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Chembiochem : a European Journal of... Oct 2018The rice seedling blight fungus Rhizopus microsporus harbors endosymbiotic bacteria (Burkholderia rhizoxinica) that produce the virulence factor rhizoxin and control...
The rice seedling blight fungus Rhizopus microsporus harbors endosymbiotic bacteria (Burkholderia rhizoxinica) that produce the virulence factor rhizoxin and control host development. Genome mining indicated a massive inventory of cryptic nonribosomal peptide synthetase (NRPS) genes, which have not yet been linked to any natural products. The discovery and full characterization of a novel cyclopeptide from endofungal bacteria is reported. In silico analysis of an orphan, symbiont-specific NRPS predicted the structure of a nonribosomal peptide, which was targeted by LC-MS/MS profiling of wild-type and engineered null mutants. NMR spectroscopy and chemical derivatization elucidated the structure of the bacterial cyclopeptide. Phylogenetic analyses revealed the relationship of starter C domains for rare N-acetyl-capped peptides. Heptarhizin is produced under symbiotic conditions in geographically constrained strains from the Pacific clade; this indicates a potential ecological role of the peptide.
Topics: Burkholderia; Oryza; Peptide Synthases; Peptides, Cyclic; Plant Diseases; Rhizopus; Seedlings; Symbiosis
PubMed: 30113119
DOI: 10.1002/cbic.201800400 -
Frontiers in Fungal Biology 2022Mucoralean fungi from the genus are common inhabitants of terrestrial ecosystems, being some pathogens of animals and plants. In this study, we analyzed the symbiotic...
Mucoralean fungi from the genus are common inhabitants of terrestrial ecosystems, being some pathogens of animals and plants. In this study, we analyzed the symbiotic and toxinogenic potential of species derived from agricultural soils dedicated to the production of papaya ( L.) in Mexico. Four representative strains of soil-derived spp. were analyzed employing molecular, microscopic, and metabolic methods. The ITS phylogenies identified the fungi as HP499, HP475 and HP479, and HP487. We discovered that HP499 and HP475 harbor similar endofungal bacterial symbionts that belong to the genus ( sensu lato) and that none of the four fungi were associated with RmNV-20S and RmNV-23S. Intriguingly, the interaction between - showed different phenotypes from known - symbioses. Elimination of bacteria in HP475 did not cause a detrimental effect on fungal growth or asexual reproduction. Moreover, metabolic and molecular analyses confirmed that, unlike symbiotic HP499, HP475 does not produce rhizoxin, one of the best-characterized toxins produced by spp. The rhizoxin () biosynthetic gene cluster seems absent in this symbiotic bacterium. Our study highlights that the symbioses between and are more diverse than anticipated. Our findings contribute to expanding our understanding of the role bacterial symbionts have in the pathogenicity, biology and evolution of Mucorales.
PubMed: 37746220
DOI: 10.3389/ffunb.2022.893700 -
Current Medicinal Chemistry 2008Despite the conventional and high-dose chemotherapy with hematopoietic stem cell transplantation, multiple myeloma eventually relapses, resulting in an incurable... (Review)
Review
Despite the conventional and high-dose chemotherapy with hematopoietic stem cell transplantation, multiple myeloma eventually relapses, resulting in an incurable hematological malignancy. Therefore, novel therapeutic approaches in clinical settings are desired. Recently, thalidomide was introduced for the treatment of myeloma, and many clinical trials have since confirmed its efficacy in patients with relapsed/refractory or newly diagnosed multiple myeloma. Multiple mechanisms have been proposed to explain thalidomide's anti-myeloma activity. However, the precise mechanism underlying this activity remains unclear, because thalidomide rapidly undergoes spontaneous, nonenzymatic, hydrolytic cleavage to numerous metabolites in vivo. To elucidate the exact anti-myeloma mechanism of thalidomide in vivo, we have performed structural development studies of thalidomide, and obtained various analogs with specific molecular properties. Among these derivatives, we found that a new thalidomide analog, 2-(2,6-diisopropylphenyl)-5-hydroxy-1H-isoindole-1,3-dione (5HPP-33), has the most potent anti-myeloma effect with tubulin polymerization inhibiting activity. 5HPP-33 directly inhibited the growth and survival of various myeloma cells in a dose-dependent manner with IC(50) of 1-10 microM. In contrast, thalidomide itself did not inhibit RPMI8226 cell growth. A tubulin polymerization assay using microtubule protein from porcine brain revealed that 5HPP-33 had potent tubulin polymerization inhibiting activity with IC(50) of 8.1 microM, comparable to that of rhizoxin, a known tubulin polymerization inhibitor. Moreover, its activity was more potent than that of a known thalidomide metabolite, 5-hydroxythalidomide. Our data suggest that 5HPP-33 is a promising candidate as a therapeutic agent for multiple myeloma. In addition, the results suggest that thalidomide's tubulin polymerization inhibiting activity might be the mechanism underlying the induction of apoptosis in myeloma cells.
Topics: Humans; Multiple Myeloma; Thalidomide; Tubulin Modulators
PubMed: 18393844
DOI: 10.2174/092986708783955473 -
Annals of Oncology : Official Journal... May 1992Phase I studies requiring multiple dose escalation steps have led to the development of pharmacokinetically guided dose escalation (PGDE) strategies to expedite the... (Review)
Review
Phase I studies requiring multiple dose escalation steps have led to the development of pharmacokinetically guided dose escalation (PGDE) strategies to expedite the conduct of early clinical trials. This article critically reviews PGDE strategies for a number of new anticancer agents including amphethinile, brequinar sodium, iodo-doxorubicin, the anthrapyrazoles (DuP 941, DuP 942 and DuP 937), rhizoxin, and aphidicolin glycinate. The benefits and problems associated with PGDE are examined. Recommendations are made for the optimal deployment of pharmacological information in future phase I studies.
Topics: Antineoplastic Agents; Clinical Trials as Topic; Dose-Response Relationship, Drug; Drug Administration Schedule; Drug Evaluation; Forecasting; Humans; Prospective Studies
PubMed: 1616887
DOI: 10.1093/oxfordjournals.annonc.a058203 -
The Journal of Infectious Diseases Oct 2008Environmental isolates of the fungus Rhizopus have been shown to harbor a bacterial endosymbiont (Burkholderia) that produces rhixozin, a plant mycotoxin. We sought to...
Environmental isolates of the fungus Rhizopus have been shown to harbor a bacterial endosymbiont (Burkholderia) that produces rhixozin, a plant mycotoxin. We sought to define the role of rhizoxin production by endosymbionts in the pathogenesis of mucormycosis. Endosymbiotic bacteria were identified by polymerase chain reaction in 15 (54%) of 28 clinical isolates of Zygomycetes, with 33% of the bacterial strains showing 87% identity to Burkholderia 16S rDNA. The presence of rhizoxin in myclial extracts from fungi harboring bacteria was confirmed by high-performance liquid chromatography analysis. However, fungal strains with or without endosymbionts did not differ in their ability to cause endothelial cell injury in vitro, nor did antibiotic-mediated eradication of endosymbionts and rhizoxin production decrease the virulence of fungal strains in mice or flies. In summary, although bacterial endosymbiosis is widely detected in clinical isolates of Zygomycetes, including Rhizopus oryzae strains, we found no evidence that bacterial endosymbionts and rhizoxin contribute to the pathogenesis of mucormycosis in the models studied.
Topics: Animals; Burkholderia; Endothelial Cells; Humans; Macrolides; Male; Mice; Mice, Inbred BALB C; Mucor; Mucormycosis; Rhizopus; Symbiosis
PubMed: 18694335
DOI: 10.1086/591461 -
Access Microbiology 2023Several species of soil-dwelling nematodes are used in the biocontrol of crop pests, due to their natural capacity to kill diverse lepidopteran species. Although this...
Several species of soil-dwelling nematodes are used in the biocontrol of crop pests, due to their natural capacity to kill diverse lepidopteran species. Although this insect-killing trait is known to be augmented by the nematodes' endosymbionts, the role of other steinernematid-associated bacterial genera in the nematode lifecycle remains unclear. This genomic study aimed to determine the potential of to contribute to the entomopathogenicity of its host. Insect larvae were infected with three separate cultures. From each of the three treatments, the prevalent bacteria in the haemocoel of cadavers, four days post-infection, were isolated. These three bacterial isolates were morphologically characterised. DNA was extracted from each of the three bacterial isolates and used for long-read genome sequencing and assembly. Assemblies were used to delineate species and identify genes that encode insect toxins, antimicrobials, and confer antibiotic resistance. We assembled three complete genomes. Through digital DNA-DNA hybridisation analyses, we ascertained that the haemocoels of insect cadavers previously infected with sp. Kalro, sp. 75, and sp. 97 were dominated by Kalro, 75, and 97, respectively. Kalro and 97 formed a subspecies with other symbionts of steinernematids from Kenya. 75 phylogenetically clustered with pseudomonads that are characterised by high insecticidal activity. The 75 genome encoded the production pathway of insect toxins such as orfamides and rhizoxins, antifungals such as pyrrolnitrin and pyoluteorin, and the broad-spectrum antimicrobial 2,4-diacetylphloroglucinol. The 75 genome encoded resistance to over ten classes of antibiotics, including cationic lipopeptides. Steinernematid-associated bacteria hence have the biosynthetic potential to contribute to nematode entomopathogenicity.
PubMed: 37970093
DOI: 10.1099/acmi.0.000659.v3 -
Nature Oct 2005A number of plant pathogenic fungi belonging to the genus Rhizopus are infamous for causing rice seedling blight. This plant disease is typically initiated by an...
A number of plant pathogenic fungi belonging to the genus Rhizopus are infamous for causing rice seedling blight. This plant disease is typically initiated by an abnormal swelling of the seedling roots without any sign of infection by the pathogen. This characteristic symptom is in fact caused by the macrocyclic polyketide metabolite rhizoxin that has been isolated from cultures of Rhizopus sp.. The phytotoxin exerts its destructive effect by binding to rice beta-tubulin, which results in inhibition of mitosis and cell cycle arrest. Owing to its remarkably strong antimitotic activity in most eukaryotic cells, including various human cancer cell lines, rhizoxin has attracted considerable interest as a potential antitumour drug. Here we show that rhizoxin is not biosynthesized by the fungus itself, but by endosymbiotic, that is, intracellular living, bacteria of the genus Burkholderia. Our unexpected findings unveil a remarkably complex symbiotic-pathogenic relationship that extends the fungus-plant interaction to a third, bacterial, key-player, and opens new perspectives for pest control.
Topics: Antibiotics, Antineoplastic; Burkholderia; Cell Extracts; Chromatography, High Pressure Liquid; Lactones; Lasers; Macrolides; Molecular Sequence Data; Molecular Structure; Mycelium; Oryza; Phylogeny; Plant Diseases; Polymerase Chain Reaction; Rhizopus; Symbiosis; Toxins, Biological
PubMed: 16208371
DOI: 10.1038/nature03997 -
Biology of Reproduction Jun 2004Two-cell bovine embryos become arrested in development when exposed to a physiologically relevant heat shock. One of the major ultrastructural modifications caused by...
Two-cell bovine embryos become arrested in development when exposed to a physiologically relevant heat shock. One of the major ultrastructural modifications caused by heat shock is translocation of organelles toward the center of the blastomere. The objective of the present study was to determine if heat- shock-induced movement of organelles is a result of cytoskeletal rearrangement. Two-cell bovine embryos were cultured at 38.5 degrees C (homeothermic temperature of the cow), 41.0 degrees C (physiologically relevant heat shock), or 43.0 degrees C (severe heat shock) for 6 h in the presence of either vehicle, latrunculin B (a microfilament depolymerizer), rhizoxin (a microtubule depolymerizer), or paclitaxel (a microtubule stabilizer). Heat shock caused a rearrangement of actin-containing filaments as detected by staining with phalloidin. Moreover, latrunculin B reduced the heat-shock-induced movement of organelles at 41.0 degrees C but not at 43.0 degrees C. In contrast, movement of organelles caused by heat shock was inhibited by rhizoxin at both temperatures. Furthermore, rhizoxin, but not latrunculin B, reduced the swelling of mitochondria caused by heat shock. Paclitaxel, while causing major changes in ultrastructure, did not prevent the movement of organelles or mitochondrial swelling. It is concluded that heat shock disrupts microtubule and microfilaments in the two-cell bovine embryo and that these changes are responsible for movement of organelles away from the periphery. In addition, intact microtubules are a requirement for heat-shock-induced swelling of mitochondria. Differences in response to rhizoxin and paclitaxel are interpreted to mean that deformation of microtubules can occur through a mechanism independent of microtubule depolymerization.
Topics: Actin Cytoskeleton; Animals; Bridged Bicyclo Compounds, Heterocyclic; Cattle; Cell Nucleus; Cleavage Stage, Ovum; Cytoplasm; Female; Heat-Shock Response; Lactones; Macrolides; Microscopy, Electron; Microtubules; Mitochondrial Swelling; Movement; Paclitaxel; Thiazoles; Thiazolidines
PubMed: 14960486
DOI: 10.1095/biolreprod.103.024901 -
Memorias Do Instituto Oswaldo Cruz Feb 2013The trypanosomatid cytoskeleton is responsible for the parasite's shape and it is modulated throughout the different stages of the parasite's life cycle. When parasites...
The trypanosomatid cytoskeleton is responsible for the parasite's shape and it is modulated throughout the different stages of the parasite's life cycle. When parasites are exposed to media with reduced osmolarity, they initially swell, but subsequently undergo compensatory shrinking referred to as regulatory volume decrease (RVD). We studied the effects of anti-microtubule (Mt) drugs on the proliferation of Leishmania mexicana promastigotes and their capacity to undergo RVD. All of the drugs tested exerted antiproliferative effects of varying magnitudes [ansamitocin P3 (AP3)> trifluoperazine > taxol > rhizoxin > chlorpromazine]. No direct relationship was found between antiproliferative drug treatment and RVD. Similarly, Mt stability was not affected by drug treatment. Ansamitocin P3, which is effective at nanomolar concentrations, blocked amastigote-promastigote differentiation and was the only drug that impeded RVD, as measured by light dispersion. AP3 induced 2 kinetoplasts (Kt) 1 nucleus cells that had numerous flagella-associated Kts throughout the cell. These results suggest that the dramatic morphological changes induced by AP3 alter the spatial organisation and directionality of the Mts that are necessary for the parasite's hypotonic stress-induced shape change, as well as its recovery.
Topics: Animals; Chlorpromazine; Cytoskeleton; Leishmania mexicana; Macrolides; Maytansine; Mice; Paclitaxel; Trifluoperazine; Tubulin Modulators
PubMed: 23440120
DOI: 10.1590/s0074-02762013000100014 -
Nature Chemical Biology Dec 2015Biosynthesis of rhizoxin in Burkholderia rhizoxinica affords an unusual polyketide synthase module with ketosynthase and branching domains that install the δ-lactone,...
Biosynthesis of rhizoxin in Burkholderia rhizoxinica affords an unusual polyketide synthase module with ketosynthase and branching domains that install the δ-lactone, conferring antimitotic activity. To investigate their functions in chain branching, we designed chimeric modules with structurally similar domains from a glutarimide-forming module and a dehydratase. Biochemical, kinetic and mutational analyses reveal a structural role of the accessory domains and multifarious catalytic actions of the ketosynthase.
Topics: Acyltransferases; Burkholderia; Macrolides; Molecular Conformation; Polyketide Synthases; Polyketides
PubMed: 26479442
DOI: 10.1038/nchembio.1932