Project description:Background: The soil environment is responsible for sustaining most terrestrial plant life on earth, yet we know surprisingly little about the important functions carried out by diverse microbial communities in soil. Soil microbes that inhabit the channels of decaying root systems, the detritusphere, are likely to be essential for plant growth and health, as these channels are the preferred locations of new root growth. Understanding the microbial metagenome of the detritusphere and how it responds to agricultural management such as crop rotations and soil tillage will be vital for improving global food production. Methods: The rhizosphere soils of wheat and chickpea growing under + and - decaying root were collected for metagenomics sequencing. A gene catalogue was established by de novo assembling metagenomic sequencing. Genes abundance was compared between bulk soil and rhizosphere soils under different treatments. Conclusions: The study describes the diversity and functional capacity of a high-quality soil microbial metagenome. The results demonstrate the contribution of the microbiome from decaying root in determining the metagenome of developing root systems, which is fundamental to plant growth, since roots preferentially inhabit previous root channels. Modifications in root microbial function through soil management, can ultimately govern plant health, productivity and food security.
Project description:Arsenic (As) bioavailability in the rice rhizosphere is influenced by many microbial interactions, particularly by metal-transforming functional groups at the root-soil interface. This study was conducted to examine As-transforming microbes and As-speciation in the rice rhizosphere compartments, in response to two different water management practices (continuous and intermittently flooded), established on fields with high to low soil-As concentration. Microbial functional gene composition in the rhizosphere and root-plaque compartments were characterized using the GeoChip 4.0 microarray. Arsenic speciation and concentrations were analyzed in the rhizosphere soil, root-plaque, porewater and grain samples. Results indicated that intermittent flooding significantly altered As-speciation in the rhizosphere, and reduced methyl-As and AsIII concentrations in the pore water, root-plaque and rice grain. Ordination and taxonomic analysis of detected gene-probes indicated that root-plaque and rhizosphere assembled significantly different metal-transforming functional groups. Taxonomic non-redundancy was evident, suggesting that As-reduction, -oxidation and -methylation processes were performed by different microbial groups. As-transformation was coupled to different biogeochemical cycling processes establishing functional non-redundancy of rice-rhizosphere microbiome in response to both rhizosphere compartmentalization and experimental treatments. This study confirmed diverse As-biotransformation at root-soil interface and provided novel insights on their responses to water management, which can be applied for mitigating As-bioavailability and accumulation in rice grains.
Project description:The experiment was designed to test the interactions of Spartina alterniflora, its microbiome, and the interaction of the plant-microbe relationship with oil from the Deepwater Horizon oil spill (DWH). Total RNA was extracted from leaf and root microbiome of S. alterniflora in soils that were oiled in DWH oil spill with or without added oil, as well as those grown in unoiled soil with or without added oil. The work in its entirety characterizes the transport, fate and catabolic activities of bacterial communities in petroleum-polluted soils and within plant tissues.
Project description:Opioids such as morphine have many beneficial properties as analgesics, however, opioids may induce multiple adverse gastrointestinal symptoms. We have recently demonstrated that morphine treatment results in significant disruption in gut barrier function leading to increased translocation of gut commensal bacteria. However, it is unclear how opioids modulate the gut homeostasis. By using a mouse model of morphine treatment, we studied effects of morphine treatment on gut microbiome. We characterized phylogenetic profiles of gut microbes, and found a significant shift in the gut microbiome and increase of pathogenic bacteria following morphine treatment when compared to placebo. In the present study, wild type mice (C57BL/6J) were implanted with placebo, morphine pellets subcutaneously. Fecal matter were taken for bacterial 16s rDNA sequencing analysis at day 3 post treatment. A scatter plot based on an unweighted UniFrac distance matrics obtained from the sequences at OTU level with 97% similarity showed a distinct clustering of the community composition between the morphine and placebo treated groups. By using the chao1 index to evaluate alpha diversity (that is diversity within a group) and using unweighted UniFrac distance to evaluate beta diversity (that is diversity between groups, comparing microbial community based on compositional structures), we found that morphine treatment results in a significant decrease in alpha diversity and shift in fecal microbiome at day 3 post treatment compared to placebo treatment. Taxonomical analysis showed that morphine treatment results in a significant increase of potential pathogenic bacteria. Our study shed light on effects of morphine on the gut microbiome, and its role in the gut homeostasis.
Project description:<p>Drought stress negatively impacts microbial activity, but the magnitude of stress responses are likely dependent on a diversity of below ground interactions. Populus trichocarpa individuals and no plant bulk soils were exposed to extended drought (~0.03% gravimetric water content (GWC) after 12d), re-wet, and a 12-d 'recovery' period to determine the effects of plant presence in mediating soil microbiome stability to water stress. Plant metabolomic analyses indicated that drought exposure increased host investment in C and N metabolic pathways (amino acids, fatty-acids, phenolic glycosides) regardless of recovery. Several metabolites positively correlated with root-associated microbial alpha diversity, but not those of soil communities. Soil bacterial community composition shifted with P. trichocarpa presence and with drought relative to irrigated controls, whereas soil fungal composition only shifted with plant presence. However, root fungal communities strongly shifted with drought, whereas root bacterial communities changed to a lesser degree. The proportion of bacterial water-stress opportunistic OTUs (enriched counts in drought) were high (~11%) at the end of drying phases, and maintained after re-wet, and recovery phases in bulk soils, but declined over time in soils with plants present. For root fungi opportunistic OTUs were high at the end of recovery in drought treatments (~17% abundance), although relatively not responsive in soils, particularly planted soils (< 0.5% abundance for sensitive or opportunistic). These data indicate that plants modulate soil and root associated microbial drought responses via tight plant-microbe linkages during extreme drought scenarios, but trajectories after extreme drought vary with plant habitat and microbial functional groups.</p>
Project description:Sorghum bicolor is one of the most important cereal crops in the world, predominantly grown in sub‑Saharan Africa by smallholder farmers. Despite its outstanding resilience to abiotic stresses, approximately 20% of sorghum yield is annually lost on the African continent due to infestation with the parasitic weed Striga hermonthica. Existing Striga management strategies to decrease Striga infestation often show low efficiency and are not easily integrated into current agricultural practices. Microbial-based solutions may prove an effective, low-cost mode for reducing Striga parasitism in sub-Saharan Africa. Here, we demonstrate that the microbiome component of a field soil suppresses Striga infection of sorghum. Potential mechanisms underlying the soil microbiome’s influence on the host plant include root endodermal suberization and aerenchyma formation. Moreover, we observed a depletion of haustorium inducing factors, compounds essential for Striga to establish the host-parasite association, in root exudates collected from sorghum grown in the presence of the soil microbiome as compared to sterile conditions. We further identified individual microbial taxa associated with reduced Striga infection via changes in root cellular anatomy and differentiation as well as in exudate composition. Our study identifies a suite of traits that can be harnessed by individual microbial isolates or their consortia to induce Striga resistance. Combining microbes that elicit Striga resistance directly (affecting the parasite) via repression of haustorium formation with those that act indirectly (affecting the host), by reducing of Striga penetration through root tissue, can broaden the effectiveness of microbe-induced protection from Striga.
Project description:The rhizosphere is a small region surrounding plant roots that is enriched in biochemicals from root exudates and populated with fungi, nematode, and bacteria. Interaction of rhizosphere organisms with plants is mainly promoted by exudates from the roots. Root exudates contain biochemicals that come from primary and secondary metabolisms of plants. These biochemicals attract microbes, which influence plant nutrition. The rhizosphere bacteria (microbiome) are vital to plant nutrient uptake and influence biotic and abiotic stress and pathogenesis. Pseudomonas is a genus of gammaproteobacteria known for its ubiquitous presence in natural habitats and its striking ecological, metabolic, and biochemical diversity. Within the genus, members of the Pseudomonas fluorescens group are common inhabitants of soil and plant surfaces, and certain strains function in the biological control of plant disease, protecting plants from infection by soilborne and aerial plant pathogens. The soil bacterium Pseudomonas protegens Pf-5 (also known as Pseudomonas fluorescens Pf-5) is a well-characterized biological strain, which is distinguished by its prolific production of the secondary metabolite, pyoverdine. Knowledge of the distribution of P. fluorescens secretory activity around plant roots is very important for understanding the interaction between P. fluorescens and plants and can be achieved by real time tracking of pyoverdine. To achieve the capability of real-time tracking in soil, we have used a structure-switching SELEX strategy to select high affinity ssDNA aptamers with specificity for pyoverdine over other siderophores. Two DNA aptamers were isolated, and their features compared. The aptamers were applied to a nanoporous aluminum oxide biosensor and demonstrated to successfully detect PYO-Pf5. This sensor provides a future opportunity to track the locations around plant roots of P. protegens and to monitor PYO-Pf5 production and movement through the soil.
Project description:The cotyledons of etiolated seedlings from terrestrial flowering plants must emerge from the soil surface, while roots must penetrate the soil to ensure plant survival. We show here that the soil emergence related transcription factor PHYTOCHROME-INTERACTING FACTOR 3 (PIF3) regulates root penetration via transducing external signals perceived by the receptor kinase FERONIA (FER) in Arabidopsis thaliana. The loss of FER function in the fer-4 mutant resulted in a severe defect in root penetration into hard soil or medium. Single-cell RNA-seq profiling of roots revealed a distinct cell clustering pattern, especially for root cap cells, and revealed PIF3 as a putative FER-regulated transcription factor. Biochemical, imaging, and genetic experiments confirmed that PIF3 is required for root soil penetration. Moreover, FER interacted with and stabilized PIF3, which then modulated the expression of mechanosensitive ion channels and the sloughing of outer cells in the root cap. We propose a novel mechanism of soil penetration by plant roots.
Project description:Plants are naturally associated with diverse microbial communities, which play significant roles in plant performance, such as growth promotion or fending off pathogens. The roots of Alkanna tinctoria L. are rich in naphthoquinones, particularly the medicinally used chiral compounds alkannin, shikonin and their derivatives. Former studies already have shown that microorganisms may modulate plant metabolism. To further investigate the potential interaction between A. tinctoria and associated microorganisms we performed a greenhouse experiment, in which A. tinctoria plants were grown in the presence of three distinct soil microbiomes. At four defined plant developmental stages we made an in-depth assessment of bacterial and fungal root-associated microbiomes as well as all primary and secondary metabolites. Our results showed that the plant developmental stage was the most important driver influencing the plant metabolite content, revealing peak contents of alkannin/shikonin at the fruiting stage. In contrast, the soil microbiome had the biggest impact on the plant root microbiome. Correlation analyses performed on the measured metabolite content and the abundance of individual bacterial and fungal taxa suggested a dynamic, at times positive or negative relationship between root-associated microorganisms and root metabolism. In particular, the bacterial Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium group and the fungal species Penicillium jensenii were found to be positively correlated with higher content of alkannins.
Project description:<div>Species-rich plant communities can induce unique soil biotic legacy effects through changing the abundance and composition of soil biota. These soil legacy effects can cause feedbacks to influence plant performance. In addition, soil biota can induce (defensive) secondary metabolites in shoots and roots and thus affect plant-herbivore interactions. We hypothesize that plant diversity-driven soil biotic legacy effects elicit changes in the shoot and root metabolome. <br></div><div><br></div><div>We tested this hypothesis by establishing an experiment with four plant species. We grew plants in a sterile substrate inoculated with soil conditioned by different plant species communities: (1) monocultures of either of the four species, (2) the four species in a mixture, (3) an eight species mixture including all four species, or (4) a sterile inoculum. After at least eight weeks in the field, we estimated shoot herbivory. At the same time, we took root and shoot samples for metabolomics analyses by liquid chromatography quadrupole time-of-flight mass spectrometry. <br></div><div><br></div><div>We found that shoot and root metabolomes of all plants grown in sterile soil differed significantly from those grown in living soil. The plant metabolomes in living soils differed by species and tissue. Across all species, shoots displayed a greater richness of secondary metabolites than roots. The richness of secondary metabolites differed by species and among living soils. The conditioning species richness significantly affected the Shannon diversity of secondary metabolites in Centaurea jacea. Shoot herbivory positively correlated with the richness and Shannon diversity of secondary metabolites in Leucanthemum vulgare. We detected multiple metabolites that together explained up to 88% of the variation in herbivory in the shoots of Centaurea jacea and Plantago lanceolata. <br></div><div><br></div><div>Synthesis: Our findings suggest that plant diversity-driven shifts in soil biota elicit changes in the composition and diversity of shoot and root secondary metabolites. However, these plant responses and their effect on shoot herbivores are species-specific. Tracking changes in plant secondary chemistry in response to soil biotic legacy effects will help to understand the mechanisms that govern species-specific plant-plant and plant-herbivore interactions.</div>