helicase genes flanking the HMG genes are paralogous rather than orthologous between zygomycetes and Microsporidians. Conclusion/Significance: The unique genomic hallmarks between Microsporidia and fungi are independent of sequence based phylogenetic comparisons and further contribute to define the borders of the fungal kingdom and support the classification of Microsporidia as unusual derived fungi. And the sex/sex-related loci appear to have been subject to frequent gene conversion and translocations in Microsporidia and zygomycetes.
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A broad distribution of the alternative oxidase in Microsporidian parasites.
PLOS Pathogens, 2010Co-Authors: Bryony A. P. Williams, Lena Burri, Catherine Elliot, Yasutoshi Kido, Kiyoshi Kita, Anthony L. Moore, Patrick J. KeelingAbstract:Microsporidia are a group of obligate intracellular parasitic eukaryotes that were considered to be amitochondriate until the recent discovery of highly reduced mitochondrial organelles called mitosomes. Analysis of the complete genome of Encephalitozoon cuniculi revealed a highly reduced set of proteins in the organelle, mostly related to the assembly of iron-sulphur clusters. Oxidative phosphorylation and the Krebs cycle proteins were absent, in keeping with the notion that the Microsporidia and their mitosomes are anaerobic, as is the case for other mitosome bearing eukaryotes, such as Giardia. Here we provide evidence opening the possibility that mitosomes in a number of Microsporidian lineages are not completely anaerobic. Specifically, we have identified and characterized a gene encoding the alternative oxidase (AOX), a typically mitochondrial terminal oxidase in eukaryotes, in the genomes of several distantly related Microsporidian species, even though this gene is absent from the complete genome of E. cuniculi. In order to confirm that these genes encode functional proteins, AOX genes from both A. locustae and T. hominis were over-expressed in E. coli and AOX activity measured spectrophotometrically using ubiquinol-1 (UQ-1) as substrate. Both A. locustae and T. hominis AOX proteins reduced UQ-1 in a cyanide and antimycin-resistant manner that was sensitive to ascofuranone, a potent inhibitor of the trypanosomal AOX. The physiological role of AOX Microsporidia may be to reoxidise reducing equivalents produced by glycolysis, in a manner comparable to that observed in trypanosomes.
S. Bjørnson - One of the best experts on this subject based on the ideXlab platform.
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The convergent lady beetle, Hippodamia convergens Guérin-Méneville and its endoparasitoid Dinocampus coccinellae (Schrank): the effect of a microsporidium on parasitoid development and host preference.
Journal of invertebrate pathology, 2013Co-Authors: T. Saito, S. BjørnsonAbstract:Convergent lady beetles, Hippodamia convergens Guerin-Meneville are host to the braconid endoparasitoid, Dinocampus coccinellae (Schrank) and the Microsporidian pathogen, Tubulinosema hippodamiae. The interrelationship between the endoparasitoid and the pathogen in H. convergens adults under laboratory conditions was examined by quantifying the effect of microsporidiosis on D. coccinellae development and host preference. Uninfected wasps were provided either uninfected or T. hippodamiae-infected beetles as hosts and the development of their progeny was observed over 30 days. The duration of endoparasitoid development from egg deposition in the host until adult eclosion for D. coccinellae did not differ significantly, regardless of the infection status of the host beetle. All wasp progeny that developed within, and emerged from, T. hippodamiae-infected beetles were infected with the Microsporidian pathogen (n = 48; 100% transmission). Infected D. coccinellae adults were also provided either uninfected or T. hippodamiae infected host beetles so that the development of their progeny could be assessed over 30 days. Endoparasitoid development did not differ significantly; however, a significantly greater proportion of beetles stung by Microsporidia-infected wasps did not contain an endoparasitoid larva when dissected at the end of the 30-day trial when compared to those stung by uninfected wasps. This suggests that the pathogen may reduce wasp fecundity or egg viability. Examination of paraffin-embedded D. coccinellae adult tissues revealed an extensive Microsporidian infection throughout all major organs and tissues with exception of the ovary. During host choice trials, uninfected and Microsporidia-infected D. coccinellae adults pursued, took an ovipositional stance, and attacked uninfected beetles more often than Microsporidia-infected hosts but these observations did not differ significantly (P > 0.05).
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Effects of an unidentified microsporidium on the convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), used for biological control
Journal of Invertebrate Pathology, 2006Co-Authors: P. Joudrey, S. BjørnsonAbstract:Convergent lady beetles, Hippodamia convergens Guerin-Meneville, are collected from overwintering sites in California and redistributed for aphid control in home gardens and agroecosystems. The effects of an unidentified microsporidium on the life history characteristics of commercially available H. convergens were examined. Mean development for Microsporidia-infected and uninfected H. convergens was 15.40+/-0.14 and 14.76+/-0.16 days, respectively (P=0.01). Larval mortality did not differ significantly. Cumulative mean egg production for Microsporidia-infected and uninfected females was 545.8+/-92.6 and 928.3+/-86.4 eggs, respectively (P=0.004) and mean survival was 64.5+/-5.6 and 77.1+/-4.5 days, respectively (P=0.04). Microsporidian spores (3.6x2.4 microm) are similar in size to those of Nosema hippodamiae.
Louis M Weiss - One of the best experts on this subject based on the ideXlab platform.
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human Microsporidian pathogen encephalitozoon intestinalis impinges on enterocyte membrane trafficking and signaling
Journal of Cell Science, 2021Co-Authors: Juan Flores, Louis M Weiss, Peter M Takvorian, Ann Cali, Nan GaoAbstract:ABSTRACT Microsporidia are a large phylum of obligate intracellular parasites. Approximately a dozen species of Microsporidia infect humans, where they are responsible for a variety of diseases and occasionally death, especially in immunocompromised individuals. To better understand the impact of Microsporidia on human cells, we infected human colonic Caco2 cells with Encephalitozoon intestinalis, and showed that these enterocyte cultures can be used to recapitulate the life cycle of the parasite, including the spread of infection with infective spores. Using transmission electron microscopy, we describe this lifecycle and demonstrate nuclear, mitochondrial and microvillar alterations by this pathogen. We also analyzed the transcriptome of infected cells to reveal host cell signaling alterations upon infection. These high-resolution imaging and transcriptional profiling analysis shed light on the impact of the Microsporidial infection on its primary human target cell type. This article has an associated First Person interview with the first authors of the paper.
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genome sequence surveys of brachiola algerae and edhazardia aedis reveal Microsporidia with low gene densities
BMC Genomics, 2008Co-Authors: Bryony A. P. Williams, Naomi M Fast, Louis M Weiss, Renny C H Lee, James J Becnel, Patrick J. KeelingAbstract:Microsporidia are well known models of extreme nuclear genome reduction and compaction. The smallest Microsporidian genomes have received the most attention, but genomes of different species range in size from 2.3 Mb to 19.5 Mb and the nature of the larger genomes remains unknown. Here we have undertaken genome sequence surveys of two diverse Microsporidia, Brachiola algerae and Edhazardia aedis. In both species we find very large intergenic regions, many transposable elements, and a low gene-density, all in contrast to the small, model Microsporidian genomes. We also find no recognizable genes that are not also found in other surveyed or sequenced Microsporidian genomes. Our results demonstrate that Microsporidian genome architecture varies greatly between Microsporidia. Much of the genome size difference could be accounted for by non-coding material, such as intergenic spaces and retrotransposons, and this suggests that the forces dictating genome size may vary across the phylum.
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Microsporidia: emerging pathogenic protists.
Acta tropica, 2001Co-Authors: Louis M WeissAbstract:Microsporidia are eukaryotic spore forming obligate intracellular protozoan parasites first recognized over 100 years ago. These organisms infect all of the major animal groups and are now recognized as opportunistic pathogens of humans. Microsporidian spores are common in the environment and Microsporidia pathogenic to humans have been found in water supplies. The genera Nosema, Vittaforma, Brachiola, Pleistophora, Encephalitozoon, Enterocytozoon, Septata (reclassified to Encephalitozoon) and Trachipleistophora have been found in human infections. These organisms have the smallest known eukaryotic genomes. Microsporidian ribosomal RNA sequences have proven useful as diagnostic tools as well as for phylogenetic analysis. Recent phylogenetic analysis suggests that Microsporidia are related to the fungi. These organisms are defined by the presence of a unique invasion organelle consisting of a single polar tube that coils around the interior of the spore. All Microsporidia exhibit the same response to stimuli, that is, the polar tube discharges from the anterior pole of the spore in an explosive reaction. If the polar tube is discharged next to a cell, it can pierce the cell and transfer its sporoplasm into the cell. A technique was developed for the purification of polar tube proteins (PTPs) using differential extraction followed by reverse phase HPLC. This method was used to purify the PTPs from Glugea americanus, Encephalitozoon cuniculi, Enc. hellem and Enc. intestinalis. These PTPs demonstrate conserved characteristics such as solubility, hydrophobicity, mass, proline content and immunologic epitopes. The major PTP gene from Enc. cuniculi and Enc. hellem has been cloned and expressed in vitro. The gene sequences support the importance of ER and in the formation of the polar tube as suggested by morphologic studies. Analysis of the cloned proteins also indicates that secondary structural characteristics are conserved. These characteristics are probably important in the function of this protein during the eversion/assembly of the polar tube and in providing elasticity and resiliency for sporoplasm passage.
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Immune response to Encephalitozoon cuniculi infection
Microbes and infection, 2001Co-Authors: Imtiaz A. Khan, Magali Moretto, Louis M WeissAbstract:Microsporidia are obligate intracellular parasites, which can cause complications in immunocompromised individuals. Very little is known about the host immune response generated against these infectious agents. Encephalitozoon cuniculi is the best studied Microsporidian and the protective immune response against this parasite is mediated by cytotoxic CD8+ T cells.
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drug treatment of microsporidiosis
Drug Resistance Updates, 2000Co-Authors: Sylvia F Costa, Louis M WeissAbstract:Abstract Microsporidia are ubiquitous organisms that are emerging pathogens in humans. These are most likely zoonotic and/or waterborne infections. In the immunosuppressed host, such as those treated with immunosuppressive drugs or infected with human immunodeficiency virus particularly at advanced stages of the disease, Microsporidia can produce a wide range of clinical diseases. The most common manifestation is gastrointestinal tract infection; however, encephalitis, ocular infection, sinusitis, myositis and disseminated infection have also been described. In addition, these organisms have been reported in immune competent individuals. Multiple genera are involved in these infections and different organisms can result in distinct clinical pictures. Differences in clinical and parasitologic response to various therapeutic agents have emerged from clinical, as well as in vitro and in vivo studies. Currently there are no precisely defined guidelines for the optimal treatment of Microsporidial infections. This article reviews the available data on compounds with in vitro activity and/or in vivo efficacy for Microsporidial infections.
Joseph Heitman - One of the best experts on this subject based on the ideXlab platform.
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Evolution of the sex-Related Locus and Genomic Features Shared in Microsporidia and Fungi
2013Co-Authors: Soo Chan Lee, Patrick J. Keeling, Nicolas Corradi, Fred S Dietrich, Sylvia Doan, Joseph HeitmanAbstract:Background: Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the Microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that Microsporidia share a particularly close evolutionary relationship with the zygomycetes. Methodology/Principal Findings: Here we expanded this analysis and also examined a putative sex-locus for variability between Microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the Microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and Microsporidians. One locus previously found to be conserved in many Microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sexrelated locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According t
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evolution of the sex related locus and genomic features shared in Microsporidia and fungi
PLOS ONE, 2010Co-Authors: Soo Chan Lee, Patrick J. Keeling, Nicolas Corradi, Fred S Dietrich, Sylvia Doan, Joseph HeitmanAbstract:Background: Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the Microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that Microsporidia share a particularly close evolutionary relationship with the zygomycetes. Methodology/Principal Findings: Here we expanded this analysis and also examined a putative sex-locus for variability between Microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the Microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and Microsporidians. One locus previously found to be conserved in many Microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sexrelated locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According to sequence-based phylogenetic analyses, the TPT and RNA helicase genes flanking the HMG genes are paralogous rather than orthologous between zygomycetes and Microsporidians. Conclusion/Significance: The unique genomic hallmarks between Microsporidia and fungi are independent of sequence based phylogenetic comparisons and further contribute to define the borders of the fungal kingdom and support the classification of Microsporidia as unusual derived fungi. And the sex/sex-related loci appear to have been subject to frequent gene conversion and translocations in Microsporidia and zygomycetes.
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Evolution of the sex-related locus and genomic features shared in Microsporidia and fungi.
Public Library of Science (PLoS), 2010Co-Authors: Soo Chan Lee, Patrick J. Keeling, Nicolas Corradi, Fred S Dietrich, Sylvia Doan, Joseph HeitmanAbstract:Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the Microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that Microsporidia share a particularly close evolutionary relationship with the zygomycetes.Here we expanded this analysis and also examined a putative sex-locus for variability between Microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the Microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and Microsporidians. One locus previously found to be conserved in many Microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sex-related locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According to sequence-based phylogenetic analyses, the TPT and RNA helicase genes flanking the HMG genes are paralogous rather than orthologous between zygomycetes and Microsporidians.The unique genomic hallmarks between Microsporidia and fungi are independent of sequence based phylogenetic comparisons and further contribute to define the borders of the fungal kingdom and support the classification of Microsporidia as unusual derived fungi. And the sex/sex-related loci appear to have been subject to frequent gene conversion and translocations in Microsporidia and zygomycetes
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Microsporidia evolved from ancestral sexual fungi
Current Biology, 2008Co-Authors: Soo Chan Lee, Patrick J. Keeling, Nicolas Corradi, Edmond J Byrnes, Santiago Torresmartinez, Fred S Dietrich, Joseph HeitmanAbstract:Microsporidia are obligate, intracellular eukaryotic pathogens that infect animal cells, including humans [1]. Previous studies suggested Microsporidia share a common ancestor with fungi [2-7]. However, the exact nature of this phylogenetic relationship is unclear because of unusual features of Microsporidial genomes, which are compact with fewer and highly divergent genes [8]. As a consequence, it is unclear whether Microsporidia evolved from a specific fungal lineage, or whether Microsporidia are a sister group to all fungi. Here, we present evidence addressing this controversial question that is independent of sequence-based phylogenetic reconstruction, but rather based on genome structure. In the zygomycete basal fungal lineage, the sex locus is a syntenic gene cluster governing sexual reproduction in which a high mobility group (HMG) transcription-factor gene is flanked by triose-phosphate transporter (TPT) and RNA helicase genes [9]. Strikingly, Microsporidian genomes harbor a sex-related locus with the same genes in the same order. Genome-wide synteny analysis reveals multiple other loci conserved between Microsporidia and zygomycetes to the exclusion of all other fungal lineages with sequenced genomes. These findings support the hypothesis that Microsporidia are true fungi that descended from a zygomycete ancestor and suggest Microsporidia may have an extant sexual cycle.
Jeremy K Herren - One of the best experts on this subject based on the ideXlab platform.
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a Microsporidian impairs plasmodium falciparum transmission in anopheles arabiensis mosquitoes
Nature Communications, 2020Co-Authors: Jeremy K Herren, Lilian Mbaisi, Enock Mararo, Edward Edmond Makhulu, Victor A Mobegi, Hellen Butungi, Maria Vittoria ManciniAbstract:A possible malaria control approach involves the dissemination in mosquitoes of inherited symbiotic microbes to block Plasmodium transmission. However, in the Anopheles gambiae complex, the primary African vectors of malaria, there are limited reports of inherited symbionts that impair transmission. We show that a vertically transmitted Microsporidian symbiont (Microsporidia MB) in the An. gambiae complex can impair Plasmodium transmission. Microsporidia MB is present at moderate prevalence in geographically dispersed populations of An. arabiensis in Kenya, localized to the mosquito midgut and ovaries, and is not associated with significant reductions in adult host fecundity or survival. Field-collected Microsporidia MB infected An. arabiensis tested negative for P. falciparum gametocytes and, on experimental infection with P. falciparum, sporozoites aren’t detected in Microsporidia MB infected mosquitoes. As a microbe that impairs Plasmodium transmission that is non-virulent and vertically transmitted, Microsporidia MB could be investigated as a strategy to limit malaria transmission. Mircobial symbionts of mosquitoes can affect transmission of human pathogens. Here, Herren et al. identify a Microsporidian symbiont in Anopheles gambiae that impairs transmission without affecting mosquito fecundity or survival.