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Paola Bonfante - One of the best experts on this subject based on the ideXlab platform.
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the mosaic architecture of nrps pks in the arbuscular mycorrhizal fungus Gigaspora Margarita shows a domain with bacterial signature
Frontiers in Microbiology, 2020Co-Authors: Francesco Venice, Alessandra Salvioli, Alessandro Desiro, Gladstone Alves Da Silva, Paola BonfanteAbstract:As obligate biotrophic symbionts, arbuscular mycorrhizal fungi (AMF) live in association with most land plants. Among them, Gigaspora Margarita has been deeply investigated because of its peculiar features, i.e., the presence of an intracellular microbiota with endobacteria and viruses. The genome sequencing of this fungus revealed the presence of some hybrid non-ribosomal peptide synthases-polyketide synthases (NRPS-PKS) that have been rarely identified in AMF. The aim of this study is to describe the architecture of these NRPS-PKS sequences and to understand whether they are present in other fungal taxa related to G. Margarita. A phylogenetic analysis shows that the ketoacyl synthase (KS) domain of one G. Margarita NRPS-PKS clusters with prokaryotic sequences. Since horizontal gene transfer (HGT) has often been advocated as a relevant evolutionary mechanism for the spread of secondary metabolite genes, we hypothesized that a similar event could have interested the KS domain of the PKS module. The bacterial endosymbiont of G. Margarita, Candidatus Glomeribacter Gigasporarum (CaGg), was the first candidate as a donor, since it possesses a large biosynthetic cluster involving an NRPS-PKS. However, bioinformatics analyses do not confirm the hypothesis of a direct HGT from the endobacterium to the fungal host: indeed, endobacterial and fungal sequences show a different evolution and potentially different donors. Lastly, by amplifying a NRPS-PKS conserved fragment and mining the sequenced AMF genomes, we demonstrate that, irrespective of the presence of CaGg, G. Margarita, and some other related Gigasporaceae possess such a sequence.
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Gigaspora Margarita and its endobacterium modulate symbiotic marker genes in tomato roots under combined water and nutrient stress
Plants (Basel Switzerland), 2020Co-Authors: Matteo Chialva, Mara Novero, Luisa Lanfranco, Gianluca Guazzotti, Veronica Santoro, Paola BonfanteAbstract:As members of the plant microbiota, arbuscular mycorrhizal fungi (AMF) may be effective in enhancing plant resilience to drought, one of the major limiting factors threatening crop productivity. AMF host their own microbiota and previous data demonstrated that endobacteria thriving in Gigaspora Margarita modulate fungal antioxidant responses. Here, we used the G. Margarita–Candidatus Glomeribacter Gigasporarum system to test whether the tripartite interaction between tomato, G. Margarita and its endobacteria may improve plant resilience to combined water/nutrient stress. Tomato plants were inoculated with spores containing endobacteria (B+) or not (B-), and exposed to combined water/nutrient stress. Plants traits, AM colonization and expression of AM marker genes were measured. Results showed that mycorrhizal frequency was low and no growth effect was observed. Under control conditions, B+ inoculated plants were more responsive to the symbiosis, as they showed an up-regulation of three AM marker genes involved in phosphate and lipids metabolism compared with B− inoculated or not-inoculated plants. When combined stress was imposed, the difference between fungal strains was still evident for one marker gene. These results indicate that the fungal endobacteria finely modulate plant metabolism, even in the absence of growth response.
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different genetic sources contribute to the small rna population in the arbuscular mycorrhizal fungus Gigaspora Margarita
Frontiers in Microbiology, 2020Co-Authors: Alessandro Silvestri, Francesco Venice, Massimo Turina, Paola Bonfante, Valentina Fiorilli, Laura Miozzi, Luisa LanfrancoAbstract:RNA interference (RNAi) is a key regulatory pathway of gene expression in almost all eukaryotes. This mechanism relies on short non-coding RNA molecules (sRNAs) to recognize in a sequence-specific manner DNA or RNA targets leading to transcriptional or post-transcriptional gene silencing. To date, the fundamental role of sRNAs in the regulation of development, stress responses, defense against viruses and mobile elements, and cross-kingdom interactions has been extensively studied in a number of biological systems. However, the knowledge of the "RNAi world" in arbuscular mycorrhizal fungi (AMF) is still limited. AMF are obligate mutualistic endosymbionts of plants, able to provide several benefits to their partners, from improved mineral nutrition to stress tolerance. Here we described the RNAi-related genes of the AMF Gigaspora Margarita and characterized, through sRNA sequencing, its complex small RNAome, considering the possible genetic sources and targets of the sRNAs. G. Margarita indeed is a mosaic of different genomes since it hosts endobacteria, RNA viruses, and non-integrated DNA fragments corresponding to mitovirus sequences. Our findings show that G. Margarita is equipped with a complete set of RNAi-related genes characterized by the expansion of the Argonaute-like (AGO-like) gene family that seems a common trait of AMF. With regards to sRNAs, we detected populations of sRNA reads mapping to nuclear, mitochondrial, and viral genomes that share similar features (25-nt long and 5'-end uracil read enrichments), and that clearly differ from sRNAs of endobacterial origin. Furthermore, the annotation of nuclear loci producing sRNAs suggests the occurrence of different sRNA-generating processes. In silico analyses indicate that the most abundant G. Margarita sRNAs, including those of viral origin, could target transcripts in the host plant, through a hypothetical cross-kingdom RNAi.
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Metabolome changes are induced in the arbuscular mycorrhizal fungus Gigaspora Margarita by germination and by its bacterial endosymbiont
Mycorrhiza, 2018Co-Authors: Stephen P. Dearth, Francesco Venice, Mara Novero, Paola Bonfante, Hector F. Castro, Eric D. Tague, Shawn Robert CampagnaAbstract:Metabolomic profiling is becoming an increasingly important technique in the larger field of systems biology by allowing the simultaneous measurement of thousands of small molecules participating in and resulting from cellular reactions. In this way, metabolomics presents an opportunity to observe the physiological state of a system, which may provide the ability to monitor the whole of cellular metabolism as the technology progresses. The arbuscular mycorrhizal fungus Gigaspora Margarita has not previously been explored with regard to metabolite composition. To develop a better understanding of G. Margarita and the influences of its endosymbiont Candidatus Glomeribacter Gigasporarum, a metabolomic analysis was applied to quiescent and germinated spores with and without endobacteria. Over 100 metabolites were identified and greater than 2600 unique unidentified spectral features were observed. Multivariate analysis of the metabolomes was performed, and a differentiation between all metabolic states of spores and spores hosting the endobacteria was observed. The known metabolites were recruited to many biochemical pathways, with many being involved in maintenance of the antioxidant potential, tyrosine metabolism, and melanin production. Each of the pathways had higher metabolite abundances in the presence of the endosymbiont. These metabolomics data also agree with previously reported transcriptomics results demonstrating the capability of this technique to confirm hypotheses and showing the feasibility of multi-omic approaches for the study of arbuscular mycorrhizal fungi and their endobacterial communities. Challenges still exist in metabolomic analysis, e.g., the identification of compounds is demanding due to incomplete libraries. A metabolomics technique to probe the effects of bacterial endosymbionts on fungal physiology is presented herein, and this method is useful for hypothesis generation as well as testing as noted above.
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The virome of the arbuscular mycorrhizal fungus Gigaspora Margarita reveals the first report of DNA fragments corresponding to replicating non‐retroviral RNA viruses in fungi
Environmental Microbiology, 2018Co-Authors: Massimo Turina, Stefano Ghignone, Nausicaa Astolfi, Paola Bonfante, Alessandro Silvestri, Luisa LanfrancoAbstract:: Arbuscular Mycorrhizal Fungi (AMF) are key components of the plant microbiota. AMF genetic complexity is increased by the presence of endobacteria, which live inside many species. A further component of such complexity is the virome associated to AMF, whose knowledge is still very limited. Here, by exploiting transcriptomic data we describe the virome of Gigaspora Margarita. A BLAST search for viral RNA-dependent RNA polymerases sequences allowed the identification of four mitoviruses, one Ourmia-like narnavirus, one Giardia-like virus, and two sequences related to Fusarium graminearum mycoviruses. Northern blot and RT-PCR confirmed the authenticity of all the sequences with the exception of the F. graminearum-related ones. All the mitoviruses are replicative and functional since both positive strand and negative strand RNA are present. The abundance of the viral RNA molecules is not regulated by the presence or absence of Candidatus Glomeribacter Gigasporarum, the endobacterium hosted by G. Margarita, with the exception of the Ourmia-like sequence which is absent in bacteria-cured spores. In addition, we report, for the first time, DNA fragments corresponding to mitovirus sequences associated to the presence of viral RNA. These sequences are not integrated in the mitochondrial DNA and preliminary evidence seems to exclude integration in the nuclear genome.
Masanori Saito - One of the best experts on this subject based on the ideXlab platform.
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ph measurement of tubular vacuoles of an arbuscular mycorrhizal fungus Gigaspora Margarita
Mycorrhiza, 2015Co-Authors: Rintaro Funamoto, Katsuharu Saito, Hiroshi Oyaizu, Toshihiro Aono, Masanori SaitoAbstract:Arbuscular mycorrhizal fungi play an important role in phosphate supply to the host plants. The fungal hyphae contain tubular vacuoles where phosphate compounds such as polyphosphate are accumulated. Despite their importance for the phosphate storage, little is known about the physiological properties of the tubular vacuoles in arbuscular mycorrhizal fungi. As an indicator of the physiological state in vacuoles, we measured pH of tubular vacuoles in living hyphae of arbuscular mycorrhizal fungus Gigaspora Margarita using ratio image analysis with pH-dependent fluorescent probe, 6-carboxyfluorescein. Fluorescent images of the fine tubular vacuoles were obtained using a laser scanning confocal microscope, which enabled calculation of vacuolar pH with high spatial resolution. The tubular vacuoles showed mean pH of 5.6 and a pH range of 5.1–6.3. These results suggest that the tubular vacuoles of arbuscular mycorrhizal fungi have a mildly acidic pH just like vacuoles of other fungal species including yeast and ectomycorrhizal fungi.
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influence of nitrogen and phosphorus on polyphosphate accumulation in Gigaspora Margarita during spore germination
Plant and Soil, 2010Co-Authors: Qing Yao, Ryo Ohtomo, Masanori SaitoAbstract:Polyphosphate (polyP) is the form in which phosphorus (P) is transferred from extraradical hyphae into arbuscles in the symbiotic stage of arbuscular mycorrhizal fungi. However, polyP dynamics in the presymbiotic stage are less understood. In this study, we aimed to investigate polyP accumulation in Gigaspora Margarita as influenced by nitrogen (N) and/or P supply during germination. Spores of G. Margarita were incubated on medium with or without P or N addition. PolyP content in the fungal tissue was monitored using a polyP kinase/luciferase system, and polyP synthetic activity was determined with 32P labeling. The results showed that both N and P were necessary for polyP accumulation in germ tubes. Nitrate increased the polyP content in germ tubes, but ammonium did not. Along with germination, polyP content decreased in spores, but increased in germ tubes. 32P labeling indicated that polyP synthetic activity increased in germ tubes along with germination, but was negligible in spores. Our results suggest that, in the presymbiotic stage of G. Margarita, uptake of environmental N and P increases polyP content in germ tubes, and that polyP synthesis occurs mainly therein, leading to polyP accumulation. The possible mechanism of transfer of polyP from spores to hyphae remains to be elucidated.
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application of a molecular method for the identification of a Gigaspora Margarita isolate released in a field
Soil Science and Plant Nutrition, 2005Co-Authors: Kazuhira Yokoyama, Masanori Saito, Takahiro Tateishi, Takuya MarumotoAbstract:A molecular technique for the identification of the Gigaspora Margarita isolate CK based on the detection of a DNA sequence of 235 bp as its diagnostic marker was evaluated to investigate the survival and establishment of introduced arbuscular mycorrizal fungi (AMF) in a field ecosystem. In March 2001, roots and rhizosphere soil of Eragrostis curvula and Miscanthus sinensis were collected from the Mizunashi River at Mt. Fugendake (Nagasaki Prefecture, Japan), where plant seeds and AMF including G. Margarita CK had been introduced for reforestation after the occurrence of repeated pyroclastic flows. We detected the marker sequence from DNA preparations of E. curvula roots and Gigaspora spores in the rhizosphere. This clearly showed that the isolate occurred at both hyphal and sporal stages. It was shown that the isolate survived and developed a life cycle in the revegetation area for 4 years. It was confirmed that the method was effective for tracing the isolate in samples collected from field ecosystems.
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possible involvement of hyphal phosphatase in phosphate efflux from intraradical hyphae isolated from mycorrhizal roots colonized by Gigaspora Margarita
Fungal Biology, 2004Co-Authors: Tomoko Kojima, Masanori SaitoAbstract:We developed a method for separating physiologically active intraradical hyphae of arbuscular mycorrhizal (AM) fungi from mycorrhizal roots, allowing the hyphae to be used for physiological and biochemical experiments. In the present study, the phosphate efflux from the intraradical hyphae in vitro was examined in relation to hyphal phosphatase activity. Onion seedlings ( Allium cepa ) were planted in the soil inoculated with Gigaspora Margarita. Six weeks after transplanting, the intraradical hyphae were isolated from the mycorrhizal roots using plant cell-wall digestion enzymes. The hyphae were incubated briefly at 25 °C in a buffer solution (50 mM Tris/HCl, pH 7.4), then incubated for 2 h and gently shaken with various inhibitors. Phosphate efflux, the amount of phosphate released to the buffer, was analysed by EnzChek phosphate assay kit. Hyphal phosphatase activity was stained histochemically and the proportion of phosphatase-active arbuscules was examined for each inhibitor. Phosphate effluxes were to some degree reduced by all inhibitors used, while the phosphatase inhibitor, BeSO 4 , greatly reduced the efflux. The degree of inhibition in the arbuscular phosphatase by each chemical was closely correlated to the decrease in the phosphate efflux. These results suggest that hyphal phosphatase may be partially involved in the phosphate efflux process from intraradical hyphae.
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acidic vesicles in living hyphae of an arbuscular mycorrhizal fungus Gigaspora Margarita
Plant and Soil, 2004Co-Authors: Katsuharu Saito, Yukari Kugauetake, Masanori SaitoAbstract:Localization and movement of organelles in living hyphae of an arbuscular mycorrhizal fungus, Gigaspora Margarita, were observed using a combination of fluorescent probes and laser-scanning confocal microscopy. Dense, evenly distributed acidic vesicles were visible in germ tubes and extraradical hyphae using DIC with the fluorescent acidotropic probe LysoTracker. These vesicles were distinct from both tubular vacuoles stained with DFFDA and lipid bodies stained with BODIPY 493/503 or Nile Red. Tubular vacuole bundles appeared to be influenced by the bidirectional cytoplasmic streaming of acidic vesicles and lipid bodies. Movement of the acidic vesicles occurred bidrectionally at different rates. The size and distribution of lipid bodies were variable. Based on our observations, the function of these organelles is discussed in relation to nutrient translocation in arbuscular mycorrhizas.
Yves Piche - One of the best experts on this subject based on the ideXlab platform.
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responses of an arbuscular mycorrhizal fungus Gigaspora Margarita to exudates and volatiles from the ri t dna transformed roots of nonmycorrhizal and mycorrhizal mutants of pisum sativum l sparkle
Experimental Mycology, 1995Co-Authors: Boovaraghan Balaji, Horst Vierheilig, Marie Josee Poulin, Yves PicheAbstract:Abstract Balaji, B., Poulin, M. J., Vierheilig, H., and Piche Y. 1995. Responses of an arbuscular mycorrhizal fungus, Gigaspora Margarita , to exudates and volatiles from the Ri T-DNA-transformed roots of nonmycorrhizal and mycorrhizal mutants of Pisum sativum L Sparkle. Experimental Mycology 19, 275-283. Transformed root cultures were established from the nonmycorrhizal (Myc - ) and mycorrhizal (Myc + ) Pisum sativum L Sparkle mutants to study the biochemical factors necessary for initiating and maintaining the arbuscular mycorrhizal (AM) symbiosis. Root exudates produced by both the Myc - and the Myc + mutants inhibited the hyphal growth of Gigaspora Margarita , whereas root volatiles from these mutants stimulated the hyphal growth significantly in the precolonization stage. Carbon dioxide is the principal volatile compound necessary for the elongation of hyphae from both the Myc - and the Myc + transformed roots. The addition of quercetin, a flavonol compound, to the medium with a Myc - mutant enriched with an optimal CO 2 improved hyphal elongation and spreading as previously reported but did not cause Myc - roots to become mycorrhizal. These results suggest that the root factors may stimulate or inhibit AM fungal growth and that they do not determine the mycorrhizal nature of P. sativum Sparkle mutants.
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pisum sativum mutants insensitive to nodulation are also insensitive to invasion in vitro by the mycorrhizal fungus Gigaspora Margarita
Plant Science, 1994Co-Authors: Boovaraghan Balaji, Thomas A Larue, David Tepfer, Yves PicheAbstract:Abstract Transformed root cultures were established using Agrobacterium rhizigenes inoculation of pea mutants, altered in their interaction with Rhizobium . They were tested in an in vitro model for sensitivity to the vesicular-arbuscular mycorrhizal (VAM) fungus, Gigaspora Margarita . VAM development was assessed using light and electron microscopy. Two non-nodulating, non-nitrogen fixing (Nod − , Fix − ) pea mutants were resistant to VAM colonization in vitro: Mycelium developed on the root surface but failed to colonize the interior. A nodulating (Nod + ) genotype, which was unable to fix nitrogen (Fix − ) in association with Rhizobium and a parental line, Lincoln (Nod + , Fix + ), interacted normally with the fungus, showing extensive internal colonization. These results confirm, under axenic conditions, previous reports showing that defective nodulation is correlated with defective mycorrhization. We propose using this in vitro model to identify factors necessary to initiating and maintaining the VAM/plant symbiosis.
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hyphal growth promotion in vitro of the va mycorrhizal fungus Gigaspora Margarita becker hall by the activity of structurally specific flavonoid compounds under co2 enriched conditions
New Phytologist, 1992Co-Authors: S Chabot, R Belrhlid, Robert Chenevert, Yves PicheAbstract:summary Plant phenolic compounds are known to be inducers of virulence genes in plant-pathogen interactions such as those involving Agrobacterium, and flavonoids are known to be inducers or inhibitors of Nod genes in Rhizobium-legume symbiosis. More recent studies suggest that some of these compounds act as molecular signals in the development of vesicular-arbuscular mycorrhizas (VAM). The present study has shown that hyphal growth of the VAM fungus, Gigaspora Margarita Becker & Hall, is affected by both stimulatory and inhibitory flavonoids, when applied at 10 μ together with an optimal carbon dioxide enrichment. Stimulatory compounds were all flavonols (kaempferol, quercetin and morin) and possessed at least one hydroxyl group on the B ring. Conversely, two isoflavones (biochanin A, and genistein), a single flavanone (hesperetin) and two compounds without any hydroxyl group on the B ring, galangin (flavonol) and chrysin (flavone), were all inhibitors of hyphal growth.
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root factors stimulate 32p uptake and plasmalemma atpase activity in vesicular arbuscular mycorrhizal fungus Gigaspora Margarita
New Phytologist, 1991Co-Authors: Jiyu Lei, G Beard, J G Catford, Yves PicheAbstract:summary Root-inducing (Ri) T-DNA transformed roots of carrot were used as the plant partner in a study of 32P absorption and plasmalemma ATPase activity in the hyphae of the vesicular-arbuscular mycorrhizal fungus Gigaspora Margarita Becker & Hall. Hyphae from germinating spores were grown in the presence or absence of root exudates and volatiles. In the presence of these root factors, 32P isotope labelling occurred in hyphae, auxiliary cells and spores, while in the absence of these factors, the labelling only occurred in fungal spores. Similarly, ATPase activity appeared on the fungal plasmalemma only in the presence of root factors. The use of the ATPase inhibitor, diethylstilbestrol, demonstrated the importance of plasmalemma ATPase in the stimulation of hyphal growth of this obligately biotrophic fungus.
Luisa Lanfranco - One of the best experts on this subject based on the ideXlab platform.
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Gigaspora Margarita and its endobacterium modulate symbiotic marker genes in tomato roots under combined water and nutrient stress
Plants (Basel Switzerland), 2020Co-Authors: Matteo Chialva, Mara Novero, Luisa Lanfranco, Gianluca Guazzotti, Veronica Santoro, Paola BonfanteAbstract:As members of the plant microbiota, arbuscular mycorrhizal fungi (AMF) may be effective in enhancing plant resilience to drought, one of the major limiting factors threatening crop productivity. AMF host their own microbiota and previous data demonstrated that endobacteria thriving in Gigaspora Margarita modulate fungal antioxidant responses. Here, we used the G. Margarita–Candidatus Glomeribacter Gigasporarum system to test whether the tripartite interaction between tomato, G. Margarita and its endobacteria may improve plant resilience to combined water/nutrient stress. Tomato plants were inoculated with spores containing endobacteria (B+) or not (B-), and exposed to combined water/nutrient stress. Plants traits, AM colonization and expression of AM marker genes were measured. Results showed that mycorrhizal frequency was low and no growth effect was observed. Under control conditions, B+ inoculated plants were more responsive to the symbiosis, as they showed an up-regulation of three AM marker genes involved in phosphate and lipids metabolism compared with B− inoculated or not-inoculated plants. When combined stress was imposed, the difference between fungal strains was still evident for one marker gene. These results indicate that the fungal endobacteria finely modulate plant metabolism, even in the absence of growth response.
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different genetic sources contribute to the small rna population in the arbuscular mycorrhizal fungus Gigaspora Margarita
Frontiers in Microbiology, 2020Co-Authors: Alessandro Silvestri, Francesco Venice, Massimo Turina, Paola Bonfante, Valentina Fiorilli, Laura Miozzi, Luisa LanfrancoAbstract:RNA interference (RNAi) is a key regulatory pathway of gene expression in almost all eukaryotes. This mechanism relies on short non-coding RNA molecules (sRNAs) to recognize in a sequence-specific manner DNA or RNA targets leading to transcriptional or post-transcriptional gene silencing. To date, the fundamental role of sRNAs in the regulation of development, stress responses, defense against viruses and mobile elements, and cross-kingdom interactions has been extensively studied in a number of biological systems. However, the knowledge of the "RNAi world" in arbuscular mycorrhizal fungi (AMF) is still limited. AMF are obligate mutualistic endosymbionts of plants, able to provide several benefits to their partners, from improved mineral nutrition to stress tolerance. Here we described the RNAi-related genes of the AMF Gigaspora Margarita and characterized, through sRNA sequencing, its complex small RNAome, considering the possible genetic sources and targets of the sRNAs. G. Margarita indeed is a mosaic of different genomes since it hosts endobacteria, RNA viruses, and non-integrated DNA fragments corresponding to mitovirus sequences. Our findings show that G. Margarita is equipped with a complete set of RNAi-related genes characterized by the expansion of the Argonaute-like (AGO-like) gene family that seems a common trait of AMF. With regards to sRNAs, we detected populations of sRNA reads mapping to nuclear, mitochondrial, and viral genomes that share similar features (25-nt long and 5'-end uracil read enrichments), and that clearly differ from sRNAs of endobacterial origin. Furthermore, the annotation of nuclear loci producing sRNAs suggests the occurrence of different sRNA-generating processes. In silico analyses indicate that the most abundant G. Margarita sRNAs, including those of viral origin, could target transcripts in the host plant, through a hypothetical cross-kingdom RNAi.
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The virome of the arbuscular mycorrhizal fungus Gigaspora Margarita reveals the first report of DNA fragments corresponding to replicating non‐retroviral RNA viruses in fungi
Environmental Microbiology, 2018Co-Authors: Massimo Turina, Stefano Ghignone, Nausicaa Astolfi, Paola Bonfante, Alessandro Silvestri, Luisa LanfrancoAbstract:: Arbuscular Mycorrhizal Fungi (AMF) are key components of the plant microbiota. AMF genetic complexity is increased by the presence of endobacteria, which live inside many species. A further component of such complexity is the virome associated to AMF, whose knowledge is still very limited. Here, by exploiting transcriptomic data we describe the virome of Gigaspora Margarita. A BLAST search for viral RNA-dependent RNA polymerases sequences allowed the identification of four mitoviruses, one Ourmia-like narnavirus, one Giardia-like virus, and two sequences related to Fusarium graminearum mycoviruses. Northern blot and RT-PCR confirmed the authenticity of all the sequences with the exception of the F. graminearum-related ones. All the mitoviruses are replicative and functional since both positive strand and negative strand RNA are present. The abundance of the viral RNA molecules is not regulated by the presence or absence of Candidatus Glomeribacter Gigasporarum, the endobacterium hosted by G. Margarita, with the exception of the Ourmia-like sequence which is absent in bacteria-cured spores. In addition, we report, for the first time, DNA fragments corresponding to mitovirus sequences associated to the presence of viral RNA. These sequences are not integrated in the mitochondrial DNA and preliminary evidence seems to exclude integration in the nuclear genome.
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endobacteria affect the metabolic profile of their host Gigaspora Margarita an arbuscular mycorrhizal fungus
Environmental Microbiology, 2010Co-Authors: Alessandra Salvioli, Luisa Lanfranco, Marco Chiapello, Joel Fontaine, Anissa Lounes Hadjsahraoui, Anne Grandmouginferjani, Paola BonfanteAbstract:4 IPP-CNR, Torino, Italy. Summary The aim of this paper was to understand whether the endobacterium identified as Candidatus Glomerib- acter Gigasporarum has an effect on the biology of its host, the arbuscular mycorrhizal fungus Gigaspora Margarita, through the study of the modifications induced on the fungal proteome and lipid profile. The availability of G. Margarita cured spores (i.e. spores that do not contain bacteria), represented a crucial tool to enable the comparison between two fungal homogeneous populations in the presence and the absence of the bacterial components. Our results demonstrate that the endobacterial presence leads to a modulation of fungal protein expression in all the different conditions we tested (quiescent, germinat- ing and strigolactone-elicited germinating spores), and in particular after treatment with a strigolactone analogue. The fungal fatty acid profile resulted to be modified both quantitatively and qualitatively in the absence of endobacteria, being fatty acids less abun- dant in the cured spores. The results offer one of the first comparative metabolic studies of an AM fungus investigated under different physiological conditions, reveal that endobacteria have an important impact on the host fungal activity, influencing both protein expression and lipid profile, and suggest that the bac- terial absence is perceived by G. Margarita as a stimulus which activates stress-responsive proteins.
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enhanced activity of the gmarmt1 promoter from the mycorrhizal fungus Gigaspora Margarita at limited carbon supply
Fungal Genetics and Biology, 2007Co-Authors: Roberta Bergero, Stefano Ghignone, Luisa Lanfranco, Paola BonfanteAbstract:Metallothioneins are low molecular weight polypeptides, present in most eukaryotic phyla, with role in metal homeostasis and detoxification. We previously reported the identification and the characterization of a metallothionein gene (GmarMT1) from the arbuscular mycorrhizal fungus Gigaspora Margarita. Here, we have used real-time quantitative RT-PCR to show that GmarMT1 expression was turned off during the symbiotic fungal growth in the hexose-rich mycorrhizal apoplast, whereas transcripts were abundant during all other fungal growth stages, when products of lipid breakdown and the glyoxylate cycle feed carbohydrate-consuming pathways. In support of a nutritional regulation of GmarMT1 expression, we show that transcriptional activity of GmarMT1 promoter in yeast was strongly induced by glucose starvation (up to 20 times the basal level). We speculate that GmarMT1-encoded protein, with its proved metal binding ability, could regulate the homeostasis of zinc, a fundamental cofactor involved in C metabolism regulation and glucose repression.
Tadao Wagatsuma - One of the best experts on this subject based on the ideXlab platform.
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Formation of appressoria by the arbuscular mycorrhizal fungus Gigaspora Margarita on roots of Allium cepa is linked with root age
Mycoscience, 2007Co-Authors: Keitaro Tawaraya, Shigeki Watanabe, Horst Vierheilig, Tadao WagatsumaAbstract:Spores of the arbuscular mycorrhizal fungus, Gigaspora Margarita, were placed near the root tip, the middle of the root (equal distance from root base and root tip), or the root base (close to the shoot) of the first primary root of 9-day-old onion. Two weeks later, the number and position of appressoria and the appressoria with penetrating hyphae were determined in the first and the newly formed second primary roots. The total number of appressoria was not significantly different among the treatments. Inoculation near the root tip of the first primary root resulted in the formation of a large number of appressoria on the first primary root and the formation of about three times fewer appressoria on the second primary root. Inoculation near the base of the first primary root resulted in the formation of no appressoria on the first primary root, whereas many appressoria were formed on the second primary root. Our results suggest that the root age is a determinant of the appressorium formation.
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inhibition of pre symbiotic hyphal growth of arbuscular mycorrhizal fungus Gigaspora Margarita by root exudates of lupinus spp
Soil Science and Plant Nutrition, 2002Co-Authors: Hirosuke Oba, Keitaro Tawaraya, Tadao WagatsumaAbstract:Abstract Effect of root exudates of Lupinus plants on hyphal growth of arbuscular mycorrhizal (AM) fungus was investigated in order to elucidate the failure of mycorrhizal colonization in nonhost plants. Four species of Lupinus were grown in solution culture and root exudates were collected. Spores of Gigaspora Margarita were incubated with the root exudates. Hyphal length in the root exudates of L. luteus, L. aridus, and L. cosentini was shorter than that of the control treatment, irrespective of the P status of Lupinus plants. Numbers of hyphae exhibiting branching were lower in the root exudates of L. luteus and L. cosentini than in those of the controls. It is suggested that these Lupinus plants did not induce pre-symbiotic hyphal growth of AM fungi but inhibited it.
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effect of root exudate fractions from p deficient and p sufficient onion plants on root colonisation by the arbuscular mycorrhizal fungus Gigaspora Margarita
Mycorrhiza, 1998Co-Authors: Keitaro Tawaraya, Kazuko Hashimoto, Tadao WagatsumaAbstract:The effect of root exudates from P-deficient onion on root colonisation by an arbuscular mycorrhizal fungus was examined. Onions (Allium cepa L.) were grown in solution culture at phosphorus concentrations of 0 (P0) and 2 (P2) mg P l–1. Root exudates were collected and fractionated with Amberlite XAD-4 resin to give EtOH and water soluble fractions. Onions inoculated with the arbuscular mycorrhizal fungus Gigaspora Margarita Becker & Hall were grown with or without (control) root exudates and exudate fractions in a growth chamber. After 24 days, arbuscular mycorrhiza levels and appressoria formation had increased in plants treated with P0-root exudate or the P0-EtOH fraction when compared to corresponding P2 treatments or control plants. P0 and P2 water-soluble fractions did not significantly affect either aspect of fungal development. These results suggest that hydrophobic compounds found in root exudates from P-deficient onion increase appressorium formation and, therefore, enhance mycorrhiza development.
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effect of onion allium cepa root exudates on the hyphal growth of Gigaspora Margarita
Mycorrhiza, 1995Co-Authors: Keitaro Tawaraya, Shigeki Watanabe, E Yoshida, Tadao WagatsumaAbstract:The effect of root exudates from onions differing in P status on spore germination and hyphal growth of arbuscular mycorrhizal fungi was investigated. Onion (Allium cepa) was grown in solution culture at different phosphorus concentrations (0, 0.1, 1.0, 8.0 and 24.0 mg P l–1) and root exudates were collected. When spores of the arbuscular mycorrhizal fungus, Gigaspora Margarita were incubated with these root exudates, spore germination was only slightly affected but hyphal growth was greatly affected, particularly with exudates from P-deficient plants. This suggests that the P nutrition of host plants influences the composition of root exudates and thereby the hyphal growth of arbuscular mycorrhizal fungi.