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Dianne K Newman - One of the best experts on this subject based on the ideXlab platform.
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extended hopanoid loss reduces bacterial motility and surface attachment and leads to heterogeneity in root nodule growth kinetics in a bradyrhizobium aeschynomene symbiosis
Molecular Plant-microbe Interactions, 2019Co-Authors: Brittany J Belin, E T Tookmanian, J De Anda, Gerard C L Wong, Dianne K NewmanAbstract:Hopanoids are steroid-like bacterial lipids that enhance membrane rigidity and promote bacterial growth under diverse stresses. Hopanoid biosynthesis genes are conserved in nitrogen-fixing Plant Symbionts, and we previously found that the extended (C35) class of hopanoids in Bradyrhizobium diazoefficiens are required for efficient symbiotic nitrogen fixation in the tropical legume host Aeschynomene afraspera. Here, we demonstrate that the nitrogen-fixation defect conferred by extended hopanoid loss can be fully explained by a reduction in root nodule sizes rather than per-bacteroid nitrogen-fixation levels. Using a single-nodule tracking approach to quantify A. afraspera nodule development, we provide a quantitative model of root nodule development in this host, uncovering both the baseline growth parameters for wild-type nodules and a surprising heterogeneity of extended hopanoid mutant developmental phenotypes. These phenotypes include a delay in root nodule initiation and the presence of a subpopulation of nodules with slow growth rates and low final volumes, which are correlated with reduced motility and surface attachment in vitro and lower bacteroid densities in Planta, respectively. This work provides a quantitative reference point for understanding the phenotypic diversity of ineffective Symbionts in A. afraspera and identifies specific developmental stages affected by extended hopanoid loss for future mechanistic work.
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extended hopanoid loss reduces bacterial motility and surface attachment and leads to heterogeneity in root nodule growth kinetics in a bradyrhizobium aeschynomene symbiosis
bioRxiv, 2018Co-Authors: Brittany J Belin, E T Tookmanian, J De Anda, Gerard C L Wong, Dianne K NewmanAbstract:Abstract Hopanoids are steroid-like bacterial lipids that enhance membrane rigidity and promote bacterial growth under diverse stresses. Hopanoid biosynthesis genes are conserved in nitrogen-fixing Plant Symbionts, and we previously found that the extended (C35) class of hopanoids in Bradyrhizobium diazoefficiens are required for efficient symbiotic nitrogen fixation in the tropical legume host Aeschynomene afraspera. Here we demonstrate that the nitrogen fixation defect conferred by extended loss can fully be explained by a reduction in root nodule sizes rather than per-bacteroid nitrogen fixation levels. Using a single-nodule tracking approach to track A. afraspera nodule development, we provide a quantitative model of root nodule development in this host, uncovering both the baseline growth parameters for wild-type nodules and a surprising heterogeneity of extended hopanoid mutant developmental phenotypes. These phenotypes include a delay in root nodule initiation and presence of a subpopulation of nodules with slow growth rates and low final volumes, which are correlated with reduced motility and surface attachment in vitro and lower bacteroid densities in Planta, respectively. This work provides a quantitative reference point for understanding the phenotypic diversity of ineffective Symbionts in A. afraspera and identifies specific developmental stages affected by extended hopanoid loss for future mechanistic work.
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specific hopanoid classes differentially affect free living and symbiotic states of bradyrhizobium diazoefficiens
Mbio, 2015Co-Authors: Gargi Kulkarni, Nicolas Busset, Antonio Molinaro, Daniel Gargani, Clemence Chaintreuil, Alba Silipo, Eric Giraud, Dianne K NewmanAbstract:A better understanding of how bacteria resist stresses encountered during the progression of Plant-microbe symbioses will advance our ability to stimulate Plant growth. Here, we show that the symbiotic system comprising the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens and the legume Aeschynomene afraspera requires hopanoid production for optimal fitness. While methylated (2Me) hopanoids contribute to growth under Plant-cell-like microaerobic and acidic conditions in the free-living state, they are dispensable during symbiosis. In contrast, synthesis of extended (C35) hopanoids is required for growth microaerobically and under various stress conditions (high temperature, low pH, high osmolarity, bile salts, oxidative stress, and antimicrobial peptides) in the free-living state and also during symbiosis. These defects might be due to a less rigid membrane resulting from the absence of free or lipidA-bound C35 hopanoids or the accumulation of the C30 hopanoid diploptene. Our results also show that C35 hopanoids are necessary for symbiosis only with the host Aeschynomene afraspera but not with soybean. This difference is likely related to the presence of cysteine-rich antimicrobial peptides in Aeschynomene nodules that induce drastic modification in bacterial morphology and physiology. The study of hopanoid mutants in Plant Symbionts thus provides an opportunity to gain insight into host-microbe interactions during later stages of symbiotic progression, as well as the microenvironmental conditions for which hopanoids provide a fitness advantage.
Gary E Harman - One of the best experts on this subject based on the ideXlab platform.
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seed treatment with trichoderma harzianum alleviates biotic abiotic and physiological stresses in germinating seeds and seedlings
Phytopathology, 2010Co-Authors: Fatemeh Mastouri, Thomas Bjorkman, Gary E HarmanAbstract:Mastouri, F., Bjorkman, T., and Harman, G. E. 2010. Seed treatment with Trichoderma harzianum alleviates biotic, abiotic, and physiological stresses in germinating seeds and seedlings. Phytopathology 100:12131221. Trichoderma spp. are endophytic Plant Symbionts that are widely used as seed treatments to control diseases and to enhance Plant growth and yield. Although some recent work has been published on their abilities to alleviate abiotic stresses, specific knowledge of mechanisms, abilities to control multiple Plant stress factors, their effects on seed and seedlings is lacking. We examined the effects of seed treatment with T. harzianum strain T22 on germination of seed exposed to biotic stress (seed and seedling disease caused by Pythium ultimum) and abiotic stresses (osmotic, salinity, chilling, or heat stress). We also evaluated the ability of the beneficial fungus to overcome physiological stress (poor seed quality induced by seed aging). If seed were not under any of the stresses noted above, T22 generally had little effect upon seedling performance. However, under stress, treated seed germinated consistently faster and more uniformly than untreated seeds whether the stress was osmotic, salt, or suboptimal temperatures. The consistent response to varying stresses suggests a common mechanism through which the Plant–fungus association enhances tolerance to a wide range of abiotic stresses as well as biotic stress. A common factor that negatively affects Plants under these stress conditions is accumulation of toxic reactive oxygen species (ROS), and we tested the hypothesis that T22 reduced damages resulting from accumulation of ROS in stressed Plants. Treatment of seeds reduced accumulation of lipid peroxides in seedlings under osmotic stress or in aged seeds. In addition, we showed that the effect of exogenous application of an antioxidant, glutathione, or application of T22, resulted in a similar positive effect on seed germination under osmotic stress or in aged seed. This evidence supports the model that T. harzianum strain T22 increases seedling vigor and ameliorates stress by inducing physiological protection in Plants against oxidative damage.
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trichoderma species opportunistic avirulent Plant Symbionts
Nature Reviews Microbiology, 2004Co-Authors: Gary E Harman, Charles R Howell, Ada Viterbo, Ilan Chet, Matteo LoritoAbstract:Trichoderma spp. are free-living fungi that are common in soil and root ecosystems. Recent discoveries show that they are opportunistic, avirulent Plant Symbionts, as well as being parasites of other fungi. At least some strains establish robust and long-lasting colonizations of root surfaces and penetrate into the epidermis and a few cells below this level. They produce or release a variety of compounds that induce localized or systemic resistance responses, and this explains their lack of pathogenicity to Plants. These root–microorganism associations cause substantial changes to the Plant proteome and metabolism. Plants are protected from numerous classes of Plant pathogen by responses that are similar to systemic acquired resistance and rhizobacteria-induced systemic resistance. Root colonization by Trichoderma spp. also frequently enhances root growth and development, crop productivity, resistance to abiotic stresses and the uptake and use of nutrients.
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THE MECHANISMS AND APPLICATIONS OF SYMBIOTIC OPPORTUNISTIC Plant Symbionts
NATO Security through Science Series, 2026Co-Authors: Gary E Harman, Michal ShoreshAbstract:A number of fungi have evolved a symbiotic life style with Plants, including some organisms that include similar strains or species that are Plant pathogens. Some are obligate Symbionts such as ecto- or endomycorrhizal fungi, while others are endophytes that have free-living capabilities. Still oth- ers are highly competitive in soil and proliferate there. These are the oppor- tunistic Plant Symbionts. Fungi in the genus Trichoderma have long been considered as biocontrol agents, but they are highly successful Plant sym- bionts as well. The critical step for establishment of the symbiotic life style begins with root colonization and infection of outer cortical layers. A zone of chemical interaction is established; some of the Trichoderma signaling molecules are known. As a result of this interaction, the fungus is walled off; in rare cases where components of this communication are lacking, Tricho- derma can become a pathogen. The results of this interaction include induced systemic resistance, increased growth responses and yields, and increased nu- trient uptake and fertilizer use efficiency. The interaction induces substantial changes in Plant physiology. In the maize-T. harzianum strain T22 interaction, more than 300 proteins have altered expression, with a number of them being up-regulated. Included in this group are, most notably, enzymes of carbohy- drate metabolism and proteins associated with pathogen resistance and stress. Multiple forms of several proteins are upregulated, including numerous ex- amples of chitinases, β-glucosidases, proteins with nucleotide binding sites and leucine rich repeats associated with resistance to disease, sucrose syn- thase, and methionine synthase. The substantial increases in several of these are highly suggestive of changes in metabolic pathways or regulation.
Nicolas Corradi - One of the best experts on this subject based on the ideXlab platform.
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long reads and hi c sequencing illuminate the two compartment genome of the model arbuscular mycorrhizal symbiont rhizophagus irregularis
bioRxiv, 2021Co-Authors: Gokalp Yildirir, Jana Sperschneider, M C Malar, E C Chen, Wataru Iwasaki, C Cornell, Nicolas CorradiAbstract:Chromosome folding links genome structure with gene function by generating distinct nuclear compartments and topologically associating domains (TADs). In mammals, these domains undergo preferential interactions and regulate gene expression, however in fungi the role of chromosome folding in genome biology is unclear. Here, we combine Nanopore (ONT) sequencing with chromatin conformation capture sequencing (Hi-C) to reveal chromosome diversity in a group of obligate Plant Symbionts with a multinucleate mycelium; the arbuscular mycorrhizal fungi (AMF). We find that phylogenetically distinct strains of the model AMF Rhizophagus irregularis all carry 33 chromosomes. Homologous chromosomes show within species variability in size, as well as in gene and repeat content. Strain-specific Hi-C sequencing reveals that all strains have a 3D genome organization that resembles a checkerboard structure with two distinct (A/B) chromatin compartments. Each compartment differs in the level of gene transcription, regulation of candidate effectors and methylation rate. The A-compartment is more gene-dense and contains most core genes, while the B-compartment is more repeat-rich and has higher rates of chromosomal rearrangement. While the B-compartment is transcriptionally repressed, it has significantly more secreted proteins and in Planta up-regulated candidate effectors, suggesting a possible host-induced change in chromosome conformation. Overall, this study provides a fine-scale view into the genome biology and evolution of prominent Plant Symbionts, and opens avenues to study the mechanisms that generate and modify chromosome folding during host-microbe interactions.
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homo and dikaryons of the arbuscular mycorrhizal fungus rhizophagus irregularis differ in life history strategy
Frontiers in Plant Science, 2021Co-Authors: Edward Umberto Serghi, Vasilis Kokkoris, Calvin Cornell, Jeremy Dettman, Franck Stefani, Nicolas CorradiAbstract:Arbuscular mycorrhizal fungi (AMF) are obligate Plant Symbionts that have the potential to improve crop yield. These multinucleate organisms are either homokaryotic (AMF homokaryons) or heterokaryotic (AMF dikaryons). In AMF dikaryons thousands of nuclei originating from two parental strains co-exist in the cytoplasm. In other fungi, homokaryotic and dikaryotic strains show distinct life history traits (LHT) such as variation in growth speed and fitness, but how such traits compare between AMF dikaryons and homokaryotic relatives is unknown. To address this, we measured 20 life history traits across three root organ cultures (Carrot, Chicory, Nicotiana) for 10 phylogenetically distinct strains (four dikaryons, six homokaryons) of the model species R. irregularis. Our analyses show that AMF dikaryons have clearly distinct life history strategies (LHS) compared to AMF homokaryons. In particular, while AMF homokaryons have significantly higher germination ability and germinate faster, AMF dikaryons grow significantly faster and create a more complex hyphal network post-germination across hosts. These findings link nuclear organization with the emergence of key ecological and evolutionary traits in a widespread group of multinucleate Plant Symbionts.
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Fungal Mating in the Most Widespread Plant Symbionts
Trends in plant science, 2016Co-Authors: Nicolas Corradi, Andreas BrachmannAbstract:Arbuscular mycorrhizal fungi (AMF) are relevant Plant Symbionts whose hyphae and spores carry hundreds of coexisting nuclei with supposedly divergent genomes but no sign of sexual reproduction. This unusual biology suggested that conventional fungal mating is not amendable to optimize strains for Plant growth, but recent evidence of sexual-related nuclear inheritance in these organisms is now challenging this widespread notion. Here, we outline our knowledge of AMF genetics within a historical context, and discuss how past and new information in this area changed our understanding of AMF biology. We also highlight the mating-related processes in AMF, and propose new research avenues and approaches that could lead to a better application of these organisms for agricultural and environmental practices.
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Extreme diversification of the mating type-high-mobility group (MATA-HMG) gene family in a Plant-associated arbuscular mycorrhizal fungus
New Phytologist, 2014Co-Authors: Rohan Riley, Philippe Charron, Laurent Farinelli, Yolande Dalpé, Francis Martin, Alexander Idnurm, Nicolas CorradiAbstract:Arbuscular mycorrhizal fungi (AMF) are important Plant Symbionts that have long been considered evolutionary anomalies because of their apparent long-term lack of sexuality, but recent explorations of available DNA sequence have challenged this notion by revealing the presence of homologues of fungal mating type-high-mobility group (MATA-HMG) and core meiotic genes in these organisms. To obtain more insights into the sexual potential of AMF, homologues of MATA-HMGs were sought in the transcriptome of three AMF isolates, and their functional and evolutionary trajectories were studied in genetically divergent strains of Rhizophagus irregularis using conventional and quantitative PCR procedures. Our analyses revealed the presence of at least 76 homologues of MATA-HMGs in R.irregularis isolates. None of these was found to be surrounded by genes generally found near other known fungal mating type loci, but here we report the presence of a 9-kb-long region in the AMF R.irregularis harbouring a total of four tandem-repeated MATA-HMGs; a feature that highlights a potentially elevated intragenomic diversity in this AMF species. The present study provides intriguing insights into the genome evolution of R.irregularis, and represents a stepping stone for understanding the potential of these fungi to undergo cryptic sex.
Marcel G.a. Van Der Heijden - One of the best experts on this subject based on the ideXlab platform.
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community assembly species richness and nestedness of arbuscular mycorrhizal fungi in agricultural soils
Molecular Ecology, 2012Co-Authors: Erik Verbruggen, Marcel G.a. Van Der Heijden, James T Weedon, George A Kowalchuk, Wilfred F M RolingAbstract:Understanding how communities assemble is a central goal of ecology. This is particularly relevant for communities of arbuscular mycorrhizal fungi (AMF), because the community composition of these beneficial Plant Symbionts influences important ecosystem processes. Moreover, AMF may be used as sensitive indicators of ecological soil quality if they respond to environmental variation in a predictable way. Here, we use a molecular profiling technique (T-RFLP of 25S rRNA gene fragments) to test which factors determine AM fungal community composition in 40 agricultural soils in the Netherlands. In particular, we test whether species richness, dominance structure and community nestedness are influenced by management type (in pairs of organically and conventionally farmed fields), and we examine the contribution of crop species (maize vs. potato), soil type (sand vs. clay-textured soils) and habitat (Plant root vs. bulk soil) on AMF community characteristics. AMF richness varied from 1 to 11 taxa per field. Communities from species-poor fields were found to be subsets of those in richer fields, indicating nestedness and a progressive ‘loss’ from the species pool. AMF taxa richness and occurrence in soil and Plant roots were highly correlated, and richness was related to management intensity (phosphate availability and grass-cropping history together explained 32% and 50% of richness in roots and soils). Soil type together with soil chemical parameters explained only 17% of variance in AMF community structure. We synthesize these results by discussing the potential contribution of a ‘bottleneck effect’ on AMF communities through increased stochastic effects under environmental stress.
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belowground biodiversity effects of Plant Symbionts support aboveground productivity
Ecology Letters, 2011Co-Authors: Cameron Wagg, Jan Jansa, Bernhard Schmid, Marcel G.a. Van Der HeijdenAbstract:Soil microbes play key roles in ecosystems, yet the impact of their diversity on Plant communities is still poorly understood. Here we demonstrate that the diversity of belowground Plant-associated soil fungi promotes Plant productivity and Plant coexistence. Using additive partitioning of biodiversity effects developed in Plant biodiversity studies, we demonstrate that this positive relationship can be driven by complementarity effects among soil fungi in one soil type and by a selection effect resulting from the fungal species that stimulated Plant productivity the most in another soil type. Selection and complementarity effects among fungal species contributed to improving Plant productivity up to 82% and 85%, respectively, above the average of the respective fungal species monocultures depending on the soil in which they were grown. These results also indicate that belowground diversity may act as insurance for maintaining Plant productivity under differing environmental conditions.
Matteo Lorito - One of the best experts on this subject based on the ideXlab platform.
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trichoderma species opportunistic avirulent Plant Symbionts
Nature Reviews Microbiology, 2004Co-Authors: Gary E Harman, Charles R Howell, Ada Viterbo, Ilan Chet, Matteo LoritoAbstract:Trichoderma spp. are free-living fungi that are common in soil and root ecosystems. Recent discoveries show that they are opportunistic, avirulent Plant Symbionts, as well as being parasites of other fungi. At least some strains establish robust and long-lasting colonizations of root surfaces and penetrate into the epidermis and a few cells below this level. They produce or release a variety of compounds that induce localized or systemic resistance responses, and this explains their lack of pathogenicity to Plants. These root–microorganism associations cause substantial changes to the Plant proteome and metabolism. Plants are protected from numerous classes of Plant pathogen by responses that are similar to systemic acquired resistance and rhizobacteria-induced systemic resistance. Root colonization by Trichoderma spp. also frequently enhances root growth and development, crop productivity, resistance to abiotic stresses and the uptake and use of nutrients.